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THE GREEN CRAB INVASION:
A GLOBAL PERSPECTIVE,
WITH LESSONS FROM WASHINGTON STATE

by
Debora R. Holmes

A Thesis: Essay ofDistinction
submitted in partial fulfillment
of the requirements for the degree
Master of Environmental Studies
The Evergreen State College
September 2001

This Thesis for the Master of Environmental Studies Degree
by

Debora R. Holmes

has been approved for
The Evergreen State College
by

Member of the Faculty

'S"f\:

1 '> 'o I
Date

For Maria Eloise: may you grow up learning and loving trails and shores

ABSTRACT
The Green Crab Invasion: A Global Perspective,
With Lessons from Washington State
Debora R. Holmes
The European green crab, Carcinus maenas, has arrived on the shores of
Washington State. This recently-introduced exotic species has the potential for
great destruction. Green crabs can disperse over large areas and have serious
adverse effects on fisheries and aquaculture; their impacts include the
possibility of altering the biodiversity of ecosystems. When the green crab was
first discovered in Washington State in 1998, the state provided funds to
immediately begin monitoring and control efforts in both the Puget Sound
region and along Washington's coast. However, there has been debate over
whether or not to continue funding for these programs.
The European green crab has affected marine and estuarine ecosystems,
aquaculture, and fisheries worldwide. It first reached the United States in
1817, when it was accidentally introduced to the east coast. The green crab
spread to the U.S. west coast around 1989 or 1990, most likely as larvae in
ballast water from ships. It is speculated that during the El Ni:fio winter of
1997-1998, ocean currents transported green crab larvae north to Washington
State, where the first crabs were found in the summer of 1998. Green crabs
have now been found in Washington's two major coastal bays, Willapa Bay
and Grays Harbor, and there is fear that they may spread to the Puget Sound
regiOn.
Field observations and laboratory experiments have shown that the European
green crab both consumes and competes with a vast array of organisms,
including clams, oysters, mussels, snails, and other crabs. On an economic
level, a widespread green crab invasion could severely injure Washington
State's oyster, clam, mussel, and Dungeness crab industries, among others.
The biodiversity oflocal ecosystems could also be affected, with impacts on
sensitive species of concern. Upon examination, I have found ten such
sensitive species that will become increasingly vulnerable with each new
influx of green crabs.
Means of addressing the green crab problem are varied, and include prevention
measures, early detection (monitoring), trapping, keeping crabs out of specific
areas, pesticides, bounty programs, fisheries, volunteer programs, public
education, biological control, genetic alteration, and government incentives. It
can be expected that future recruitment of green crabs will occur, but the scope
and timing of such recruitment events are difficult to predict. Currently,
Washington State's focus is on trapping existing populations of green crabs,

preventing more green crabs from entering state marine ecosystems, and
detecting new populations as quickly as possible.
The State of Washington is to be commended for its far-sighted handling of
this problem, and may serve as a model for other regions in their handling of
invasive marine species. If detection and control does not continue to be
implemented, the result will be an exotic species invasion that could not only
alter Washington State's marine and estuarine environments, but also cause
annual economic losses of up to $24 million dollars.

TABLE OF CONTENTS

LIST OF FIGURES .................................................................. vi

LIST OF TABLES .................................................................. vii

ACKNOWLEDGMENTS ......................................................... viii

INTRODUCTION .................................................................... 1

NON-NATIVE SPECIES AND THEIR IMPACTS IN THE UNITED
STATES ................................................................................ 3

CARCINUS MAENAS, THE GREEN CRAB ..................................... 6
History of the green crab ................................................... 6
Green crabs have arrived in Washington State .......................... 8
Physical characteristics of green crabs ................................... 11
Reproduction and life cycle ................................................ 15

THE GREEN CRAB PROBLEM ................................................. 16
Deleterious ecological effects of green crabs ........................... 16
Deleterious economic effects of green crabs ............................ 20
Additional impacts upon biodiversity in Washington State ........... 27

PREVENTING, DETECTING, AND CONTROLLING GREEN
CRABS ................................................................................ 36
Introduction .................................................................. 36
Prevention measures ........................................................ 36
iv

Early detection (monitoring) ............................................... 39
Trapping ................... ·-· ................................................. 43
Keeping crabs out of specific areas ...................................... .49
Use of carbaryl as a pesticide ............................................. .49
Bounty programs ............................................................ 52
Fisheries ....................................................................... 56
Volunteer programs ......................................................... 57
Public education ............................................................. 60
Biological control. ........................................................... 63
Genetic alteration ............................................................ 69
Can we predict future recruitment? ....................................... 70
A word on government incentives ........................................ 71

CURRENT STATUS OF WASHINGTON STATE'S GREEN CRAB
POPULATION AND RESPONSE ................................................ 73
Population status ............................................................ 73
Funding for green crab programs .......................................... 80

CONCLUSIONS: LESSONS FROM WASHINGTON STATE'S
EXPERIENCE ........................................................................ 83

RECOMMENDATIONS ............................................................ 87

BIBLIOGRAPHY .................................................................... 94

This thesis is printed on paper made from 100% post-consumer pulp
produced in a chlorine-free pulping and bleaching process,

v

FIGURES

Figure
1. Estimated dates of introduction ofthe European green crab along the U.S.

west coast ................................................................................. 9
2. Adult European green crab (Carcinus maenas) .................................... l3
3. Representative monitoring sites for the European green crab in the Puget
Sound region of Washington State, 1999-2001 ................................. 41
4. Washington Department ofFish and Wildlife green crab survey effort,
Willapa Bay and Grays Harbor, Washington, 1998-2001 .................... .46
5. Catch per unit effort (CPUE) of European green crabs caught by the
Washington Department ofFish and Wildlife in Willapa Bay, Washington,
1998-2000, and in Grays Harbor, Washington, 1999-2000 ................. .47
6. Advertisement alerting public to the problem of introducing non-native
species into state waters ............................................................... 62

7. Sizes of green crabs found in Willapa Bay, Washington, for years 1998 2000 ..................................................................................... 78
8. Sizes of green crabs found in Grays Harbor, Washington, for years 19982000 ..................................................................................... 79

VI

TABLES

Table
1. Washington priority species potentially vulnerable to the European green
crab .............................................................................. ~ ........ 29
2. Numbers and genders of green crabs caught in Willapa Bay and Grays
Harbor, Washington, from 1998 to 2000 ........................................... 76
3. Recommendations for future green crab control and monitoring efforts in
Washington State ...................................................................... 93

Vll

ACKNOWLEDGMENTS

This is the last piece of my thesis I write, and I've been looking forward to it.
TO:
my strange and wonderful friends at school, in Olympia, and in Seattle ... you
know who you are.
the faculty and staff in the MES program at The Evergreen State College, who
ensured that my 2-year stay here was not only productive, but enjoyable.
the unflappable Dave Milne, my thesis reader-you made this thing rather fun (at
times)-thanks for the guidance.
John Perkins, for all the teaching, direction, and good humor.
the good people who deal with green crabs every day at the Washington
Department ofFish and Wildlife-Brett Dumbauld, Ron Figlar-Bames, Andrea
Randall, Russell Rogers, Pam Meacham, Scott Smith, and Christine Sato, my old
Spartina buddy-! am deeply in your debt for all the help, data, communication,
and encouragement.
Sylvia Behrens Yamada, who graciously provided me with a lion's share ofuseful
green crab information.
Amy Boatright and Russell Rogers for proofreading this whole thing religiously,
and to Jen, who volunteered to, but Amy beat her to it.
Ken Jacobsen, Washington State Senator, for being a champion in the fight.
the Mariners-you've made me very proud.
Alpha, the sheltie-mix who understood grad school better than I did, I miss you;
Guinevere, you are the best toy poodle in the world, thanks for not barking.
my brother, Tom, and his Sue. I didn't do it. You did it.
my parents, Dave and Darlene, who always thought everything I did was great,
look-I just wrote a whole book.
and finally, to Jim, who has hardly known me as anything other than a graduate
student, with all my love.
To Minnesota, and my extended family, you don 't have any marine nuisance
species, but I love you anyway.
To Washington, now that you have me, I could never leave.
vm

INTRODUCTION

The European green crab, Carcinus maenas (L. 1758) is a recent arrival to
the shores ofWashington State. Its potential for destruction is immense. An
invasive species such as the green crab can disperse over large areas, negatively
influencing many other species and affecting aquaculture, fisheries, and even
recreational fishing. At times the biodiversity of a region may be critically altered
by such species. Often, the invaders displace indigenous species, some ofwhich
have a tenuous foothold to begin with due to other factors such as pollution
(Richter et al. 1997). If and when a large-scale invasion of green crabs occurs in
the State of Washington, the disruption they cause may lead to alterations of
entire ecosystems, and damage may be far-reaching.

When the European green crab was first discovered in Washington State in
1998, the state provided funds to immediately begin monitoring and control
efforts in both the Puget Sound region and on Washington's coast. However, in
spite of the fact that small numbers of green crabs have been found in
Washington's two largest bays--or perhaps because of the fact that these numbers
are small-there has been debate over whether or not to continue funding for
green crab detection and control. It is my opinion that if prevention, detection,
and control strategies do not continue to be implemented here, the result may be
an alien species invasion that could greatly alter our marine and estuarine
environments. This is not only an important issue for commercial aquaculture,
1

but for biodiversity in general, with possible severe implications for endangered,
threatened, and other sensitive species as well.

This thesis addresses the problems that green crabs can cause, both in the
State ofWashington and around the world, and looks at different methods of
prevention, monitoring, and control. It also provides an analysis ofWashington
State's handling of the green crab invasion to date, including recommendations
for the future, based upon these findings.

2

NON-NATIVE SPECIES AND THEIR IMPACTS IN THE U.S.

Why do so many plant and animal species populations reach critically low
levels and end up on endangered, threatened, and other lists of concern? E. 0.
Wilson has been one of the first scientists to provide a comprehensive view.
Writing on the vast numbers of plant and animal species that have become
endangered, Wilson (1992) states that the spread of alien species is second only to
habitat destruction as a cause. In an overall analysis in which they sought to
determine what most affects imperiled species in the United States, Wilcove et al.
(1998) also report that " ... competition with or predation by alien species ... " was
second only to habitat destruction as a threat. In their study of2,490 U.S.
imperiled species, they found that this competition with (or predation by) alien
species had affected 49% of all species they studied. This percentage covers a
variety of plants, mammals, birds, reptiles, amphibians, fishes, mussels, crayfish,
beetles, butterflies, and various other invertebrates. Yet another tally indicates
that on the U.S. Department of the Interior's endangered or threatened species
lists, 40% of those species listed are at risk primarily because of threats by nonindigenous species (Pimentel1999).

With regard to aquatic species nationwide, Richter et al. (1997) found the
three leading threats to be agricultural non-point pollution, alien species, and
altered hydrologic regimes. In addition, they found that in the western part of the
United States, the dominant threat to aquatic species is that posed by alien species.
3

They attribute this in part to the ecological sensitivities of eastern versus western
species (Richter et al. 1997). In one comprehensive study of the U.S. west coast,
Cohen and Carlton (1995) add that introductions of alien marine species have
been increasing in the San Francisco estuary in recent years, a scenario not at all
uncommon in western bays and estuaries.

The economic costs of non-native species invasions in the United States
are also staggering. Non-native species may invade everything from gardens to
agricultural fields, as well as natural areas such as wetlands, forests, grasslands,
and marine/estuarine environments. Economic losses from such invasions and
their subsequent effects are normally estimated to be at least several billion dollars
per year (Environmental Inquiry 2001). In one study, Pimentel et al. (2000)
estimated that the invasion of exotic weeds and plant pests alone costs the United
States $80 billion every year. Total annual losses caused by invasive exotic
species in the U.S. are estimated to be $137 billion (Pimentel et al. 2000).

Thus, agreement is widespread that exotic species introductions are
increasing, and that these invasions significantly endanger indigenous species and
cost the United States an astronomical amount in terms of economic losses. And
what is to be done about the issue of invasive species? Perhaps the examination
of one specific species' invasion, along with a discussion of past and present
attempts to confront it, can yield some clues and possibly serve as a model for

4

future attempts to control invasive species or to prevent their introductions
altogether.

5

CARCINUS MAENAS, THE GREEN CRAB

The invasive species of which I speak-a recent, accidental introduction to
the United States' west coast-is the European green crab, Carcinus maenas.
Fishermen in the San Francisco Bay area, the site of the green crab's first west
coast establishment, reported finding green crabs in their traps as early as 1989 or
1990 (Cohen and Carlton 1995). In a few short years, the numbers of green crabs
in the area had reached epidemic proportions. In the San Francisco estuary today,
it is common for green crabs to be caught in shrimp nets and in bait fish traps,
where sometimes hundreds of crabs fill each trap (Cohen and Carlton 1995).

Green crabs are found in salinities of 4-52 ppt (parts per thousand),
temperatures down to freezing, and in virtually all types of protected and semiprotected marine and estuarine habitats, including mud, sand, rock, cordgrass
marshes, and eelgrass beds. To make matters worse, green crabs are quite
prolific, with females spawning up to 185,000 eggs at a time under favorable
conditions (Cohen and Carlton 1995). Since these crabs have such wide
environmental tolerances, it is estimated that their range could eventually stretch
from Baja California to Alaska (Carlton and Cohen 1995; Cohen et al. 1995).

History of the green crab
The green crab, a common shore crab in Europe, is native to the shores of
the eastern Atlantic, the North Sea and eastern Baltic Sea, and may be found from
6

its native range ofNorway and the British Isles all the way south to Mauritania,
northern Africa (Behrens Yamada, unpublished manuscript; Washington
Department ofFish and Wildlife 2001a). European green crabs arrived as an
invasive species in Australia around 1900, most likely as stowaways in beach
rocks used as semi-dry ballast in English ships (Thresher 1997). Green crabs
made their first appearance in South Africa in 1983 (LeRoux et al. 1990) and
established a large population there, as they have also done in Japan (1984) and
South America. Carcinus maenas has even been found in Thailand, but its
attempted invasion there uncharacteristically failed (Thresher 1997).

Green crabs were first found on the United States' Atlantic coast in 1817
(Say 1817). Carcinus maenas did not, however, manage to reach the Pacific coast
until somewhere around 1989 (the exact date is unclear). At that time, the most
likely mode of transport was as larvae in ballast water, although adults may have
been present in algae used to pack New England bait worms or lobsters. The
crabs may also have been transported in the seawater pipe systems of ships or
released as discarded research material (Carlton and Cohen 1995; Cohen et al.
1995).

As stated earlier, the green crab's first establishment on the U.S. west
coast was in the San Francisco Bay and delta area, where crabs were first reported
around 1989. However, it is believed by some that these crabs were present in the
area much earlier, and had been building up numbers in warm lagoons and
7

sloughs before dispersing into the rest of the bay (Cohen et al. 1995, as cited by
Behrens Yamada, unpublished manuscript). From this point on the California
coast, the green crab expanded in both southerly and northerly directions along
the U.S. west coast, and is presently found as far south as Morro Bay, California,
and as far north as Lemmens Inlet near Totino, Vancouver Island, British
Columbia, where it landed in 1998 (Behrens Yamada, unpublished manuscript).
Figure 1 maps the areas on the U.S. west coast where the green cnib has been
found so far, along with the estimated dates of introduction. As one can see from
this map, the northward expansion of the green crab has been much greater than
the southward spread, despite prevailing southerly currents.

Although Cohen and Carlton (1995) state that green crabs have been found
in virtually all types of protected and semi-protected marine and estuarine
habitats, there is one interesting exception: on the U.S. west coast, green crabs
have not normally been seen on exposed rocky shores, although they have been
found in that habitat elsewhere in the world (Behrens Yamada, unpublished
manuscript; Milne, personal communication).

Green crabs have arrived in Washington State
On June 9, 1998, in Washington's Willapa Bay, an employee from the
state Department of Natural Resources and a scientist from California stumbled
across one lone crab shell that did not look quite right. Unfortunately, it was
confirmed to be the shell of a young, male European green crab. On the 21st of

8

1100

130"
CANADA

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1998
Washington

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/ 011''i\P'""

Oregon

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1993

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1993

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2QOL---~~--------------L---------------L---------------~

Figure 1. Estimated dates of introduction of the European Green Crab
along the U.S. west coast. (Map modified from Behrens Yamada,
unpublished manuscript)

9

July, the Washington Department ofFish and Wildlife (WDFW) announced that
11 green crabs had been captured that day in Grays Harbor. And so, the fight was
on.

