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Identifying Effective Sperm Whale (Physeter macrocephalus)
Depredation Deterrent Strategies for Washington Coast Commercial
Longline Fishermen
by
Scott Mazzone
A Thesis
Submitted in partial fulfillment
of the requirements for the degree
Master of Environmental Studies
The Evergreen State College
June 2013
© 2013 by Scott Mazzone. All rights reserved.
This Thesis for the Master of Environmental Studies Degree
by
Scott Mazzone
has been approved for
The Evergreen State College
By
________________________
Ralph Murphy Ph.D.
Member of the Faculty
________________________
Date
ABSTRACT
Identifying Effective Sperm Whale (Physeter macrocephalus) Depredation Deterrent
Strategies for Washington Coast Commercial Longline Fishermen
Scott Mazzone
Depredation is defined as marine mammals interacting with fishing gear for the
purpose of obtaining caught fish. This problem is found in oceans worldwide
(Symposium 2006, McPherson et. al. 2010). Sperm whales (Physeter macrocephalus)
have been documented depredating the Alaskan longline fishery starting in the late 1970s
and continuing into the present day with no sign of stopping (Hill et. al. 1999). As
recently as 2008, fishing vessels off of the Washington coast have reported sperm whale
interactions. This thesis will examine sperm whales in general, the effects of depredation
on both the whales and fishermen, important scientific findings, avoidance strategies, and
the search for effective deterrents. Numerous deterrent strategies have been employed
over the years with mixed results. By examining what works, what doesn't work, and
what is currently being tested, the author will provide Washington coast fishermen and
fisheries managers with a list of available options for economically and effectively
dealing with sperm whale depredation.
Table of Contents
Depredation…………………………………………………..….…..……. ……...Page 1
Sperm Whales……………………………………………...……….....…………...Page 2
Longline Fishing Operation……………………...………………...….…………...Page 6
Economic loss………………………………………………..………………….…Page 8
Effects on Stock Assessment……………………………......…………..…………Page 11
Important Research Findings………………………………………………………Page 13
Deterrent Methods and Effectiveness………………………………...……………Page 24
Acoustical Deterrents………………………………………………………Page 24
Dummy Sets…………………………………………………..……………Page 25
Group Hauls…………………………………………..……………………Page 26
Circle Haul………………………………………………...……………….Page 27
Hydrophone………………………………………………….…………….Page 27
Shorter Longlines……………………………………………..……………Page 28
Night Hauling……………………………………………………................Page 29
Echosounder………………………………………………………………..Page 29
Avoiding Whale Hotspots…………………………………...……………..Page 29
Firearms…………………………………………………………………....Page 30
Eliminating Offal Discharge……………………………………………….Page 30
Streamer Devices…………………………………………………….…….Page 31
Leaving the Area While Gear is Soaking…………………………………..Page 32
Deterrents Currently Under Development………………………………..………..Page 33
Acrylic Beads…………………………………………………………..…..Page 33
iv
Bubbler………………………………………………………..……………Page 34
Decoy Playback Experiments……………………………..……………….Page 36
Conclusion……………………………………………………………...………….Page 37
Future Research Needs and Discussion……………………………...…………….Page 39
Identifying the Scope………………………………………………………Page 39
Sperm Whale/Longline Interaction Logbook………………………………Page 40
Educating Fishermen……………………………………………………….Page 43
Sperm Whale Identification and Documentation…………….…………….Page 48
Fishermen on the Front Line……………………………………………….Page 50
References Cited………………………………………………………...…………Page 52
Bibliography………………………………………………………………………..Page 58
v
List of Figures
Figure 1 – The sperm whale…………………………