It is currently believed that the green crab's vector of introduction to

Washington State was "most likely a matter of simple larval transport"
(Dumbauld, personal communication). Ocean currents flowing northward from
California and Oregon, the source regions of the west coast green crab population,
were thought to have been especially good in facilitating transport of the crab
larvae that year. Though probably related to the El Nifio event of 1997-98
(Behrens Yamada, unpublished manuscript), which is a somewhat less-thancommon occurrence, the fact remains that the crabs are now in Washington. On
February 5, 1999, the first discovery of a female green crab with eggs-by a local
oyster grower in Willapa Bay-was made, proving that green crabs are indeed
breeding in Washington's bays (Washington Department ofFish and Wildlife
1998-2000b).

Green crabs have been found in Washington's two major coastal bays,
Willapa Bay and Grays Harbor (see Figure 1). Although the Puget Sound region
is only being monitored for any potential newcomer crabs at this point in time,
trapping programs coordinated and run by the Washington Department ofFish
and Wildlife were promptly set up in the two coastal bays as soon as the green
crab was detected in those regions (Dumbauld, personal communication). As of
10

the end ofthe year 2000, 796live green crabs had been collected at Willapa Bay,
and 230 in Grays Harbor, where the trapping was less extensive (Washington
Department ofFish and Wildlife 1998-2000a; Washington Department ofFish
and Wildlife 1998-2000b). Declines in the catch have been noted since 1998. It
is unknown whether this is due more to the state's trapping programs or to lack of
substantial new recruitment (Dumbauld, personal communication), but most
likely it is a combination ofboth (Rogers 2001a).

Ironically, Dumbauld (personal communication) indicates that the
presence of green crabs is highly correlated with the presence of Spartina

alterniflora, the invasive cordgrass so prevalent in Washington's Willapa Bay.
This is probably not surprising, given the fact that green crabs have been
associated with tidal salt marshes (along with shellfish beds), habitats where

Spartina also flourishes and where larger native crabs like the Dungeness crab are
less abundant (Dumbauld, personal communication; Washington Department of
Fish and Wildlife 2001a).

Physical characteristics of green crabs
In spite of their name, green crabs are not consistently green. They vary in
color, which may change from green to orange and then red during molting
cycles. Yellow, orange, and red coloration may be displayed on the underside of
the green crab. Because of these color variations and the fact that many native
crabs can be green, it is generally not a good idea to use color as a distinguishing
11

characteristic when attempting to identify green crabs (Washington Department of
Fish and Wildlife 2001a).

For simplicity in describing European green crabs, they have been further
placed into two groups associated with color phase: green crabs and red crabs
(Kaiser et al. 1990, as cited by McKnight et al. 2000). Red-colored individuals,
which tend to be bigger, have been found to prefer larger bivalves, exert more
force with their crusher claws, and win more disputes over prey than the greencolored version of the European green crab (Kaiser et al. 1990, as cited by
McKnight et al. 2000; McKnight et al. 2000; Washington Department ofFish and
Wildlife 2001a).

Five evenly spaced triangular teeth, or spines, are found on each side of
the green crab shell, or carapace, behind the eye (see Figure 2). This feature sets
the green crab apart from native crabs, which all have fewer than five, or more
than five, teeth in this region. In addition, Carcinus maenas exhibits three
rounded lobes or bumps between the eyes (Washington Department ofFish and
Wildlife 2001a; see Figure 2). Green crabs may resemble juvenile Dungeness
crabs (Cancer magister) in shape; again, the primary way of distinguishing the
two is by spine count, since the juvenile Dungeness will have ten smaller spines
on each side ofthe carapace (Behrens Yamada, unpublished manuscript). The
native crab most confused with the green crab in Washington State is the helmet
crab, Telmessus cheiragonus. Although helmet crabs are frequently green, it
12

Figure 2. Adult European green crab (Carcinus maenas). Note the five
identifying spines on either side of the carapace, as well as the three lobes
between the eyes. (Photo by Liz Carr, Washington Department of Fish
and Wildlife)

13

should be noted that they have six, not five, spines on either side ofthe eyes; they
also possess bristly antennae and sport a body covered with stiff hairs
(Washington Department ofFish and Wildlife 2001a).

When measuring the size of a crab, the width of the carapace is typically
noted. A typical adult green crab has a carapace width of2.5 inches (64 mm), but
crabs as large as 4 inches (about 100 mm) have been found in their native range in
Europe. Here in Washington, captured green crabs have measured from 0.74
inches (19 mm) to 3.5 inches (90 mm) (Washington Department ofFish and
Wildlife 2001a). In a molt increment study done on the green crab in Oregon,
Behrens Yamada et al. (2000) report that green crabs at that location have fairly
high growth rates. They also postulate that, unfortunately, green crabs grow
larger in Oregon than in places like Maine or the North Sea, and that this may be
due to more favorable temperatures on the U.S. west coast.

The sexes may be distinguished outwardly in two ways. Unless immature
(smaller than 15 mm), the abdomen of males is more triangular in shape, whereas
the female green crab's abdomen is broader and rounder. Additionally, green
crabs larger than 30 mm react differently upon being picked up. Male green crabs
typically stretch out their claws and legs, where females usually fold their
appendages in closer to the body, a behavior that has been called the eggprotection reflex (Behrens Yamada, unpublished manuscript).

14

Reproduction and life cycle
Male green crabs molt more often and grow larger than females; they
typically mate with females smaller than themselves. In the North Sea and Maine,
mating primarily occurs from June (North Sea) or July (Maine) until October.
Most European green crabs extrude eggs in the spring (Washington Department of
Fish and Wildlife 2001a). Green crabs are quite prolific; females spawn up to
185,000 eggs at a time under favorable conditions (Cohen and Carlton 1995).

The new larvae aggregate in surface waters during the ebb tide at night,
when current velocities are at their highest. After a two-week period of growth
and development in the open sea, individuals in the crab's last larval stage
aggregate at night in surface waters during flood tides. This last stage (megalops)
then molts and settles out as a juvenile crab in upper intertidal zones (Washington
Department ofFish and Wildlife 2001a).

Green crabs reach maturity within two to three years, and may breed up to
three times per year. As green crabs age, they increasingly move from the
intertidal to the subtidal zones. Eventually, the oldest crabs live more or less
permanently in subtidal areas. The European green crab's minimum generation
time is three years, and the maximum life span, at least in native ranges, is five
years (Behrens Yamada, unpublished manuscript; Washington Department ofFish
and Wildlife 2001a).

15

THE GREEN CRAB PROBLEM

Deleterious ecological effects of green crabs
According to both field observations and laboratory experiments, Carcinus

maenas eats a vast array of organisms from at least 104 families and 158 genera,
in 5 plant and protist and 14 animal phyla (Cohen and Carlton 1995). Prey
includes clams, oysters, snails, other crabs, polychaetes, isopods, barnacles and
algae. In its native range, the green crab has a great impact upon populations of
mussels, dogwhelks, and cockles (Washington Department ofFish and Wildlife
2001a). In a study done in Nova Scotia, Canada, Singh (1991) indicates that the
crabs' diet in the intertidal zone of Crow Cove, Bay ofFundy, consists of
molluscs (especially bivalves and periwinkles) and crustaceans (especially
barnacles). At that location, as elsewhere, green crab dietary habits vary. This
may depend on the frequency and amount of prey available (Singh 1991). Not
only does the green crab have a great capacity for devouring diverse prey, but
other species living in marine environments may have to compete with the green
crab for food. These competitors may include native fish and birds (University of
Washington 1999-2001), as well as other crabs.

Since the arrival of green crabs in California, native shore crab populations
there have dropped significantly (Washington Department ofFish and Wildlife
2001a). Grosholz (1997) has shown that the yellow shore crab, also called the
hairy Oregon shore crab (Hemigrapsus oregonensis), exhibited a "significant
16

tenfold decrease in abundance" in Bodega Harbor from 1994-96. The declines
show a significant negative association with the increasing abundances of green
crabs. This should, unfortunately, come as no surprise. The Dungeness crab
(Cancer magister) and the yellow shore crab, both native residents ofthe Pacific
Northwest, may be consumed at up to the green crab's own size (Cohen et al.
1995; Grosholz and Ruiz 1995, as cited by Cohen and Carlton 1995). Predation,
however, is certainly not the only, or even main, reason for native crab population
declines. In the laboratory, Jensen et al. (2000) and McDonald et al. (2001)
performed experiments in which they forced green crabs to compete with
Dungeness and yellow shore crabs of similar size for both food and shelter.
Although yellow shore crabs were able to outcompete green crabs for shelter,
green crabs did indeed outcompete Dungeness crabs in this arena. And when it
came to food, green crabs were consistently able to outcompete both of the other
species, reaching and devouring the food sources first. Behrens Yamada
(unpublished manuscript) suggests that, due to more complex factors in the field,
these results should be interpreted carefully. However, she notes that these
laboratory experiments may serve as indications of" ... where the green crab fits
into the dominance hierarchy of the native crab guild" (Behrens Yamada,
unpublished manuscript). Green crabs have also been observed to kill the native
red rock crab, Cancer productus (Wiegardt, personal communication), although
Hunt and Yamada's (2001) laboratory studies report that red rock crabs are
generally more aggressive and will prey upon green crabs of smaller, and

17

occasionally equal, size. Hunt (2000) supports this last statement by observing
that there is a scarcity of green crabs found in abundant C. productus territory.

Native clam populations have also dropped significantly since green crabs
arrived in the State of California. For instance, studies have shown a significant
reduction in populations of native small clams, Nutricola (=Transennella) spp., in
habitats such as Bodega Bay, California (Cohen and Carlton 1995). Grosholz
(1997) reports that two species of Nutricola exhibited tenfold decreases in
abundance there from 1994-96; the declines show a significant negative
association with the increasing abundances of green crabs. In a study done at one
shellfish operation in Tomales Bay, California, the Manila clam (Tapes
philippinarum) harvest showed a 40% drop after the arrival of green crabs
(Biocontrol News and Information 1999; Grosholz and Olin 2000). Though the
Manila clam is a long-established exotic species itself, its hardiness apparently
does not make it immune to the dietary advances of the European green crab.
Additionally, Lafferty and Kuris (1996) believe that the green crab is likely to
cause major destruction to several Macoma clam and marsh mussel populations
(among others) in the future.

The green crab serves as interim host to the acanthocephalan worm
Profilicollis botulus, an endoparasite of shorebirds (Liat and Pike 1980), thus
posing yet another potential impact on ecosystems in Washington. For example,
the common eider (eider duck), Somateria mollissima (native to Scotland, North
18

America, and Asia) acquires Profilicollis botu/us by eating infected green crabs
(Rayski and Garden 1961, as cited by Thompson 1985; Rogers, personal
communication). In a study done on the transmission dynamics of Profilicollis
botulus, Thompson (1985) reports that the parasite's eggs are passed into the
external environment through the common eider's feces. These eggs, in tum,
infect green crabs, which then host the parasite's long-lived infective stage, called
a cystacanth. Upon eating a green crab, the common eider also ingests the
cystacanths, and the cycle repeats itself. Though common eiders would need to
ingest larger crabs and eat them more frequently in order to seriously threaten the
common eider population, Thompson (1985) states that this is a real possibility,
depending on the availability of other prey for the ducks, and also states that
" ... this may be one of the mechanisms by which an epidemic is produced"
(Thompson, 1985). In British Columbia, the Canadian province immediately to
the north of Washington State, Ching (1989) has found that Profilicollis botulus
parasitizes diving ducks. In that region, the native shore crab Hemigrapsus
oregonensis acts as interim host toP. botulus. With regard to the European green
crab, P. botulus has been found in these crabs not only in Scotland, but also in
Russia and on the eastern shores ofNorth America (Behrens Yamada,
unpublished manuscript). The potential for Profilicollis botulus to enter and
disrupt environmental systems in Washington State via the green crab should be
taken as a serious threat.

19

Green crabs are capable of learning and are able to improve their preyhandling skills while foraging. They are also not only quicker, but are able to
open shells in more ways, than other crabs (Washington Department ofFish and
Wildlife 2001a). The rear legs of the green crab are adapted for running across
mud, " ... something it does with a certain amount of elegance and at relative
lightning speeds," according to Rogers (2001a). Lee Wiegardt, a longtime oyster
grower in Nahcotta, Washington, reports that he has even observed green crabs
standing on their hind legs, presumably for increasing their visibility (Wiegardt,
personal communication). He has also observed that, after molting, green crabs
develop a hard shell much faster than many other crabs, a factor that would make
them less vulnerable to predators. These and other traits have earned Carcinus
maenas the title of"the working-man's crab" from Mr. Wiegardt. Though not a
large crab, pound for pound, green crabs can outcompete and outmaneuver other
crabs with ease. It is easy to see that they may constitute a significant threat to
other organisms in their environment, and have the potential to easily disturb
balances of existing ecosystems.

Deleterious economic effects of green crabs
It appears that aquaculture in Australia has not yet experienced significant

impacts from the region's green crab invasion, but since the arrival of the green
crab in Tasmania around 1993 (Proctor and Thresher 1997), worries have started
to surface that appear similar to worries found on the U.S. west coast. Some
research has been done; for instance, Walton (1997b) has done a preliminary
20

evaluation of potential Carcinus maenas impacts upon the fishery for Katelysia

scalarina, the native Tasmanian clam. He suggests that green crabs may indeed
have a very large impact upon the abundance and distribution of K. scalarina, and
thus upon the fishery.

In Canada, discussion about potentially negative economic effects of a
green crab invasion has ensued in British Columbia, Washington's neighbor to the
north. The shellfish aquaculture industry in British Columbia is currently based
on three species: the Pacific oyster (Crassostrea gigas), Manila (Japanese
littleneck) clam (Tapes philippinarum), and the Japanese weathervane scallop

(Patinopecten yessoensis). Cultures of the blue mussel (Mytilus edulis),
Mediterranean mussel (Mytilus galloprovincialis), geoduck (Panopea abrupta),
and Pinto abalone (Haliotis kamtschatkana) are either being developed or are in
early stages of production (British Columbia Shellfish Growers Association
2001). According to the University ofVictoria (2000), the latter four species have
great potential for increased production value. According to 1998 figures, the
annual wholesale value of the shellfish industry in British Columbia is about $15
milli~n,

but it is estimated to be capable of producing $100 million per year. This

could have positive implications for depressed coastal communities. However, a
2000 workshop report states that the threat of exotic species-the only one it
names specifically is Carcinus maenas-may be of equal or even greater
importance than the threat of global climate change to this Canadian industry
either now or in the future (University of Victoria 2000).
21

Carcinus maenas is thought by many to be responsible for the destruction
in the 1950s of the soft-shelled clam fisheries in New England and Canada
(Cohen et al. 1995). In 1938, New England fishermen brought in 14.5 million
pounds of the soft-shelled clam Mya arenaria, a record high. By 1959, that
number had dropped to an abysmal 2.3 million pounds, hurting the region and
thousands of people economically. During these same years, the range ofthe
green crab expanded, and many attribute the decrease in clam catches, at least in
part, to this invasion (Welch 1968, as cited by Behrens Yamada, unpublished
manuscript). The population explosion and range expansion of the green crab can
be correlated with the rise in ocean temperatures around the tum of the twentieth
century (Rogers 2001a). If this trend holds true on the U.S. west coast, the green
crab problem can only be exacerbated by predicted climate changes.

Additional impacts by the green crab have been felt on North America's
east coast. The quahog (Mercenaria mercenaria), an edible clam also known as
the hard-shelled or round clam, has decreased in numbers, as has the blue crab
(Callinectes sapidus). The green crab is thought to be responsible for both of
these declines (Rogers 2001a). Bay scallops (Argopecten irradians) are also a
favorite food of green crabs, and residents along the U.S. east coast in Martha's
Vineyard, Massachusetts, have actually instituted bounty programs on green crabs
in order to try to decrease their scallop losses (Fincham 1996; Walton 1997a).

22

Because the green crab has not been a resident on the U.S. west coast for
long, there are fewer documented examples of its destructive impacts on the
aquaculture industry. But some scientists like Lafferty and Kuris (1996) believe
that the green crab is likely to devastate subtidal and intertidal beds of species
such as the soft-shelled clam (Mya arenaria) and the Manila (Japanese littleneck)
clam (Tapesjaponica) in places such as San Francisco. Scientists can only guess
the impacts Carcinus maenas could have in Washington, based in large part upon
results of experimentation with green crabs and other organisms in the laboratory.
These studies provoke concerns about the green crab's potential economic
impacts. For instance, laboratory studies have confirmed that the green crab preys
upon organisms such as the California mussel (Mytilus californianus),
Mediterranean mussel (M galloprovincialis), and blue mussel (M edulis), which
are found in large numbers along the U.S. west coast (Cohen and Carlton 1995;
Sheldon 1998). Additionally, studies done outside the laboratory have already
indicated downward trends in harvest rates; recall the study done in Tomales Bay,
California, which showed a 40% drop in one operation's Manila clam harvest
after green crabs arrived in that area (Biocontrol News and Information 1999;
Grosholz and Olin 2000). Shellfish appear to be immune to green crab predation
when they reach a certain size-60 mm for oysters and 45 mm for mussels-but it
is the smaller-sized shellfish and seed stocks that will suffer. The Washington
Department ofFish and Wildlife (2001a) states that nearly three dozen mussels
under 45 mm in length may be eaten daily by a green crab. Wilhelm (2000)
alleges that one green crab can eat more than 40 young shellfish per day.
23

Statements such as this evoke alarming scenarios for the future of commercially
important marine organisms.

Estimates ofthe value ofthe Washington State shellfish industry (which
includes both the coast and Puget Sound) vary, but it is worth at least an annual
$40 million. Some estimates place it as high as $100 million annually (Rogers
2001a). People for Puget Sound (1996) reports a figure of$65-$70 million total
commercial harvest in Washington for the year 1993. The British Columbia
Shellfish Growers Association (2001) states that Washington's shellfish culture
industry is estimated at greater than $60 million annually; Wilhelm (2000) cites
the Washington shellfish industry as currently generating $73 million in revenue
per year, and employing approximately 2,000 people. One analysis estimates that
eachjob in the oyster industry supports 1.13 additional jobs elsewhere in the state
economy (People for Puget Sound 1996). If we apply this figure to the shellfish
growers in Washington, approximately 4,260 jobs are currently related to the
shellfish industry in this state. Many of these jobs are a significant employment
base and show long-term, sustainable economic growth for rural and distressed
communities. The oyster industry in Puget Sound is one of the two most
significant sources of commercial oysters in the nation, and overall, Washington
State is " ... the largest producer of cultured clams and one of the top two
producers of cultured mussels in the western United States" (People for Puget
Sound 1996).

24

The Washington Department ofFish and Wildlife (2001a) states that it
believes the green crab will pose significant threats to the state's clam, oyster, ·and
mussel industries if it ends up becoming established in Washington waters. As is
the case in British Columbia, Washington State shellfish growers are already
worriedly discussing potential green crab impacts amongst themselves. Lee
Wiegardt, an oyster grower with 11,000 feet of shoreline in western Washington
State, reports that so far he does not know of any local oyster growers that have
suffered problems or damage due to green crab predation. However, the number
of green crabs that have been discovered in Washington is still small, and oyster
growers are anxious about larger numbers having potential impacts on their
businesses. Wiegardt notes that green crabs appear to go after Manila clams first
("the crabs would rather eat caviar than peanutbutter"), but he also worries about
what could happen if clam populations decrease and the green crab expands its
tastes (Wiegardt, personal communication).

Puget Sound, in particular, is a very productive bivalve shellfish-growing
area. The Puget Sound Water Quality Action Team (2000) reports that the Puget
Sound shellfish industry produced 50 million pounds live weight of bivalve
shellfish (clams, oysters, and others) in 1998. This translates to a wholesale value
of$50 million for that year, with 140,000 acres of commercial shellfish acreage in
production. People for Puget Sound (1996) estimates that Puget Sound shellfish
growers brought in about half of the $65-$70 million harvested statewide in 1993.

25

Annual shellfish production in Puget Sound has been increasing in past years, and
more than doubled from the years 1979 to 1993.

As previously mentioned, green crabs have not yet been spotted in Puget
Sound. This is fortunate because, among other things, the last 20 years have seen
increased restrictions on shellfish harvesting due to pollution and high levels of
fecal coliform (People for Puget Sound 1996). Because of the concentration of
shellfisheries in the Puget Sound area, it is economically essential that the State of
Washington not only maintain its current coastal trapping programs in order to
inhibit a green crab spread, but it is also essential to continue the monitoring
efforts that are presently taking place in the Sound itself. If green crabs are
detected early (and pursued), the aquaculture industry will have a much greater
chance of maintaining their current catches, an already somewhat difficult task
due to water quality issues. Additionally, in the event of an influx of green crabs,
early detection allows shellfish growers to have more time to mount defenses
against the green crab. These tactics can include surrounding shellfish beds with
more appropriate fencing, using small-meshed nets, covers or bags, or adjusting
the time of planting seed stocks, a viable option if settlement rates of green crabs
are known (Behrens Yamada, unpublished manuscript). The fact that the
commercial shellfish industry deems these issues important should be one of the
deciding factors in whether the Washington State legislature decides to keep
current funding in place, and whether they decide to increase such funding.

26

Besides the shellfish industry, the green crab could have a major impact on
both the Dungeness crab (Cancer magister) and flatfish fisheries, such as that for
the English sole (Pleuronectes vetulus). These two Pacific Northwest fisheries are
collectively valued at $130-$135 million coast wide, roughly split between
Oregon and Washington (Rogers 2001a; Rogers 2001b). The Dungeness crab is
a commercially valuable species in the State of Washington. As a popular catch
and preferred seafood dish, the State of Washington works to protect Dungeness
crabs from over-exploitation by prohibiting all but male crabs larger than 6.5
inches (17 em) from being taken (Sheldon 1998). As mentioned earlier, green
crabs may eat Dungeness crabs at up to their own size, and thus have the potential
to wipe out vast numbers of younger Dungeness crabs before they even have the
chance to reach a commercially viable threshold.

Additional impacts upon biodiversity in Washington State
I have found little discussion on how a green crab invasion might affect
non-commercial species in the Pacific Northwest, especially those that are species
of concern (a term I use here in a general sense). In its July 1999 publication
Priority Habitats and Species List, the Washington Department ofFish and
Wildlife provides an outline of species that the state considers to be of priority f<?r
management and preservation. Included in this list are several gastropods and
bivalves, and two crustaceans. Since these priority species are rarely included in
current discussion or literature addressing potential green crab outbreaks, I have
included a discussion of them here.
27

A list of Washington species of concern that are potentially vulnerable to a
green crab invasion may be found in Table 1. These listings have been taken
from the Priority Habitats and Species List (Washington Department ofFish and
Wildlife 1999a). I have included only those species that are potential food
sources for the green crab. I decided upon this particular list after reviewing the
dietary intakes and habits of green crabs, both in the United States and elsewhere.

The priority species found in Table 1 include state listed species
(endangered, threatened, or sensitive), state candidate species (to be reviewed by
the Washington Department ofFish and Wildlife for possible listing), species that
occur in vulnerable aggregations (susceptible to significant population declines),
and species of recreational, commercial, and/or tribal importance that are
vulnerable (Washington Department ofFish and Wildlife 1999a). Each category
is numbered for easy referencing in the table.

The first species on the list, Newcomb's littorine snail (A/gamorda

subrotundata, also classified as Algamorda newcombiana and Littorina
subrotundata), is a Washington State Candidate species (to be reviewed by
Washington Department ofFish and Wildlife for possible listing as Endangered,
Threatened, or Sensitive), and a Federal Species of Concern as well (Washington
Department ofFish and Wildlife 2000a). As can be seen in Table 1, it
congregates in vulnerable aggregations that are susceptible to significant
28

N

1..0

Priority Species Criteria

Priority Areas

Common Name

Scientific Name

Newcomb's littorine snail

Algamorda subrotundata

1, 2

Any occurrence*

Pinto (Northern) abalone

Haliotis kamtschatkana

1, 2, 3

Any occurrence

Geoduck clam

Panopea abrupta

2, 3

Regular and regular large concentrations**

Butter clam

Saxidomus giganteus

2, 3

Regular and regular large concentrations

Littleneck clam

Protothaca staminea

2, 3

Regular and regular large concentrations

Manila clam

Tapes philippinarum

2, 3

Regular and regular large concentrations

Olympia oyster

Ostrea lurida

1, 2, 3

Any occurrence, regular and regular large concentrations

Pacific oyster

Crassostrea gigas

2, 3

Regular and regular large concentrations

Razor clam

Siliqua patula

2, 3

Regular and regular large concentrations

Dungeness crab

Cancer magister

2, 3

Breeding areas, regular and regular large concentrations

1 = State Listed species (Endangered, Threatened, or Sensitive) or State Candidate species (to be reviewed for possible listing)
2 = Vulnerable aggregations (susceptible to significant population declines)
3 = Species of recreational, commercial, and/or tribal importance that are vulnerable
*
Any occurrence means that either the species is rare, or its limiting habitats are not known.
** Regular concentrations are defmed as areas that are commonly or traditionally used by a group of animals on a seasonal or year-round basis. Regular
large concentrations are defmed as areas that are commonly or traditionally used by significantly large aggregations of animals, relative to what is expected
for a particular species or geographic area.

Table 1. Washington priority species (Washington Department ofFish and Wildlife 1999a) potentially vulnerable to the European green crab.

population declines. This small marine snail, which sports a thin, conical shell, is
typically found clinging to rocky shores in the upper intertidal zone. Its greatest
threats are habitat loss and introduced species such as the green crab (Pacific
Biodiversity Institute 2001 ). Thought to live on pickleweed (Salicornia virginica)
in Willapa Bay's native saltmarsh (Washington Department ofFish and Wildlife
1995), Newcomb's littorine snail may already be experiencing habitat loss as a
result of Spartina alterniflora crowding out native vegetation such as pickleweed.
A larger incoming population of green crabs may be all it takes to push this snail
population to the point of no return.

The Pinto (Northern) abalone, occasionally called the Japanese abalone

(Haliotis kamtschatkana), is a Washington State Candidate species as well. It,
too, falls into the "vulnerable aggregations" category found in the Priority

Habitats and Species List. This marine mollusc is the smallest of abalones,
reaching a maximum length of 6-7 inches (18 em). These abalones are usually
found clinging to rocks in kelp beds between the low intertidal zone and 18 m
depth. Mortality rates of larvae and young adults are extremely high, and their
thin shells are easily damaged, leaving them vulnerable to predators. Commercial
overharvesting from 197 5 to 1990 drastically reduced Pinto abalone populations.
Since then, harvesting of the species has been banned over much of its range,
which runs from California to Alaska. Recreational harvesting within
Washington was closed in 1994, but along with habitat loss, poaching continues
to pose a serious threat to recovering populations (Pacific Biodiversity Institute
30

2001; Sheldon 1998). The additional threat of an invasive species could easily
add to the Pinto abalone's dismal outlook.

Geoduck clams (Panopea abrupta or Panope generosa), though they may
seem invulnerable because of their large size, are listed in the "vulnerable
aggregations" category and are thus susceptible to significant population declines,
as are all clams and oysters listed in Table 1. Living up to almost 150 years, the
geoduck has been threatened by overharvesting. At the age of 6-7 years, this clam
is ofharvestable size (Sheldon 1998). Regulations are enforced against the taking
of younger geoducks, but the youngest geoducks are those to which the green crab
poses a threat.

Three hard-shelled clams have also made the priority species list. The
butter clam (Saxidomus giganteus), also known as the smooth Washington clam,
is the mainstay ofthe clam industry. Regulations are in place to keep smaller
clams from being taken; this allows the populations to sustain themselves
(Sheldon 1998). However, it is these same smaller-sized clams that are most at
risk of being preyed upon by the European green crab.

The littleneck clam (Protothaca staminea) goes by several different
common names, including native littleneck, rock cockle, common Pacific
littleneck, and steamer clam. The minimum size harvestable by law tends to be
around 1.5 inches, or 38 mm (Sheldon 1998). Adding to its troubles of
31

displacement by the exotic Manila (Japanese littleneck) clam, this native clam is
also a potential food source for the green crab.

The Japanese littleneck (Tapes philippinarum, Tapesjaponica) clam's
most frequently used conunon name is the Manila clam, although it too is
sometimes known as the steamer clam (see above, Protothaca staminea). This
intentionally-introduced clam from the west Pacific Ocean has become common
in waters of the Pacific Northwest, and has frequently displaced the native
littleneck clam (Sheldon 1998). Manila clams are now listed as being capable of
having vulnerable aggregations susceptible to significant population declines.
Sheldon (1998) reports that huge numbers can be killed by cold winters. It has
been shown that green crabs eat Manila clams in both the field and the laboratory
(Cohen et al. 1995; Grosholz and Ruiz 1995, as cited by Cohen and Carlton 1995;
Grosholz and Olin 2000). Wiegardt (personal communication) also reports seeing
green crabs go after Manila clams as a favorite food source. This could obviously
spell trouble for the large Manila clam industry in Washington and British
Columbia. The Washington Department ofFish and Wildlife (2001a) states that
the green crab will pose a "significant threat" to the state's clam and oystergrowing industries if it ends up becoming established in Washington waters; this
is not only an important issue economically, but one can see that it also poses a
threat to the balance of existing ecosystems in the state.

32

The Olympia oyster, Ostrea lurida (=conchaphila), is another species that
is listed as a State Candidate species in Washington, in addition, of course, to
falling into the "vulnerable aggregations" category. This shellfish, Washington
State's only native oyster, has been displaced in large part by the non-native and
larger Pacific oyster (Crassostrea gigas). Once abundant along the U.S. west
coast, it has now disappeared from much of its original range (Sheldon 1998).
Overharvesting significantly depleted stocks in Willapa Bay and Puget Sound by
the 1870s. In addition, the Olympia oyster is sensitive to pollutants, particularly
pulp and paper mill effluent, and these pollutants played another large part in its
decline, particularly before the 1950s when the industry was unregulated. When
oystermen began to enhance their ailing native stocks by bringing in the Pacific
oyster, the Olympia oyster experienced further declines due to competition.
Along with their Pacific oyster hosts, invasive species such as the Japanese oyster
drill (Ocenebrajaponica) and a parasitic flatworm (Mytilicola orienta/is) were
introduced (Pacific Biodiversity Institute 2001 ). Although reintroduction efforts
are currently underway, the threat of another non-native species needs to be
seriously addressed if we want to ensure that these restoration efforts will be
successful and guarantee the survival of the Olympia oyster in Washington State.

Ironically, the Pacific oyster (Crassostrea gigas) has made the priority
species list, in spite of the fact that it is originally an introduced species itself, as it
is susceptible to significant population declines. Now the greatest contributor to
the oyster industry, the Pacific oyster (also called the Japanese oyster) has been a

33

victim of other introduced species such as the Atlantic oyster drill (Ursosalpinx

cinerea) (Sheldon 1998).

Razor clams (Siliqua patula) are occasionally used effectively as bait
when trapping green crabs (Washington Department ofFish and Wildlife 19982000b), so we can guess that green crabs at least enjoy the taste. Razor clams,·
once again, are a clam listed in the "vulnerable aggregations" category, and are
protected from overharvesting by regulations prohibiting the taking of any clams
under 4.5 inches, or 11 em (Sheldon 1998). It should be noted that green crabs
and razor clams may not always share the same habitat (personal observation), so
it is possible the crabs might not be as much of a threat to razor clams as they are
to the other species listed in Table 1.

Finally, the Dungeness crab, Cancer magister, has found its way onto the
priority species list, being classified in the "vulnerable aggregations" category, as
well as being a "species of recreational, commercial, and/or tribal importance that
(is) vulnerable" (Washington Department ofFish and Wildlife 1999a). It is
apparently for these reasons that the State of Washington regulates against the
taking of any Dungeness crabs that are not male and at least 6.5 inches in size. As
previously mentioned, green crabs can and do consume Dungeness at up to their
own size, according to laboratory studies (Cohen et al. 1995; Grosholz and Ruiz
1995, as cited by Cohen and Carlton 1995). Since Dungeness crabs spend part of
their early life in the intertidal zone, they may be at risk of predation by green

34

crabs during that time (Washington Department ofFish and Wildlife 200la). But
this is not the only threat that Carcinus maenas poses to Cancer magister. Green
crabs compete intensely with other crabs for food and shelter (Behrens Yamada,
unpublished manuscript). Recall the McDonald et al. (2001) laboratory trials,
where green crabs were matched with similarly-sized Dungeness crabs and forced
to compete. Green crabs consistently beat Dungeness crabs not only to food
sources, but they also won the race to sources of shelter.

As can be seen, a green crab influx could pose a serious threat to
biodiversity in Washington State. When deciding whether or not to continue or
increase monitoring, prevention, and control activities, this potential threat should
be weighed heavily. Declines in sensitive populations are difficult and expensive
to reverse. And if any of these priority species should disappear, they could easily
be gone for good.

35

PREVENTING, DETECTING, AND CONTROLLING GREEN CRABS

Introduction
Washington State's response to the green crab invasion centers on both
management and control of existing crabs, and avoiding new introductions. In
Puget Sound and the Strait of Juan de Fuca, no green crabs have yet been found,
and extensive monitoring is currently being done in order to detect any future
problems. Meanwhile, in Willapa Bay and Grays Harbor, measures have been
undertaken to reduce existing green crab populations. Whether the green crab
population in those areas remains at current levels, decreases, or rises, it is
important to look at different methods of green crab control (as well as detection
and prevention) in various parts of the United States and other countries for
possible adoption by Washington. Analyzing different methods of control will
help us utilize feasible, pertinent methods that are most applicable toward
European green crab control in our state. This section discusses what we already
know and what further research needs to be done, and makes an attempt to
determine if Washington State is making the best use of its sometimes scarce
monetary resources in the war against Carcinus maenas.

Prevention measures
According to scientists and many policy makers, the best green crab plan
focuses on avoiding introduction in the first place. It is therefore critical to
institute and maintain prevention measures in Washington State. These measures
36

can help to keep the green crab from spreading out ofWillapa Bay and Grays
Harbor. It is hoped that the green crab will never enter Puget Sound or the Strait
of Juan de Fuca. However, those areas are at high risk, not only because of the
coastal infestations, but also because green crabs have been found near Totino,
near Victoria, and in Barkley Sound (Behrens Yamada, unpublished manuscript).
All these locations are on Vancouver Island, British Columbia, immediately to the
north ofPuget Sound.

Several important actions have recently been implemented in Washington
State that are designed to prevent green crabs (as well as other invasive species)
from spreading further into the state's waters, including Puget Sound and the
Strait of Juan de Fuca. The first is the establishment of restrictions on the import
and transfer of shellfish by the Washington Department ofFish and Wildlife
(Rogers 2001a). This regulation prohibits the transfer of shells, shellfish, and
aquaculture equipment from Willapa Bay or Grays Harbor to other Washington
waters, unless permission is granted from WDFW (Washington Department of
Fish and Wildlife 2001a).

The State of Washington has also enacted an emergency regulation (WAC
232-12-01701) that labels the European green crab a deleterious exotic species
and prohibits persons from transporting and possessing any live green crabs
without a special permit. Under no circumstances can green crabs be released to
local marine waters (Washington Department ofFish and Wildlife 2001a).
37

Additional restrictions have been placed on imports from out-of-state.
These include " ... requiring one-hour chlorine dips for shellfish seed and
broodstock from European green crab infested areas" (Washington Department of
Fish and Wildlife 2001a). And as WAC 232-12-01701 states, "Live European
green crabs may not be imported into Washington without first obtaining written
permission from the director ofWDFW'' (Washington Department ofFish and
Wildlife 2001a).

Finally, groundbreaking legislation was passed in the spring of2000 that
regulates the discharge of ballast water in the state, the Ballast Water
Management Act (RCW 77.120). On September 22,2000, Washington State
began enforcing its first new ballast water rule. Among other things, coastal
cargo vessels must now exchange ballast water at least 50 miles offshore and
report the exchange. Vessels must file a ballast water management report at least
24 hours prior to discharging their ballast in Washington waters, the report being
submitted to the Washington Department ofFish and Wildlife. After July 1,
2002, discharge ofballast water into Washington waters " .. .is prohibited unless it
has been adequately exchanged or treated to meet standards to be set by the
Washington Department ofFish and Wildlife" (Washington Department ofFish
and Wildlife 2000b; Washington State Aquatic Nuisance Species Committee
1998). These measures greatly reduce the risk of green crab larvae hitchhiking
into Washington in the hulls of ships and, of course, aid in preventing
38

introductions of other exotic species. Washington is considered by some to be
one of the most progressive states in trying to stop the spread of invasive species;
the new ballast water management law is a good example of this. The law is only
the second of its kind-California did it first-passed in the United States
(Wilhelm 2000).

Early detection (monitoring)
Rogers (2001a) states that, once an area has been infested, the "only
known method that holds promise" is early detection and subsequent removal of
as many individuals as possible. He feels that this method is still a viable option
for the coasts of Washington State, British Columbia, and Alaska.

In 1999, a large-scale green crab monitoring program was established,
with the Washington Department ofFish and Wildlife as the coordinating agency,
in the Puget Sound region. This monitoring program includes not only Puget
Sound itself, but also the Strait of Juan de Fuca and the San Juan Islands
(Washington Department ofFish and Wildlife 2001a). The headquarters for these
coordinated activities are WDFW's Point Whitney Shellfish Laboratory in
Brinnon, Washington, on the northwestern shores of Hood Canal. This program
is detective in nature, and is also aimed at keeping green crabs from spreading
into the Puget Sound region from Grays Harbor, Willapa Bay, British Columbia,
and points unknown. The Puget Sound monitoring program is extensive. In the
three years from 1999 to the present (2001), roughly 200 sites have been
39

established at locations that are considered high-risk (Rogers 2001a; Sato,
personal communication; Washington Department ofFish and Wildlife 1999e;
Washington Department ofFish and Wildlife 2001a). Figure 3 shows locations
where monitoring has been done in Puget Sound, the San Juan Islands, and along
the Strait of Juan de Fuca. The vast majority of these sites are still in existence.

Baited crayfish traps are set out at various monitoring points around the
Puget Sound region, and are periodically checked for the presence of green crabs
(Washington Department ofFish and Wildlife 2001a). Out ofthe approximately
200 sites established since the program's inception, 51 have been monitored
exclusively by the Washington Department ofFish and Wildlife (Sato, personal
communication; Washington Department ofFish and Wildlife 1999e; Washington
Department ofFish and Wildlife 2001a). The major emphasis is on checking the
traps from April to September, the months when green crabs are most likely to be
found (Rogers, personal communication).

Adopt-a-Beach, a now defunct non-profit organization whose goals
included maintaining healthy beaches in the region, was originally responsible for
checking approximately 35-40 of the trapping sites, using volunteer members.
These volunteers were trained by the Washington Department ofFish and
Wildlife to set crayfish traps and check them for green crabs. Fortunately, when
Adopt-a-Beach went under, most of these volunteers transferred their loyalties to

40

~
~

!r.Green Crab Monitoring Groups

*

WDFW

•

Volunteer

•

MSC/Aquariums

•

Shellfish Growers

•

Tribes

.a.

Educational Institutions

•

Other Govt. Agencies

"'

..

:io<~~ ~
~

~

.,.'¥·~;~

>oi

...

~

Figure 3. Representative monitoring sites for the European green crab in the Puget Sound
region of Washington State, 1999-2001 (not all sites in heavily monitored areas included).
MSC =Marine Science Center. (Map modified from Washington Department of Fish and
Wildlife 1999e)

41

the Puget Sound Restoration Fund, which took over the effort. All site-checking
activities formerly run by Adopt-a-Beach were thus largely kept intact. The
Washington Department ofFish and Wildlife contracts with Puget Sound
Restoration Fund on this effort, paying $6,000 a season (March- September) to a
part-time employee at the Restoration Fund. The person in the part-time position
is responsible for coordinating the checking of traps that Puget Sound Restoration
Fund has now assumed responsibility for (Rogers, personal communication).
Currently, approximately 30 of out a possible 60 monitoring sites are being
checked by PSRF volunteers (Sato, personal communication).

The remainder of the approximately 200 total sites (about 110 over the last
three years) have been checked by other government entities besides WDFW
(county, state and federal), and individuals from local tribes, marine science
centers, and schools, as well as additional volunteers that have included a handful
of shellfish growers. All told, WDFW and other government employees have
been responsible for approximately 65 sites in the last three years, with about 135
sites--over 67% of the total-being monitored by volunteer groups and
individual volunteers (Sato, personal communication; Washington Department of
Fish and Wildlife 1999e; Washington Department ofFish and Wildlife 2001a).
The Washington Department ofFish and Wildlife in Brinnon coordinates these
activities. There is a specific position at WDFW delegated for this task, that of
the Puget Sound Monitoring Coordinator (Rogers, personal communication).

42

To date, no green crabs have been found in Puget Sound, the San Juan

.

Islands, or the Strait of Juan de Fuca, at least not on the Washington side. One
green crab has been found near Victoria, British Columbia, which is located on
the Strait of Juan de Fuca's northern shore (Rogers 2001b).

Though state funding for continuation of green crab monitoring and
control programs was previously in doubt, current funding levels will almost
certainly remain in place for the July 2001 -June 2003 time period (Jacobsen,
personal communication). It is commendable that the State of Washington is
taking such a proactive stance. Not only is Washington maintaining funding for
programs involving actual capture of existing crabs, but the state is also
continuing a program that searches for new ones. Economically, this is a good
choice, for common sense, as well as experience, tells us that it is least costly to
head off non-native species invasions at the pass.

Trapping
The physical-control method of trapping is cited by Rogers et al. (2000) as
the most environmentally sound and cost-effective option for the control of green
crabs. However, it appears that not all crabs enter traps, so additional methods of
control may sometimes need to be used (Rogers et al. 2000). Trapping has been
used on North America's east coast; success there has been varied (Cohen et al.
1995; Walton 1997a).

43

The major method of green crab control in Washington State has been the
use of traps. Success in trapping is measured in CPUEs, or catch per unit effort,
and is determined by taking the number of crabs caught and dividing this number
by the number of hours the traps were in place. The most effective, cost-efficient,
and easily deployed traps are modified crayfish traps, which are set in lower
intertidal areas around the perimeters of the bays (Rogers et al. 2000). These are
used rather extensively in the Willapa Bay and Grays Harbor areas, the only
places in Washington where the green crab has been found.

Pit-fall traps, which have a more permanent nature, are also used by
WDFW, primarily at their long-term monitoring sites. They are made by digging
a hole in the ground and dropping a 5-gallon bucket into the hole. Green crabs
then fall into the traps and cannot get out. Pit traps have also proved to be quite
effective in catching green crabs (Dumbauld, personal communication; Rogers et
al. 2000).

More males than females are trapped, at least in the two Washington bays.
This is probably partially due to two types of trapping bias. Male green crabs are
more aggressive, and may get into crayfish traps first and then keep the females
away. Also, males can potentially eat females and smaller crabs while in the
traps. Because crabs cannot climb out of pit traps, the use of pit traps largely
eliminates the first trapping bias, but cannot eliminate the second (Dumbauld,

44

personal communication). Brooding females also have a tendency to avoid traps
better than males (Sea Grant Oregon 2000).

Figure 4 shows the locations where green crab traps have been placed in
the Willapa Bay and Grays Harbor areas, and indicates which sites have seen the
capture of green crabs and which have not. The trapping program has been
maintained by Washington State Department ofFish and Wildlife biologists since
1998. Since then, a steady decline in the numbers of crabs caught has been noted
in both regions, as can be seen in Figure 5, which graphs the CPUE against years
1998 through 2000. However, it is uncertain how much of this is due to trapping
measures, and how much to lack of recruitment and other factors. Most likely, it
is a combination of variables (Rogers 2001a). An exception to the decline in
number of crabs caught has been in the current calendar year, 2001. As of June,
spring trapping results seemed to indicate the same number of green crabs being
caught as in the spring of2000 (Figlar-Barnes, personal communication).
Further discussion of Washington's trapping program is included in the section
"Population status," below.

Various types ofbait are usually placed in the traps, with varying degrees
of success. Fresh fish-such as mackerel-seems to work best, and is most often
used by the Department ofFish and Wildlife (Rogers et al. 2000). Other baits that
have been successful include whitefish, salmon, calamari, oysters, razor clams,

45

s

Pacific Ocean

- --

10

0

10

•

successful survey
(Green Crab Captured)

•

Surveys Completed
(No Green Crab)

20 Kilometers

Figure 4. Washington Department of Fish and Wildlife green crab survey effort,
Willapa Bay and Grays Harbor, Washington, 1998-2001. (Source: Washington
Department of Fish and Wildlife 2001b)

46

0.016
0.014
t:'C'
0

5

0.012

~

~

=.s::.
C1)
~ a. 0.01
c:: m
::s .:::
~ ~ 0.008
C1) C1)
a. a.
.s::. U) 0.006
I

o.C

u

- m 0.004
~
.j:>..
-..)

-

0.002
0
1998

~

~

- - - Willapa Bay

~

•

~\.._

-

•

.

1999

2000

Grays Harbor

Year

Figure 5. Catch per unit effort (CPUE) of European green crabs caught by the Washington Department of Fish and Wildlife in Willapa
Bay, Washington, 1998-2000, and in Grays Harbor, Washington, 1999-2000. Grays Harbor data from 1998 unavailable.
(Source of data: Washington Department of Fish and Wildlife 1998-2000a; Washington Department of Fish and Wildlife 1998-2000b)

mussels, and even cat food-which is the bait most often used in Puget Sound
monitoring efforts (Rogers, personal communication; Washington Department of
Fish and Wildlife 1998-2000a; Washington Department ofFish and Wildlife
1998-2000b).

Many local volunteers (usually property owners but also oyster growers,
high-school students and college students) have pitched in to help WDFW check
traps for the presence of green crabs (also see "Volunteer programs" section). The
2001 monitoring effort includes help from the Makah, Quileute, and Shoalwater
tribes, as well as the Columbia River Estuary Task Force (CREST). These efforts
will result in additional coastal surveillance (Washington Department ofFish and
Wildlife 2001a), and may help to keep green crab populations down via additional
trapping.

Although continued state funding for this program was in question earlier
this year (2001), it is now believed that current funding levels will remain in place
for the July 2001 -June 2003 time period (Jacobsen, personal communication).
This is good news for the Washington Department ofFish and Wildlife, which
has advocated that trapping efforts continue indefinitely or until no more green
crabs can be found (Rogers 2001a).

If a detection does occur in the Puget Sound region, where no crabs have
been found to date, the Department ofFish and Wildlife is prepared to launch an
48

intensive trapping effort to control or eliminate those green crabs as soon as
possible (Rogers 2001a).

Keeping crabs out of specific areas
Fencing is a physical control method that has been used in the fight against
the European green crab. It is used to exclude green crabs from certain areas,
thereby protecting shellfish and other organisms vulnerable to disturbance by the
green crab. The fences, nets, or other materials need to be such that even small
green crabs cannot crawl through them and into the shellfish areas. Fencing has
been used in New England and Canada, with varying levels of success (Behrens
Yamada, unpublished manuscript; Cohen et al. 1995). In Tomales Bay,
California, mesh enclosures seem to be working successfully in reducing
predation of green crabs on clam and oyster seeding operations (Lafferty and
Kuris 1996). Other tactics include placing small-meshed nets, covers, or bags
immediately over or around shellfish (Behrens Yamada, unpublished manuscript).

Use of carbaryl as a pesticide
Although potentially a rapid response to an exotic species invasion, the
use of pesticides to control green crabs has drawbacks, especially in terms of
harming other species in the areas treated. Poisoning has been used in both New
England and Canada, however, and, like fencing, it has met with different levels
of success (Cohen et al. 1995).

49

The Washington Department ofFish and Wildlife (2001a) has declared a
provisional stance on the use of chemical control at the present time. They report
that although chemical methods to control the green crab have been proposed,
basic research for implementation is lacking, and any chemical control would
have to be "carefully considered" before use. Carbaryl, currently used in selected
spots ofWillapa Bay for the control ofburrowing shrimp, which are known to
severely damage oyster populations (Aasen 1997; Campbell and Riener 1992), is
a possibility. If implemented, it would first be used in the form of poison bait,
initially in a trap, so that effectiveness and damage to other organisms could be
studied (Washington Department ofFish and Wildlife 1999d).

Carbaryl is a broad spectrum, synthetic pesticide that belongs to the family
of chemicals known as carbamates, which are esters of carbamic acid that inhibit
cholinesterase. It is a white crystalline solid that may be formulated as aqueous
dispersions, baits, wettable powders, pellets, granules, dusts, suspensions and
emulsifiable concentrate solutions (Meister 2000). Carbaryl is mixed with polar
organic solvents such as acetone and mixed cresols (Meister 2000), and is applied
by ground or aerial spraying methods, at least in the case ofburrowing shrimp
(Aasen 1997). According to manufacturers, protective clothing should be worn
when handling carbaryl, including rubber gloves, respirators, rubber boots
(depending on formulation), long-sleeved shirts or jackets, and long pants
(Meister 2000). Human health effects may be felt if workers handling carbaryl do
not wear protective clothing or are overexposed. Overexposure may cause blurred
50

vision, muscle tremors, difficulty breathing, abdominal cramps, vomiting,
diarrhea, weakness, unconsciousness and respiratory failure. Repeated incidents
of overexposure could cause severe cholinesterase inhibition, and workers
regularly exposed should have periodic checks of red blood cell cholinesterase
levels (Information Ventures, Inc. 1995).

Listed as being "toxic to animals of fish diet" and toxic to estuarine and
aquatic invertebrates, carbaryl is also extremely toxic to bees (Information
Ventures Inc. 1995; Meister 2000). It has been found to be more toxic to
crustaceans than to molluscs or fish (Campbell and Riener 1992), but is also
moderately toxic to fish and can build up (bioaccumulate) in fish tissue
(Information Ventures, Inc. 1995). The Pesticide Action Network (2000) lists this
pesticide as being "highly toxic" to both crustaceans and aquatic insects, and
"moderately toxic" to fishes, annelids, and zooplankton. Carbaryl is not as toxic
to mammals. Its oral LD50 for rats is listed as 246-283 mg/kg (Meister 2000).
Carbaryl has signal words of either "Caution" or "Warning" on the label,
depending on the formulation (Meister 2000), and this includes the words
"extremely toxic to aquatic and estuarine invertebrates" on the Sevin label,
carbaryl's most common trade name (personal observation).

Carbaryl is listed as a possible carcinogen by the U.S. EPA, which means
there is some evidence of cancer found in animals, but none as yet in human
populations (Dickey, personal communication; USEPA 1999). It is also a
51

suspected endocrine disrupter, according to the Preliminary List of Chemicals
Associated with Endocrine System Effects in Animals and Humans or In Vitro
(Illinois Environmental Protection Agency 1997). This is affirmed by several
other lists, according to the Pesticide Action Network (2000). In addition,
carbaryl is suspected of being a potential groundwater contaminant (Pesticide
Action Network 2000).

Carbaryl does not discriminate against organisms, and may kill many nontargeted species in areas where it is sprayed. These could include Newcomb's
littorine snail (Algamorda subrotundata), the previously mentioned Washington
State Candidate species and Federal Species of Concern (Washington Department
ofFish and Wildlife 2000a); the Pinto abalone (Haliotis kamtschatkana), also a
Washington State Candidate species; and the Dungeness crab, Cancer magister,
among other sensitive species.

As can be seen, the use of carbaryl against the green crab could pose
threats to human health and biodiversity. These issues should definitely be taken
into consideration when deciding whether or not to use carbaryl for the control of
Carcinus maenas.

Bounty programs
Bounty programs, both for green crabs and other species, have been used
with varying degrees of success in other regions of the country. They are not
52

currently used in Washington State for green crab control, with one exception.
Long-time oyster grower Lee Wiegardt runs his business, Jolly Roger OystersWiegardt Bros., Inc., at Willapa Bay. When green crabs were first discovered in
Washington, Mr. Wiegardt instituted a bounty system that paid $5.00 for each
green crab brought in. So few crabs were actually found that he eventually gave
up on the idea. In fact, only two were actually turned in-green crabs that had
been found one-half of a mile off shore in the oyster beds-and the "bounty
hunters" didn't even ask for their $5.00. Still, employees of Jolly Roger Oysters
are aware of the threat that the green crab imposes on the business, and Mr.
Wiegardt believes that some of the employees have taken a few green crabs home
and eaten them.

Bay scallops (Argopecten irradians) are, unfortunately, a favorite food of
green crabs, and some residents along the U.S. east coast have actually instituted
bounty programs on green crabs in order to try to decrease their scallop losses in
local salt ponds and bays (Fincham 1996; Walton 1997a). In the town of
Edgartown, on Martha's Vineyard, Massachusetts, bounty hunters are paid 40
cents a pound for green crabs. These usually end up on a compost pile
somewhere. One fisherman, Paul Bagnall, claims that the bounty program is
working, saying, "We have removed over 15,000 pounds of green crabs over the
last five months from this pond ... we have reaped the benefit of this by having a
scallop harvest up here this year. It isn't the best the pond has ever seen, but there
are certainly plenty of nice healthy scallops to be harvested" (Fincham 1996).

53

Edgartown destroyed about 22,000 pounds of green crabs trapped out of local salt
ponds in 1995 (Walton 1997a). William Walton, who has done a substantial
amount of research on green crabs in Martha's Vineyard, reports that the bounty
program has alternated with direct trapping by town managers, which is how most
towns approach the problem. In his own trapping surveys, he saw no obvious
drop in the catch per unit effort for such ponds using this combination of methods,
but adds that it wasn't possible to arrange a controlled test of the effect of
trapping. Also, the ponds likeliest to be trapped are the ones with the largest
green crab populations, so trapping ends up being correlated with "lots of green
crabs." He notes, however, that several fishermen have reported to him that they
have noticed drops in their green crab catches, enough so that it is not worthwhile
to continue to trap the crabs at the set bounty. In other words, if the bounty starts
to become effective, the fixed bounty drives the fishermen to stop trapping. His
conclusion? " ... bounty programs need to actively track the catch per unit effort
and increase the benefit as the pest becomes harder to catch" (Walton, personal
communication).

There has been some concern that bounty programs have the potential for
misuse. Perhaps there have already been instances where individuals have tried to
profit from such a program, since large amounts of money can sometimes be
made. For instance, a bounty program on the exotic pike minnow, found in the
Columbia and Snake Rivers and known to prey upon juvenile salmon, nets some
Washington fishermen up to about $40,000 a year (Rogers, personal
54

communication), although there has been no evidence of misuse in that particular
program. It is always possible that a green crab bounty program instituted at the
present time (when there are very few green crabs in Washington) has the
potential of motivating people to bring additional green crabs into Washington.
There is also a fear that if the green crab population explodes and a bounty
program is instituted afterwards, people may come to depend on the bounty
income and actually encourage breeding of green crabs on their private property,
or politically obstruct efforts to eliminate bounty programs if they are not working
well. Enforcement to ensure that bounty programs are not misused is timeconsuming and difficult at best. Yet evidence of misuse ofbounty programs
appears to be only anecdotal at the present. Two employees at the Nahcotta field
station ofthe Washington Department ofFish and Wildlife indicated that they
have not personally ever heard of a situation where a bounty program was
misused (Figlar-Barnes, personal communication; Randall, personal
communication).

Bounty programs appear to face some interesting limitations. If there are
too few organisms around, the program may fail simply due to "lack of interest,"
as was the case with Wiegardt's program. However, if a species such as the green
crab is very abundant, there is always the possibility that the government (or other
implementing entity) running the bounty program may have trouble keeping up
with the expense of paying bounty hunters. Still, bounty programs may be a
viable option in areas with significant numbers of green crabs, though more
55

research needs to be done on the topic. It has been noted that a bounty in
Washington at the present time might resolve the problem of aquaculture
employees merely smashing green crabs instead ofbringing them in to the
Department ofFish and Wildlife, and thus provide more data for the research that
WDFW is doing (Figlar-Bames, personal communication).

Fisheries
A related method for possible control of green crabs is the idea of
providing a subsidized fishery for them. Lafferty and Kuris (1996) suggest
utilizing subsidized fisheries in conjunction with biological control measures,
stating " ... after all, fisheries are a proven way to eradicate a species." They feel
that the green crab, being rather tasty (though too small for traditional commercial
seafood markets), might appeal to several ethnic groups, and they cite the example
of green crabs being split in two and added to miso soup in Japan (Lafferty and
Kuris 1996). Perhaps Lafferty and Kuris are on the right track, as green crabs
have not reached pest proportions in Japan. However, a fishery of this sort could
obviously only work if there were 1) very large numbers of green crabs and 2)
large numbers of people wishing to eat them, and is an idea probably best
reserved for areas like San Francisco, and not Washington, at the present time.

Green crabs in Maine recently made news due to a new study that will
look at selective harvest as a control strategy. The Beals Island Regional
Shellfish Hatchery is investigating the feasibility of harvesting green crabs for
56

specialty markets. It aims to find practical ways for fishermen to identify green
crabs, select ones in pre-molting condition, and then market them as a seafood
delicacy (Pacific Northwest Marine Invasive Species Team 2000).

In Europe, the green crab is fished commercially, and is used for both food

and bait. However, Cohen and Carlton (1995) state that the green crab's small
size (relative to other crabs) apparently precludes it from being part of the
commercial market in the United States, at least at the present time. Dumbauld
(personal communication) adds that selling green crabs as bait would send the
wrong message and be very dangerous, but if they were to be sold as bait in
Washington, one would have to make absolutely sure that they were dead.

Volunteer programs
Organizing volunteers and coordinating their efforts, if done properly, can
be a highly efficient way of making the best use oflimited resources. Fortunately,
the Washington Department ofFish and Wildlife has already been able to enlist
dozens of volunteers to assist the agency in its efforts to monitor and control the
European green crab. Many more are needed, both now and for future efforts.
Currently, about one-third of all green crabs in Willapa Bay and Grays Harbor
have been caught by volunteers. In the Puget Sound region, over 67% of the total
number of sites over the last three years have been monitored by volunteer groups
and individual volunteers (Sato, personal communication; Washington
Department ofFish and Wildlife 1999e; Washington Department ofFish and
57

Wildlife 200la). At times, volunteers have conducted up to 90% of the Puget
Sound monitoring effort (Rogers et al. 2000).

In the summer of 2000, a volunteer program was instituted at Willapa Bay,
with fairly good response. Volunteers were composed primarily of property
owners on the east side of Long Beach Peninsula (the west side ofWillapa Bay).
These volunteers monitored traps set out on their properties (typically crayfish
traps, in groups of three) and usually checked them daily for the presence of green
crabs, from May through September.

Andrea Randall, Washington Department ofFish and Wildlife, Nahcotta,
supervised the program, and plans to continue it in future summers. She reports
results on the volunteer program for the summer of 2000. After sending out
letters to all property owners in the area, Randall received 104 replies giving the
Fish and Wildlife Department permission to enter their land in order to set out
traps for green crabs. Nine persons wanted nothing to do with the situation.
Forty-two persons volunteered to trap. Twelve said they would trap, plus Fish
and Wildlife personnel could have access to their land. In the end, twenty-three
persons actually ended up going through WDFW's training program, and these
persons monitored traps on their properties throughout the summer.

For the summer of2001, 21 of these 23 persons indicated they would trap
agam. There was no response from the rest of the parties. Randall has high hopes
58

that the agency will be able to increase the number of volunteers at some point,
and feels that the response so far has been good (Randall, personal
communication).

As discussed in more depth in the "Early detection (monitoring)" section,
the Puget Sound region has had a substantial number of volunteers who have been
enlisted and trained by the Washington Department of Fish and Wildlife to set
crayfish traps and check them for green crabs. Adopt-a-Beach, whose volunteers
transferred over to the Puget Sound Restoration Fund when Adopt-a-Beach
became defunct, was the first volunteer organization to help in the coordination of
trapping efforts in the Puget Sound region. The Washington Department ofFish
and Wildlife now contracts with Puget Sound Restoration Fund on this effort,
paying $6,000 a season (March - September) to a part-time employee at the
Restoration Fund for coordinating the volunteers (Rogers, personal
communication). Other traps in the Sound region are checked by local tribes,
marine science centers, schools, shellfish growers, and concerned citizens-all of
them volunteers. The Washington Department ofFish and Wildlife in Brinnon
coordinates these activities.

Organizing volunteers effectively is always a very good option. In
Washington State, however, since the catch per unit effort has been declining
(Washington Department ofFish and Wildlife 1998-2000a; Washington
Department ofFish and Wildlife 1998-2000b; also see Figure 5), attempts to
59

organize volunteer efforts may become less fruitful if volunteers feel like they are
not making much of a difference. Whether the catch per unit effort is declining
because trapping efforts are working, or whether it is declining because
recruitment has not been significant, this issue needs to be analyzed.

Public education
In an excellent section of the Summary Report of the Green Crab 2000
Workshop held in Seattle, Sea Grant Oregon (2000) discusses needs and
opportunities for educating the public with respect to the European green crab.
Currently, west coast educational products on green crabs, either in the works or
already developed, include the following:
•
•
•
•
•
•
•
•
•

identification pamphlets
fact sheets
web sites
specimen display boards
training workshops
computer-based presentations
E-mail list servers
volunteer monitoring networks
videos

Suggestions concerning remaining needs included discussion of:
• producing a simple annual one-page update letter to shellfish growers,
who have been somewhat overdosed with green crab information and are
becoming disinterested since they have not yet been heavily affected by green
crabs. The thought was that this might keep the shellfish growers involved
without giving them an "overwhelming amount of education."
• educational materials for bait importers, bait shops, and anglers, since
green crabs are still imported via the bait market, particularly in California
(though this is now illegal in Washington).

60

• additional educational materials to reduce introductions via home
aquaria; the large pet store chain PetSmart has expressed interest in helping to
address this problem.
• involving mass media more, such as the newspapers.
• marketing educational products and workshops to non-profit
environmental organizations, which have commonly not gotten very involved in
aquatic nuisance species issues.

These are just some of the ideas and actions that have already been implemented
or proposed. Government entities in the state have been focusing on educational
efforts, as well.

The Washington State Aquatic Nuisance Species Committee (1998), in the
state's Aquatic Nuisance Species Management Plan, has recommended that Puget
Sound residents be educated about their role in preventing green crabs and other
exotic species from entering marine waters. This includes education on removing
organisms from boats and trailers before moving them from one marine area to
another (Washington Department ofFish and Wildlife 2001a).

In its most recent Sport Fishing Rules pamphlet, which gives seasons,
catch limits, and other information to anglers every year, the Washington
Department ofFish and Wildlife (2001-02) has a new advertisement: "Please
Don't Litter a Critter!!!" (see Figure 6). This informative little bulletin, which
features a picture of a European green crab, tells citizens what not to do when it
comes to furthering the spread of endangered species. Every notice such as this
61

Even careful citizens can accidentally
Introduce harmful plants and animals

Into our state waters.
So what's the problem?

Z e bra Mussel

Europe an

'
GreerfCrab

Outsldo of th lr native home some p lants and

animals can:
Cause billiOns or dollars worth of oc.onomlc CJamage
Cl'lpplo spon and oomme;-clal ~enes
Upset your re gio n·~ natural and ecological balance

Be a part of the solution!
•

Don'Crelease unwanted aquanum plants or
an mals lnco orur vaters
Don't launch your boat before removing all
hitchhok.mg plants und an1ma1s an d placing lhom
In the llash
Don't diSCard unwanted liYe bait or its packing
into the water
Don't release unwanted non-natwe hve seafood
or its paclung nto the wa ter
w e can all be part or the solu nand Pf6•ten t majar
environmental and eoonomic damage that can res.ult
from the presenoe of harm ful plants and animals.
For mare informabon v isit our aquatic nulsaooo
species wet site at http:IJ\ ,w w.wa.govl.vdfw (fi ~h and
S hellfi~ &elence) or oontad our coordinator at (360)

002·2724.

Protect Your Property and
Washin ton's Water Resources

Figure 6. Advertisement alerting public to the
problem of introducing non-native species
into state waters. (Source: Washington
Department of Fish and Wildlife 2001-2002)

62

one reaches one more person, and further spreads the word about non-native
species such as the green crab.

Finally, besides their usual monitoring efforts, the Washington
Department ofFish and Wildlife staff in Brinnon expend considerable time and
effort toward educating the public in and around Puget Sound. Interested
organizations and the general public are given presentations providing
background and identification information on the green crab, and most callers or
e-mailers with questions are sent a European green crab identification card
(Rogers et al. 2000). The Nahcotta branch ofWDFW at Willapa Bay also spends
time educating the public, schools, shellfish growers, and other interested parties
about green crabs, and what they can do about the problem.

As can be seen, much in the way of education is already being done.
Additional brainstorming on how best to educate both the general public and
specific sectors, and the carrying out of those ideas and plans, are essential if
Washington is to win the war against the green crab.

Biological control
Natural predators of the European green crab include fishes, gulls, and
other crabs; these predators keep the green crab in check in its native range. The
green crab is also vulnerable to certain parasites and egg predators. It is the latter
that offer the greatest hope of success in controlling non-native green crabs by
63

using biological control methods, according to Behrens Yamada (unpublished
manuscript). At the First International Workshop on the Demography, Impacts
and Management of Introduced Populations of the European crab, Carcinus
maenas, which was held in Tasmania in March of 1997, biological control was
one of two options suggested that were likely to be effective, out of the many
possibilities for green crab control {Thresher 1997). However, in many regions,
including the U.S. west coast, biological control using parasites and egg predators
is only in the preliminary stages of exploration. This section reviews current
biocontrol research and findings, with the hope of providing a convenient
summary and provoking thought about future options.

Hoeg, Glenner, and Werner (1997) have studied the parasitic isopod
Portunion moenadis for use as a biological control agent on the green crab. They
observed a 2% predation rate on green crabs in a study done on the west coast of
Sweden, where the green crab is native. Portunion maenadis essentially
feminizes and castrates the host crab (Behrens Yamada, unpublished manuscript);
the mode ofthis transformation is thought to be hormonal (Rasmussen 1973, as
cited by Behrens Yamada, unpublished manuscript). Too many details remain
unknown about Portunion maenadis at the present time to justify using it in any
field trials as a biological control agent (Hoeg, Glenner, and Werner 1997).

The parasitic barnacle, Sacculina carcini, is also known to infect green
crabs, robbing its host of nutrients, retarding molting, and castrating the crab,

64

regardless of sex. During a later state of infection, an external sac at the base of
the crab's abdomen is formed, to which the male Saccu/ina carcini larva attaches
itself (Behrens Yamada, unpublished manuscript). This sac contains the gonads
of the parasite, though it may resemble an egg mass, which causes both male and
female green crabs to exhibit brooding behavior such as cleaning, aerating and
protecting the sac. Larvae of the parasite may later be released (Crothers 1968, as
cited by Behrens Yamada, unpublished manuscript). The sac remains attached to
the crab for up to 6 months, after which the crab often dies (Rasmussen 1973, as
cited by Behrens Yamada, unpublished manuscript). Back in western Sweden,
Hoeg, Werner and Glenner (1997) discovered that one locality along the coast
showed 29.5% of green crabs infected with Sacculina carcini, and another locality
showed a 17.4% infection rate. They conclude that, if Sacculina carcini was
introduced in Australia, it would most likely infest green crab populations, but
add that further experimentation should be done first. Additionally, Minchin
(1997) investigated the influence ofthis parasite upon the green crab within its
home range. Though he found that green crabs were parasitized by Sacculina
carcini in all studies performed in Irish waters, Minchin feels that the potential
benefits of introducing this parasite to control invasive green crab populations are
small. Murphy and Goggin (2000) have done a recent study on the genetic
discrimination of sacculinid parasites and have noted the implications for control
of green crabs. Their data suggest that Saccu/ina carcini " .. .infests at least two
genera of crabs from a broad geographic distribution" and therefore may limit its
biological control prospects. In Australia, where Carcinus maenas is an invasive
65

species, Hoeg, Werner, and Glenner (1997) exposed green and other crabs to this
parasite in the laboratory. Carcinus maenas developed infections after exposure,
but fortunately, the native Paragrapsus gaimardii did not. However, it is not
known at this time whether Sacculina carcini could negatively affect Dungeness
and other native crabs on the U.S. west coast. In addition, although this parasite
heavily affects some green crab populations, others are left untouched (Behrens
Yamada, unpublished manuscript). Interestingly, Lafferty and Kuris (1996)
indicate that this parasite seems like the best candidate for biological control of
the green crab; they state it is highly host-specific and that present information
suggests it would be a safe control agent. But they do also stress the need for
carefully controlled experiments that could determine what effects, if any,
Sacculina carcini would have on native crab populations.

Two types of egg predators also offer hope in the area of biological
control. The first of these are the nicothoid copepods, small crustaceans that
complete their development as symbionts of crabs. Adult female nicothoid
copepods ( Choniosphaera cancrorum) resemble green crab eggs; they live in, and
move around freely within, the green crab's egg mass. Eventually they suck out
the contents of the crab eggs. The nicothoid copepods' egg packets also attach to
green crab eggs, and nicothoid larval stages live within the egg masses of the
green crab (Behrens Yamada, unpublished manuscript; Johnson 1957, as cited by
Behrens Yamada, unpublished manuscript).

66

The nemertean worms Carcinonemertes carcinophi/ia and C. epialti may
be useful in the control of green crab populations. These thin, elastic, nonsegmented worms (Behrens Yamada, unpublished manuscript) are also egg
predators. An attractive feature of Carcinonemertes epialti as a potential
biological control agent is that this particular species is already native to the U.S.
west coast. Torchin et al. (1996) have studied the infestation of green crabs by
Carcinonemertes epialti, and they report that it has already infected the green crab
population in Bodega Harbor, California. They feel that it could potentially
restrict the green crab's numbers. However, Lafferty and Kuris (1996) feel that it
is unlikely that this nemertean alone will affect green crab populations, since the
infestation rate is rather low. Other U.S. west coast crabs known to harbor
Carcinonemertes epialti include Hemigrapsus oregonensis (yellow shore crab, or
hairy Oregon shore crab), H nudus (purple shore crab) and Pugettia producta
(kelp crab) (Behrens Yamada, unpublished manuscript). The other nemertean
worm species, Carcinonemertes carcinophilia, has been found by MacGinitie and
MacGinitie (1968, as cited by Behrens Yamada, unpublished manuscript) to
parasitize the green crab in Europe. However, it had apparently not been found to
parasitize any green crab populations on the east coast ofNorth America at the
time of that report. Kuris (1997) has also studied nemertean egg predators and
made assessments of their use as potential biocontrol agents for the green crab.
He states that it seems " .. .likely that host specificity of C. carcinophilia is greater
than indicated by its current usage," but stresses that there are no direct studies of

67

its impact as an egg predator, and that additional research very much needs to be
done (Kuris 1997).

Additionally, Goggin (1997) looked at other parasites, excluding
Sacculina carcini, that could regulate populations of the green crab. After
studying various viruses, dinoflagellates, ciliates, and nemerteans, she came to the
conclusion that of those she studied, ciliates actually had the "best potential" for
biological control of green crabs. However, as seems to be the usual case with
potential biological control agents, she noted that extensive experimentation
would have to be performed, especially in order to discover whether native crab
populations could be threatened by the ciliates.

Behrens Yamada has also addressed the possibility of enhancing the
habitat for a native natural enemy-another approach to biological control:
On the West Coast ofNorth America it may be possible to
increase the abundance of native shore crabs in the high
intertidal zone of mudflats where green crab larvae settle out
from the plankton. This could be accomplished by adding
shelters such as rocks, stepping stones, plywood sheets and
oyster shells. Both shore crabs Hemigrapsus oregonensis and
H. nudus have been shown to colonize such newly created
shelters (Visser 1997, Ison 1998). Larger crabs typically
displace smaller crabs from shelters and often prey on them,
regardless of species ... Jensen et al. (2000) showed that the
shore crab H. oregonensis is a better competitor for shelter
than green crabs of similar size. It is thus conceivable that
adding shelter could give the native shore crabs a competitive
advantage over green crabs of smaller or equal size. Predation
of green crab recruits by the two Hemigrapsus species could
also occur. The outcome of such shelter addition on green crab

68

abundance would need to be investigated (Behrens Yamada,
unpublished manuscript).

Although it is clear that different forms of biological control may hold
promise for the suppression of green crabs, it is also apparent that much more
research is needed in this area. Since time is of the essence in many current
scenarios involving Carcinus maenas invasions, methods other than biological
control must be implemented while essential funding for further research on
biological control is pursued.

Genetic alteration
Little has been done in the way of research in this field, although there are
now a number of different molecular approaches for control and possible
eradication of pest species such as the green crab. These include
ploidy/chromosome manipulation, controlling the sex composition of populations
(via hormonal treatments and transgenic manipulation), immunocontraception,
and the introduction of inducible fatality genes via transgenic techniques (Grewe
1997). According to Grewe (1996, as cited by Grewe 1997), only the inducible
fatality gene "offers any real prospect of long-term control or even eradication" of
species like exotic carp, which Grewe has studied the most. He feels that these
concepts are "quite general and could be applied to other pest species," and states
reasons for considering the inducible fatality gene as being related to its long-term
application and its potential for 100% security (Grewe 1996, as cited by Grewe
69

1997; Grewe 1997). Thresher (1997) states that participants in the Australian
international workshop on green crabs of 1997 felt that approaches such as this
had considerable merit and were worth pursuing, although most noted they lacked
expertise in the area.

Can we predict future recruitment?
Green crabs were first observed in the State ofWashington in the summer
of 1998. It is currently believed that the mode of travel was "most likely a matter
of simple larval transport" (Dumbauld, personal communication). Ocean currents
flowing north from California, the original source of the west coast green crab
population, were thought to have been especially favorable for facilitating
transport of the crab larvae in the winter of 1997-98. Green crab ages were
remarkably similar when they turned up at sites in Oregon, Washington, and
British Columbia in 1998, indicating that they were probably all swept northward
in the same few-month period (Dumbauld, personal communication).

The 1998 larval recruitment was almost certainly related to the El Ni:fio
event of the winter of 1997-98, more specifically, the months between September
1997 and April1998. Although the El Nifio ocean conditions that year were
somewhat anomalous and extremely favorable for larval transport (Behrens
Yamada et al. 2000), range expansions of marine invertebrates and fish are
common observances during and after an El Nifio event (Schoener and Fluharty
1985, as cited by Behrens Yamada et al. 2000).

70

We can predict that a large-scale recruitment event like the one that
happened in 1998 will happen again. We can't always say exactly when, although
some scientists are now saying they have enough evidence to predict an El Nifio
in the coming winter of2001-2002 (Schmid 2001). Behrens Yamada et al. (2000)
forecast that the green crab will increase in abundance in both Oregon and
Washington, and that it will expand its range through dispersal of its larvae in this
manner.

A word on government incentives
When discussing the issue of how green crabs affect natural biodiversity
(see "Additional impacts upon biodiversity in Washington State" in this paper),
particularly with respect to "priority" species, it should be noted that the
Endangered Species Act does not require landowners to maintain or restore
habitats for listed species, let alone species of potential concern (Wilcove et al.
1998). (These species of potential concern include categories such as
Washington's State Candidate species-the Olympia oyster, Pinto abalone, and
Newcomb's littorine snail, among them.) Thus, for many private landowners,
including a company such as Weyerhaeuser that owns significant amounts of
property bordering Willapa Bay, there is no obligation to control for exotic
species such as the green crab. Nor is there much incentive, as the cost of
managing for invasive species can be considerable. At present, these costs are
usually not tax-deductible (Wilcove et al. 1998). Since the U.S. Fish and Wildlife
71

Service has less money to spend per species as the list of threatened animals and
plants steadily grows, it may become imperative to supplement the regulatory
controls of the ESA and other laws to provide incentives for landowners who
manage their property to benefit species in peril or species of potential concern
(Wilcove et al. 1996).

If no species of concern or potential concern exist on a property owner's
land, that does not diminish the threat of invasive species to the overall
environment or to commercial enterprises such as aquaculture. Perhaps
incentives, via tax breaks, could be offered to individuals or companies who work
with entities such as the Washington Department ofFish and Wildlife to manage
for invasive species along their shorelines. Implementation of such incentives
would be most easily accomplished by enacting legislation on a statewide level.
Since Washington State has no state income tax, perhaps such tax breaks could
come from the local property tax infrastructure.

72

CURRENT STATUS OF WASHINGTON STATE'S
GREEN CRAB POPULATION AND RESPONSE

Population status
Figure 4 (found on page 46) shows the locations where the Washington

Department ofFish and Wildlife has placed green crab traps in Willapa Bay and
Grays Harbor. The figure shows sites where green crabs have, or have not, been
captured to date. In Willapa Bay, 50 ofthe 73 survey sites have resulted in green
crab captures; in Grays Harbor, exactly half(27) of the survey sites have netted
one or more green crabs.

The majority ofWDFW's coastal trap checking is done from April
through September. Monthly monitoring is done at three locations in Willapa
Bay and two locations in Grays Harbor. In August and September, large baywide
surveys are conducted at over 20 sites in the bays. Similar surveys continue to be
performed during other months of the year. Most traps are "rotated" into different
sites in order to provide a more comprehensive picture of green crab distribution,
although some remain in the same spots as controls. Thus, sites (exclusive of
monthly sites) end up being checked an average of3-5 times during the summer
months. Volunteer property-owners and others are encouraged to check their
traps as often as possible and strive for once every 24 hours (Dumbauld, personal
communication; Rogers et al. 2000).

73

The large majority of green crabs captured in Willapa Bay and Grays
Harbor have been found in the intertidal areas from April to October each year.
Most of these, by far, have been in the low saltmarsh and either in Spartina
habitat (the introduced cordgrass) or in Triglochin (native arrowgrass) and Scirpus
(American threesquare) territory (Rogers et al. 2000). At the present time, green
crabs tend to be found more in higher salinity areas near the mouth of Willapa
Bay, such as the eastern side of Long Beach peninsula (which is the west side of
the Bay), or in the more northern half of the bay. This is probably not due to
salinity factors, but to the fact that these locations are near the mouth of the
estuary (Dumbauld, personal communication; also see Figure 4).

In the winter (late October to March), green crabs can no longer be found
in the intertidal areas of Washington bays, but have moved into deeper subtidal
waters. The reason for this seasonal movement is not entirely clear, but it may
have to do with retreat by the crabs to areas of higher temperature and salinity
(Rogers et al. 2000). Any crabs captured in these winter months are usually found
in shell bags or via dredging activities by oyster growers, although the majority of
green crabs that growers turn in are found in the spring in oyster seed bags
(Dumbauld, personal communication; Rogers et al. 2000).

The Washington Department ofFish and Wildlife's field station in
Nahcotta keeps detailed records of their trap-hours, and the number of green crabs
captured in these traps. Their catch per unit effort has fallen substantially from
74

1998 to the year 2000, which is good news (see Figure 5 on page 47; note 2001
CPUE figures are not yet available). In 1998, WDFW's CPUE was 0.015 crabs
per trap-hour in Willapa Bay (197 crabs divided by 13,374 hours); in 1999, CPUE
in Willapa Bay was 0.003 (264 crabs divided by 93,327 hours), and in 2000,
CPUE was 0.002 (101 crabs divided by 63,288 hours). For Grays Harbor, CPUE
has been approximately even at 0.001 crabs per trap-hour for the years 1999 (29
crabs divided by 24,648 hours) and 2000 (21 crabs divided by 15,240 hours).
Trap-hour data for 1998 are not available for Grays Harbor (Washington
Department ofFish and Wildlife 1998-2000a; Washington Department ofFish
and Wildlife 1998-2000b).

Table 2 breaks down the numbers and sexes (including ovigerous
females) of green crabs found in both Willapa Bay and Grays Harbor from the
years 1998 through 2000. These numbers represent all green crabs caught in the
bays, not only by WDFW, but also by local oyster growers, landowners, students,
and the Shoalwater tribe. Table 2 also notes the size range of the crabs during
those years. As one can see by the table, there has not been as much of a decrease
in crabs caught in Grays Harbor (39% from the peak year 1999 to the year 2000)
as there has been in Willapa Bay (a 58% decrease from the peak year 1999 to the
year 2000) (Washington Department ofFish and Wildlife 1998-2000a;
Washington Department ofFish and Wildlife 1998-2000b). This difference
between the two locations may be a reflection of trapping efforts paying off more
in Willapa Bay, where the Department ofFish and Wildlife is able to expend
75

Grays Harbor

Willapa Bay

-..l

Females

Unsexed

203

100

1

1999

239

103
3 w/eggs

5

2000

104

41
2 w/eggs

0

All years

546

244

6

Year

Males

1998

0\

%

decline
from
1999-2000

Size
Range
(mm)

Total

Males

Females

Unsexed

25.766.0

304

21

8

1

30.376.8

347

108

15
2 w/eggs

1

19.3 90.0

145

63

13
1 w/eggs

0

796

192

36

2

58% decline
from
1999- 2000

Size
Range
(mm)
25.358.3

27.778.0

32.782.1

Total

30

124

76

230

39% decline
from
1999-2000

Table 2. Numbers and genders of green crabs caught in Willapa Bay and Grays Harbor, Washington, from 1998 to 2000.
(Source of data: Washington Department of Fish and Wildlife 1998-2000a; Washington Department of Fish and Wildlife 1998-2000b)

more of its time and energy. lfthat is true, it would also follow that green crab
populations are not going down "naturally" simply due to a lack of recruitment.

In fact, (see Figure 7 and Figure 8), data indicate that small crabs of a
new year class have appeared in both 2000 and 2001 (the figures exhibit data from
the years 1998-2000). This indicates that either further recruitment has occurred
in both bays, or that crabs in both bays are reproducing. Analyzing the 2001
trapping effort results will be important in learning whether a self-sustaining
population has been established in Willapa Bay and Grays Harbor (Washington
Department ofFish and Wildlife 2001a). As of June 2001, the same numbers of
crabs have been found so far this year (2001) as in the year 2000 (Figlar-Barnes,
personal communication) instead of going down, as they have in previous years.

So, the good news: trapping is working. The "bad" news? The
Washington Department ofFish and Wildlife probably won't know until later in
the year (2001) how well that trapping has worked, and whether it will have been
enough to keep self-sustaining green crab populations from becoming established.

77

100.
88.

-ee
-....
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00

77.u~

I

66.7

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~-~~-9n:

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1998

1999

2000

Figure 7. Sizes of green crabs found in Willapa Bay, Washington, for years 1998-2000. Each small
circle represents one crab.
(Original chart: Figlar-Barnes and Randall2001)

100.088.9=
00 0

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11.10 .0+---__l--,-__l_ _--L..---,---L----...__.-...___ _--,
1998

1999

2000

Figure 8. Sizes of green crabs found in Grays Harbor, Washington, for years 1998-2000. Each small
(Original chart: Figlar-Barnes and Randall 2001)
circle represents one crab.

Funding for green crab programs
In 1998, the year the European green crab was discovered in Washington's

waters, Governor Gary Locke provided $110,000 in emergency funds for the
fiscal year 1999 (which ended in June of 1999). Employees at the Washington
Department ofFish and Wildlife began searching for crabs and collecting them
even before the emergency funds were provided (Dumbauld, personal
communication). These emergency funds were then used to immediately begin
large-scale monitoring and control efforts in both the Puget Sound region and on
Washington's coast. Fortunately, the effort did not stop there. Funding for green
crab control was continued in the 1999-2001 biennium (which ran from July 1999
through June of2001). The state allocated $464,000 and 3.5 FTEs (full-time
employees) for the biennium; $40,000 of this amount was for one-time start-up
costs (Olsen, personal communication; Washington Department ofFish and
Wildlife 1999b). I should note that many staff and legislators worked hard to see
this funding implemented, but State Senator Ken Jacobsen has perhaps been this
effort's greatest champion. It is due to the far-sightedness of Jacobsen and others
that Washington State's green crab control and monitoring programs exist today.

Because of the current (2001) budget deficits in Washington State,
Governor Gary Locke imposed a mandate at the beginning of the year 2001 that
all agencies, across the board, cut their budgets. There were worries in early 2001
that funding for the green crab program would be reduced or eliminated. After
all, the present allocation is a fairly large sum of money and, in addition, there
80

l
may be the perception that green crabs are not of immediate concern; they have
done no damage that the government or the public can discern at the present time.

The over $400,000 that has been allocated to Washington State's green
crab programs comes from the state's general fund (state appropriation), with the
Washington Department ofFish and Wildlife as the implementing entity. For
now, the general fund continues to supply this appropriation. Approximately half
of the amount is used for the Puget Sound region, and the other half for Willapa
Bay and Grays Harbor (Smith, personal communication). Funding for the green
crab program is provisional, and is directed specifically at green crabs (Rogers,
personal communication). The state general fund is, by far, the major source of
the green crab program's funding. The Washington Department of Wildlife does
receive small amounts of funding from other sources, generally not more than a
few thousand dollars annually, specifically for green crab monitoring and control.
For instance, the National Invasive Species Act (NISA), through the
implementing entity of the U.S. Fish and Wildlife Service, provides the Aquatic
Nuisance Species Division of WDFW with some funding, but only an estimated
$3,000 annually goes toward the green crab programs (Smith, personal
communication).

Fortunately for the green crab programs, it appears that the 2001-2003
biennium will see the state's general funding stay in place, minus the original
$40,000 one-time start-up costs (Olsen, personal communication). This means
81

that the state will be providing a total of$424,000 for the upcoming two-year
period.

82

CONCLUSIONS: LESSONS FROM
WASHINGTON STATE'S EXPERIENCE

Upon their discovery that nearly half of imperiled species in the United
States are threatened by alien species, and recognizing that numbers of alien
species are steadily growing, Wilcove et al. (1998) have made the statement that
" ... this particular threat may be far more serious than many people have heretofore
believed." Any lack of continued attention to this threat in Washington may
determine whether the European green crab does indeed thoroughly invade our
ecosystems. I believe that if we do not continue to address the problem, it will.
.j

Given the circumstances, especially budget constraints, the State of
Washington has responded admirably to the threat of a green crab invasion. Time
will tell how well these efforts have paid off, but it appears at the present that the
state has made good decisions and choices in its handling of the situation. Up to
this point in time, the Washington green crab plan can be seen as a good model
for other states to follow when dealing with threats of marine invasions and/or
invasions in early stages.

The state has also made efficient use of resources by combining efforts
addressing more than one invasive species. This ultimately has resulted in the
passage of legislation that not only deals with green crabs, but also with other
invasive species such as the Zebra mussel (for examples of this legislation, see the

83

"Prevention measures" section earlier in this paper). In fact, the state combined
efforts to focus on Zebra mussels and green crabs by forming the Zebra Mussel
and European Green Crab Task Force, which first met on September 17, 1998,
and which approved a final report and recommendations on November 20, 1998.
This task force consisted of 86 members and was organized into two committees
(the Zebra Mussel Committee and the Green Crab Committee) and four subcommittees. The two committees provided education resources and assisted each
sub-committee in developing recommendations and a final report. The four subcommittees were established to address each major pathway of potential
introduction of invasive species-aquatic plant and animal suppliers, ballast
water, aquaculture and live seafood industry, and recreational boating.
Recommendations were developed for each of these areas, and subsequent
legislation showed that the Task Force's efforts had been taken seriously. The
Task Force also ended up recommending as high priority (among other things)
that green crab monitoring and control programs be continued and expanded, and
estimated a biennium funding level of $464,788, which the state granted during
the following legislative session (Washington Department ofFish and Wildlife
1999c).

Even before the arrival of the green crab in Washington, government and
private entities were working on developing the Aquatic Nuisance Species
Management Plan, a comprehensive management strategy to address important
aquatic nuisance species issues (Washington Department ofFish and Wildlife
84

significantly correlated with increasing abundances of green crabs in Bodega Bay,
California (Grosholz 1997). The Washington Department ofFish and Wildlife
(2001a) states that nearly three dozen mussels under 45 mm in length may be
eaten daily by one green crab, and Wilhelm (2000) reports that a green crab can
eat more than 40 young shellfish per day. Regarding the Dungeness crab fishery,
the McDonald et al. (2001) laboratory trials showed green crabs consistently outcompeting equally-sized Dungeness crabs for food and shelter sources; Cohen et
al. (1995) and Grosholz and Ruiz (1995) report that the Dungeness crab can be
consumed by green crabs at up to the green crab's own size. Given all these
figures, it is very much within the scope of reason that a large-scale green crab
invasion could affect 20% of existing fisheries and shellfish industries within the
State of Washington. This, therefore, amounts to annual state losses of
approximately $24 million (the estimate of dollars lost does not, of course,
include the hard-to-define costs ofloss ofbiodiversity and damage to noncommercial species).

Given the scarcity of monetary resources available in Washington State,
are we relegating an appropriate amount of money toward green crab detection
and control? I certainly believe so-$424,000 seems well spent when examining
a potential scenario of $24 million in annual loss to state industry. Are we
utilizing the best current detection methods in the Puget Sound region and the best
current control methods in the Willapa Bay and Grays Harbor areas? I feel that
we are. But I also believe that these need to be expanded.

86

1

l
RECOMMENDATIONS

More funds need to be allocated overall to the green crab program in
Washington State. The Washington Department ofFish and Wildlife has done,
and is doing, a fantastic job of green crab monitoring and control statewide with a
current budget of not much more than $424,000. In order to ensure that the
groundwork they have laid and the research they have done does not go to waste,
these efforts need to be expanded, as noted in the following paragraphs. Table 3
summarizes these recommendations for green crab control and monitoring efforts
in the future.

Specifically, additional funding should be used toward increasing the
number of monitoring sites in the Puget Sound region, to include new sites
monitored by WDFW, and-especially-additional sites to be checked by
volunteers. Organizing volunteers and coordinating their efforts is one of the very
best ways to make the best use of limited resources. It seems wasteful not to
allocate additional funds for the purposes of coordinating volunteer efforts.
Recall that the Puget Sound WDFW contracted last season (March - September
2000) with the Puget Sound Restoration Fund to hire a part-time coordinator
responsible for organizing and monitoring volunteers. Last year (2000), this
resulted in 37 additional monitoring locations being checked around the regionroughly one-fifth of all locations in the Puget Sound area-all for the relatively
small price of$6,000! Adding $12,000-$18,000 to the Puget Sound region's
87

biennial budget in order to pay 2 to 3 more non-profit organization coordinators to
monitor networks of volunteers could result in an additional 70 to 105 traps being
monitored. This increase in the number of monitoring sites is essential in order to
ensure that any green crabs are detected as early as possible. It is fortunate that
the Washington Department ofFish and Wildlife has already been able to enlist
dozens of volunteers to assist with efforts to both monitor and control the
European green crab. Many more are needed in the future-but with wellorganized volunteer programs, Washington State will get more than it pays for.

Having trouble coming up with volunteers or volunteer organizations?
Why not expand the list of groups under consideration? For instance, there are
several hunting and fishing organizations and clubs that may be amenable to
volunteering to check traps. Such groups are usually quite conservation-minded,
and also may perceive that they will reap the benefits of heading off a green crab
invasion--especially avid clammers, crabbers, and the like.

It is extremely important that more attention be given to Grays Harbor,

where WDFW does not currently have the time or the funds to set up and
coordinate an extensive trapping network. Trapping efforts, it appears, do work
(see the "Population status" section) and so, obviously, we should be doing more
trapping. At least one additional full-time position is warranted in order to
adequately cover program needs in Grays Harbor. Grays Harbor has as much
potential for a green crab explosion as Willapa Bay, but limited resources and
88

time have resulted in WDFW focusing far more oftheir efforts on Willapa Bay,
where their field station is located.

And what about the possibility of another large recruitment event? It
almost certainly will happen. Additionally, the population explosion and range
expansion ofthe green crab on the U.S. east coast has been correlated with a rise
in ocean temperatures around the turn ofthe twentieth century (Rogers 2001a). If
this same trend holds true on the U.S. west coast, the green crab problem can only
be exacerbated by predicted climate changes. State governments are not normally
in the habit of preparing for disasters that are not somewhat imminent (and with
limited budgets, who can blame them?). But the state needs to be mindful that it
'

'I'

may suddenly need to come up with additional funding in the event of another
recruitment incident, and a certain level of preparedness is warranted. This may
include strategies such as devising a good emergency response plan ahead of time
or being ready to quickly install additional personnel in sites such as Grays
Harbor. Of course, one of the best ways to be prepared is to have the "prerecruitment event" situation firmly under control. This is why it is imperative that
we step up Puget Sound monitoring efforts and Grays Harbor trapping practices as
soon as possible.

And where do these additional funds come from? Although I would make
the argument that one more full-time employee in Grays Harbor, and 2 or 3 more
allocations of $6,000 (to be used for contracting with volunteer organizations to
89

coordinate trap checking), does not equal a large sum of money, it does need to
come from somewhere. If the state cannot provide this additional insurance
money on its own, perhaps a tax could be placed upon the persons who reap the
benefits ofbeautiful shorelines and trouble-free waters. Adding a small tax to,
say, a State of Washington Recreational License could bring in additional
revenue. A growing number of people seem to be aware ofthe potential problems
associated with exotic invasions; they might be quite amenable to a "nuisance
species prevention tax." Hunters and fishermen in particular, as I have already
mentioned, are often quite conservation-minded, and may be willing to bear this
small added expense.

Public education can be inexpensive, and sometimes it can be free.
Enlisting the media's help in drawing attention to the green crab problem may be
one way of educating the public, not only on identification of green crabs, but on
the dangers of toting them around. Increased attention should also be given to
addressing education in specific sectors of the public. Ideas such as the ones
found in the "Public education" section in this paper are invaluable, and more
workshops addressing these outreach and education issues may generate even
more ideas and spur further action.

What is the scientist's role in addressing these issues? A good start would
be to tum more attention to biological control research. As Lafferty and Kuris
( 1996) state, "The absence of studies on the control of introduced marine and
90

estuarine pests approaches fatalism." They feel it is odd that there has been so
little response to exotic invasions by researchers and management agencies, given
that biological control has such a long track record of remarkable successes in
agriculture, and since the field has been so well established and analyzed.

Last, scientific research and facts relating to the impact of green crabs on
non-commercial, and sometimes threatened, species now also need to be added to
the arguments for controlling Carcinus maenas and other invasive species. We
cannot afford to overlook these important issues ofbiodiversity, and their added
weight may help tip the scales toward retention of, and increases in, crucial
funding for control of exotic species.

The real question is not whether we should address a green crab invasion,
but how, and how fast. One option not mentioned in the control section of this
paper is the option of doing nothing at all. There is a train of thought that believes
that humans should succumb to the inevitability of exotic species invasions, and
sit back and watch our existing "natural" environments morph into different ones.
Not only are out-of-control exotic invasions not inevitable, I believe that most
persons-from shellfish growers, to ecologists, to concerned citizens--do not
wish to see "different" environments that have been altered by invasive species.
We like what we have! And if this is so, our elected officials and policy makers
must listen. If they do not, it is inevitable that Carcinus maenas will infest the
waters of Washington State, and it will only be a matter of when. Our current

91

green crab prevention, detection, and control programs are comparable to a
homeowner who pays annually for flood insurance when living in a flood plain.
The homeowner knows that the floods will come. The homeowner also knows
that the floods may not come in his or her lifetime, but nonetheless does not risk
suffering the loss. Washington State's scenario is nearly the same, with one
exception: green crabs are only around the bend of the next river. Economic and
environmental disaster flow in their wake, and we owe it to ourselves to pay the
insurance premiums before we no longer have a choice in the matter-and in
doing so, we may very well provide our neighbors with a good example, too.

92

1) Increase number ofmonitoring sites in the Puget Sound region-specifically,
increase sites that can be monitored by volunteers by 70-105 sites
2) Achieve goal1) by adding $12,000-$18,000 to Puget Sound region biennial
budget in order to pay 2 to 3 more non-profit organization coordinators (at $6,000
apiece) to monitor networks of volunteers
3) Increase efforts made to enlist and coordinate volunteers utilizing expanded list
of volunteer and not-for-profit organizations, such as hunting and fishing groups
4) Increase staff in Grays Harbor by at least one full-time position in order to
expand and concentrate on additional trapping and monitoring sites
5) Prepare emergency response plan in event of sudden influx of green crabs; this is
of particular importance if another El Nifio is predicted
6) Explore the possibility of a "Nuisance Species Prevention Tax," to come from
sources such as State of Washington Recreational Licenses, as a source for
additional funding for green crab programs
7) Investigate cost-effective ways to increase public education, which may include
enlisting the help of media sources
8) Fund at least one position for long-term study investigating past, present and
possibly future methods ofbiological control
9) Scientists should continue to research existing impacts of green crabs on
aquaculture and fisheries, particularly in field experiments (primarily in places such
as California, where green crabs are already abundant and can be studied readily)
10) Take into consideration potential impacts of green crabs on non-commercial
species of concern, such as threatened/sensitive species listed in Table 1

Table 3. Recommendations for future green crab control and monitoring efforts in
Washington State.

93

BIBLIOGRAPHY

Aasen, S. (1997). Willapa Bay's Oyster Industry: Control ofSpartina and
Burrowing Shrimp. MES Thesis, The Evergreen State College, Olympia, WA.
Behrens Yamada, S., C. Hunt, and N. Richmond (2000). The arrival ofthe
European green crab, Carcinus maenas, in Oregon estuaries. Proceedings of the
First National Conference on Marine Bioinvasions: January 24-27, 1999. J.
Peterson, ed. Massachusetts Institute of Technology Sea Grant Program,
Cambridge (MA).
Behrens Yamada, S. (unpublished manuscript). A Global Invader: The European
Green Crab. Oregon and Washington Sea Grant, in press.
Biocontrol News and Information (1999). Aliens make waves. Biocontrol News
and Information web page, Vol. 20, No. 1. <http://pest.cabweb.org/Journals/
BNI!Bni20-1/gennews.htm>
British Columbia Shellfish Growers Association (2001). Industry overview. Last
updated March 30, 2001. Duncan, B.C. <http://www.island.net/~bcsga/
overview.htm>
Campbell, S., and K. Riener (1992). Burrowing Shrimp Control in Willapa Bay:
Research Needs and Alternatives to Chemical Control. MES Thesis, The
Evergreen State College, Olympia, WA.
Carlton, J. T., and A. N. Cohen (1995). Episodic global dispersal in shallow
water marine organisms: the case history of the European green crab Carcinus
maenas. Submitted to Journal ofBiogeography.
Ching, H. L. (1989). Profilicollis botulus (Van Cleave, 1916) from diving ducks
and shore crabs ofBritish Columbia. Journal ofParasitology 75:33-37.
Cohen, A. N., and J. T. Carlton (1995). Nonindigenous Aquatic Species in a
United States Estuary: A Case Study of the Biological Invasions of the San
Francisco Bay and Delta. Washington, D.C.: US Fish and Wildlife Service,
December, 1995.
Cohen, A. N., J. T. Carlton, and M. Fountain (1995). Introduction, dispersal and
potential impacts of the green crab Carcinus maenas in San Francisco Bay,
California. Marine Biology 122:225-237.

94

Crothers, J. H. (1968). The biology ofthe shore crab Carcinus maenas (L). 2.
The life ofthe adult crab. Field Studies 2:597-614.
Dickey, P., Washington Toxics Coalition, Seattle, WA. Personal communication,
May, 2001.
Dumbauld, B., Washington Department ofFish and Wildlife. Personal
communication, January, May, 2001.
Environmental Inquiry (2001) web page. "Invasive species." Cornell University
and Penn State University. <http://ei.cornell.edu/ecology/invspec/>
Figlar-Barnes, R., Washington Department ofFish and Wildlife. Personal
communication, May, 2001.
Figlar-Bames, R., and A. Randall (2001). Coastal green crab project-update
report. Washington Department ofFish and Wildlife, March, 2001.
Fincham, M. (1996). An endless invasion? Green crabs, New England intruders,
move west. Maryland Marine Notes March-April1996, 14(2). <http://www.
mdsg.umd.edu/MarineNotes/Mar-Apr96/>
Goggin, L. (1997). Parasites (excluding Sacculina) which could regulate
populations of the European green crab Carcinus maenas. Proceedings of the
first international workshop on the demography, impacts and management of
introduced populations of the European crab, Carcinus maenas: 20-21 March
1997. Centre for Research on Introduced Marine Pests, Hobart, Tasmania,
Australia. Technical Report 11.
Grewe, P. (1996). Review and evaluation ofthe potential of molecular
approaches for the environmentally benign management of the common carp
(Cyprinus carpio) in Australian waters. Technical Report Number 10, Centre for
Research on Introduced Marine Pests. CSIRO Division of Fisheries. October,
1996.
Grewe, P. (1997). Molecular approaches for the environmentally benign
management of pest species. Proceedings of the first international workshop on
the demography, impacts and management of introduced populations of the
European crab, Carcinus maenas: 20-21 March 1997. Centre for Research on
Introduced Marine Pests, Hobart, Tasmania, Australia. Technical Report 11.
Grosholz, E. D., and G. M. Ruiz (1995). Spread and potential impact of the
recently introduced European green crab, Carcinus maenas, in central California.
Marine Biology 122:239-247.
95

---,
l
l•
'

Grosholz, E. D. (1997). The impact ofthe introduced European green crab on
benthic invertebrates in Bodega Harbor, CA. Proceedings of the first
international workshop on the demography, impacts and management of
introduced populations of the European crab, Carcinus maenas: 20-21 March
1997. Centre for Research on Introduced Marine Pests, Hobart, Tasmania,
Australia. Technical Report 11.
Grosholz, E. D., and P. Olin (2000). Reducing losses of Manila clams to the
European green crab. California Sea Grant/University of California Cooperative
Extension leaflet.
Hoeg, J., H. Glenner, and M. Werner (1997). The epicaridean parasite Portunion
moenadis as a biological control agent on Carcinus maenas. Proceedings of the
first international workshop on the demography, impacts and management of
introduced populations of the European crab, Carcinus maenas: 20-21 March
1997. Centre for Research on Introduced Marine Pests, Hobart, Tasmania,
Australia. Technical Report 11.
Hoeg, J., M. Werner, and H. Glenner (1997). The parasitic castrator Saccu/ina
carcini as a possible biological control agent of Carcinus maenas: background
and results of preliminary work. Proceedings of the first international workshop
on the demography, impacts and management of introduced populations of the
European crab, Carcinus maenas: 20-21 March 1997. Centre for Research on
Introduced Marine Pests, Hobart, Tasmania, Australia. Technical Report 11.
Hunt, C. (2000). Potential limitations of the European green crab, Carcinus
maenas, in habitat suitable for the native red rock crab, Cancer productus.
Abstract from 2000 annual meeting, National Shellfisheries Association, Seattle,
WA, held March 19-23,2000.
Hunt, C., and S. B. Yamada (2001). Predation by the red rock crab, Cancer
productus on the European green crab, Carcinus maenas. Proceedings of the
Second International Conference on Marine Bioinvasions: April9-11, 2001.
Massachusetts Institute of Technology Sea Grant Program, Cambridge (MA),
p. 75.
Illinois Environmental Protection Agency (1997). Illinois EPA Endocrine
Disruptors Strategy. Table obtained from an EPA Internet web page (last revision
February 22, 2001) on June 6, 2001 at the following address: <http://www.epa.
gov/ord/spc/endoqs.htm>
Information Ventures, Inc. (1995). Carbaryl, pesticide fact sheet. Prepared for
the U.S. Department of Agriculture, Forest Service. <http://www.infoventures.
com/e-hlth/pesticide/carbaryl.html>

96

Ison, T. (1998). Using artificial cover as a sampling method of shore crab density.
<http://ucs.orst.edu/~yamadas/crab/ch6.htm>
Jacobsen, K., Washington State Senator. Personal communication, April, 2001.
Jensen, G. C., P. S. McDonald, and D. A. Armstrong (2000). East meets west:
competitive interactions between green crab, Carcinus maenas and Hemigrapsus
spp. Submitted. Abstract in Journal ofShellfish Research 19(1 ):632.
Johnson, M. W. (1957). The copepod Choniophaera cancrorum parasitizing a
new host, the green crab Carcinus maenas. Journal of Parasitology 43:470-473.
Kaiser, M. J., R.N. Hughes, and D. G. Reid (1990). Chelal morphometry, preysize selection and aggressive competition in green and red phase of Carcinus
maenas. Journal ofExperimental Marine Biology and Ecology 140: 121-134.
Kuris, A. (1997). Nemertean egg predators as potential biocontrol agents for
Carcinus maenas. Proceedings of the first international workshop on the
demography, impacts and management of introduced populations of the European
crab, Carcinus maenas: 20-21 March 1997. Centre for Research on Introduced
Marine Pests, Hobart, Tasmania, Australia. Technical Report 11.
Lafferty, K. D., and A.M. Kuris (1996). Biological control of marine pests.
Ecology 77(7): 1989-2000.
LeRoux, P. J., G. M. Branch, and M.A. P. Joska (1990). On the distribution, diet
and possible impact of the invasive European shore crab Carcinus maenas (L.)
along the South African coast. South African Journal ofMarine Science 9:85-92.
Liat, L. B., and A. W. Pike (1980). The incidence and distribution of Profi/icol/is
botulus (Acanthocephala), in the eider duck, Somateria mol/issima, and in its
intermediate host the shore crab, Carcinus maenas, in north east Scotland.
Journal ofZoology (London) 190:39-51.
MacGinitie, G. E., and N. MacGinitie (1968). Natural History ofMarine
Animals, second edition, McGraw-Hill Book Company: New York, NY.
McDonald, P. S., G. C. Jensen, and D. A. Armstrong (2001). The competitive
and predatory impacts of the nonindigenous crab Carcinus maenas (L) on early
benthic phase Dungeness crab Cancer magister Dana. Journal ofExperimental
Marine Biology and Ecology 258(1 ):39-54.
McKnight, A., L. M. Mathews, R. Avery, and K. T. Lee (2000). Distribution is
correlated with color phase in green crabs, Carcinus maenas (Linnaeus, 1758) in
southern New England. Crustaceana 73(6):763-768.
97

Meister, R. (ed.) (2000). Farm Chemicals Handbook 2000 (Vol. 86).
Willoughby, OH: Meister Publishing Company.
Milne, D., The Evergreen State College, MES Program. Personal
communication, April, 2001.
Minchin, D. (1997). The influence ofthe parasitic cirripede Saccu/ina carcini on
its brachyuran host Carcinus maenas within its home range. Proceedings of the
first international workshop on the demography, impacts and management of
introduced populations of the European crab, Carcinus maenas: 20-21 March
1997. Centre for Research on Introduced Marine Pests, Hobart, Tasmania,
Australia. Technical Report 11.
Murphy, N. E., and C. L. Goggin (2000). Genetic discrimination of sacculinid
parasites (Cirripedia, Rhizocephala): implication for control of introduced green
crabs (Carcinus maenas). Journal ofCrustacean Biology 20(1):153-157.
Olsen, J., Fiscal Analyst, Appropriations Committee, Washington State Office of
Program Research. Personal communication, May, 2001.
Pacific Biodiversity Institute. Endangered species information network for the
Pacific Northwest. Retrieved May 10,2001 from <http://www.pacificbio.org/
ESIN/ESIN.html>
Pacific Northwest Marine Invasive Species Team (PNW MIST) (2000). Aquatic
non-native species update, November, 2000. <http://seagrant.orst.edu/mist/
ans112000.html>
People for Puget Sound (1996). Shellfish and the Sound economy. The
Partnership for a Sound Economy web page. <http://www.pugetsound.org/
economy/shellfish.html>
Pesticide Action Network (2000). PAN Pesticide Database: information about
carbaryl. <http://data.pesticideinfo.org/4Daction!GetChemRecord!PC3281>
Pimentel, D. (1999). America's alien invasion. American Association for the
Advancement of Science conference, Anaheim, CA, January 25, 1999. <http://
news. bbc.co. uklhi/englishlsci/tech/specials/anaheim_99/newsid_ 262000/262899.
stm>
Pimentel, D., L. Lach, R. Zuniga, and D. Morrison (2000). Environmental and
economic costs associated with non-indigenous species in the United States.
Bioscience 5(1 ).
98

l

Proctor, C., and R. Thresher (1997). The invasive history, distribution and
abundance of C. maenas in Australia. Proceedings of the first international
workshop on the demography, impacts and management of introduced
populations of the European crab, Carcinus maenas: 20-21 March 1997. Centre
for Research on Introduced Marine Pests, Hobart, Tasmania, Australia. Technical
Report 11.
P1;1get Sound Water Quality Action Team (2000). Puget Sound online: Puget
Sound's health 2000. Last updated May 22, 2001. <http://www.wa.gov/
puget_soundlindex.htm>
Randall, A., Washington Department ofFish and Wildlife. Personal
communication, May, 2001.
Rasmussen, E. (1973). Systematics and ecology of the Isefjord marine fauna
(Denmark) with a survey of the eelgrass (Zostera) vegetation and its communities.
Ophelia 11:1-507.
Rayski, C., and E. A. Garden (1961 ). Life-cycle of an acanthocephalan parasite of
the eider duck. Nature (London) 192:185-186.
Richter, B. D., D.P. Bran, M.A. Mendelson, and I. L. Master (1997). Threats to
imperiled freshwater fauna. Conservation Biology 11:1081-1093.
Rogers, R., R. Figlar-Bames, and B. Dumbauld (2000). Monitoring and Control
of the European Green Crab (Carcinus maenas) in Washington State: A Report to
the Legislature. Washington Department ofFish and Wildlife, September 1,
2000.
Rogers, R., Washington Department ofFish and Wildlife. Personal
communication, January - August, 2001.
Rogers, R. (2001a). The green menace: the European green crab. Environmental
Practice 3(2):93-95.
Rogers, R. (2001b). Alien invader: the European green crab. Presentation given
at Nisqually Wildlife Refuge, WA, on August 29, 2001.
Sato, C., Washington Department ofFish and Wildlife. Personal communication,
August, 2001.
Say, T. (1817). An account ofthe Crustacea ofthe United States. Journal,
Academy ofNatural Sciences ofPhiladelphia 1:57-63.

99

Schmid, R. (2001). El Nifio might return. The Olympian, September 8, 2001.
<http://news. theolympian.com/stories/200 10908/HomePageStories/
102667 .shtml>
Schoener, A., and D. L. Fluharty (1985). Biological anomalies offWashington in
1982-83 and other major Nifio periods. In El Nino North: Nino Effects in the
Eastern Subarctic Pacific Ocean. W. S. Wooster and D. L. Fluharty, eds.
Washington Sea Grant Program, University ofWashington, Seattle, pp. 211-225.
Sea Grant Oregon (2000). Draft summary report, Green Crab 2000 Workshop.
Seattle, WA, held March 23,2000.
Sheldon, I. (1998). Seashore of the Pacific Northwest. Vancouver (BC): Lone
Pine Publishing.
Singh, R. (1991). Natural diet of, and shelter-use by, the green crab, Carcinus
maenas{L.) (Nova Scotia). M.Sc. Thesis, The University ofNew Brunswick
(Canada).
Smith, S., Washington Department ofFish and Wildlife, Aquatic Nuisance
Species Division. Personal communication, May, 2001.
Thompson, A. B. {1985). Transmission dynamics of Profilicollis botulus
(Acanthocephala) from crabs (Carcinus maenas) to eider ducks (Somateria
mollissima) on the Ythan Estuary, N.E. Scotland. Journal ofAnimal Ecology
54(2):605-616.
Thresher, R. E. (1997). Proceedings of the first international workshop on the
demography, impacts and management of introduced populations of the European
crab, Carcinus maenas: 20-21 March 1997. Centre for Research on Introduced
Marine Pests, Hobart, Tasmania, Australia. Technical Report 11.
Torchin, M. E., K. D. Lafferty, and A.M. Kuris (1996). Infestationofan
introduced host, the European green crab, Carcinus maenas, by a symbiotic
nemertean egg predator, Carcinonemertes epialti. Journal of Parasitology
82:449-453.
USEP A (1999). Office of Pesticide Programs list of chemicals evaluated for
carcinogenic potential. United States Environmental Protection Agency,
Washington, D.C.
University of Victoria {2000). Sustainable seafood in a changing climate.
Workshop report, May 25-26,2000. <http://www.cics.uvic.ca/workshop/
FinalReport.htm>
100

University of Washington (1999-2001). Non-indigenous species facts: green
crab. University Libraries Information Gateway, <http://www.wsg.washington.
edu/outreachlmas/aquaculture/crab.html>

I
''

l

Walton, W. C. (1997a). Attempts at physical control of Carcinus maenas within
coastal ponds of Martha's Vineyard, MA (northeastern coast ofNorth America).
Proceedings of the first international workshop on the demography, impacts and
management of introduced populations of the European crab, Carcinus maenas:
20-21 March 1997. Centre for Research on Introduced Marine Pests, Hobart,
Tasmania, Australia. Technical Report 11.
Walton, W. C. (1997b). Preliminary evaluation ofthe impact of Carcinus maenas
upon the native Tasmanian clam (Katelysia scalarina) fishery. Proceedings of the
first international workshop on the demography, impacts and management of
introduced populations of the European crab, Carcinus maenas: 20-21 March
1997. Centre for Research on Introduced Marine Pests, Hobart, Tasmania,
Australia. Technical Report 11.
Walton, W. C., Smithsonian Environmental Research. Personal communication,
April, 2001.
Washington Department ofFish and Wildlife (1995). Management
Recommendations for Washington's Priority Species, Vol. 1: Invertebrates. E. M.
Larson, E. Rodrick, and R. Milner, eds. Olympia (WA).
Washington Department ofFish and Wildlife (1998-2000a). Grays Harbor catch
data. Washington Department ofFish and Wildlife, Nahcotta, WA field station.
Washington Department ofFish and Wildlife (1998-2000b). Willapa Bay catch
data. Washington Department ofFish and Wildlife, Nahcotta, WA field station.
Washington Department ofFish and Wildlife (1999a). Priority Habitats and
Species List. July, 1999.
Washington Department ofFish and Wildlife (1999b). Recommendation
summary. <http://www.ofm.wa.gov/budget99/recsum/477rs.htm>
Washington Department ofFish and Wildlife (1999c). Zebra Mussel and
European Green Crab Task Force Report and Recommendations. <http://
www.wa.gov/wdfw/fishlnuisance/zmegct£htm>
Washington Department ofFish and Wildlife (1999d). First person: an interview
with Brett Dumbauld, Research Scientist. <http://www.wa.gov/wdfw/pubaffrs/
1stpersn/dumbauld.htm>
101

'l
~

I

j

l

I
I

I

lI

Washington Department ofFish and Wildlife (1999e). Green crab monitoring
groups. Map obtained from C. Sato, Washington Department ofFish and
Wildlife, Brinnon, WA.
Washington Department ofFish and Wildlife (2000a). State Candidate species.
Revised June 21, 2000.
Washington Department ofFish and Wildlife (2000b). New ballast water rules in
effect. <http://www. wa.gov/wdfw/fish/nuisance/ballast.htm>
Washington Department ofFish and Wildlife (2001a). Aquatic nuisance species:
European green crab. <http://www.wa.gov/wdfw/fish/ans/greencrb.htm>

;

Washington Department ofFish and Wildlife (2001b). Washington Department
of Fish and Wildlife green crab survey effort. Map obtained from R. FiglarBames, Washington Department ofFish and Wildlife, Nahcotta, WA.
Washington Department ofFish and Wildlife (2001-02). Fishing in Washington:
Sport Fishing Rules.
Washington State Aquatic Nuisance Species Committee (1998). Washington
State Aquatic Nuisance Species Management Plan. State of Washington, June
1998. Updated April, 2001.
Welch, W. R. (1968). Changes in abundance of the green crab, Carcinus maenas
(L.), in relation to recent temperature changes. Fishery Bulletin 67:337-345.
Wiegardt, L., Jolly Roger Oysters - Wiegardt Bros., Inc., Nahcotta, W A. Personal
communication, April, 2001.
Wilcove, D., M. J. Bean, R. Bonnie, and M. McMillan (1996). Rebuilding the
ark: toward a more effective Endangered Species Act for private land.
Washington (DC): Environmental Defense Fund. Also available at <http://
www .edf.org/pubs/Reports/help-esa/index.html>.
Wilcove, D. S., D. Rothstein, J. Dubow, A. Phillips, and E. Losos (1998).
Quantifying threats to imperiled species in the United States. BioScience
48(8):607-615.
Wilhelm, S. (2000). Exotic invasion. Puget Sound Business Journal, October 6,
2000. <http://seattle.bcentral.com/seattle/stories/2000/1 0/09/focusl.html>
Wilson, E. 0. (1992). The Diversity ofLife. Cambridge (MA): Belknap Press.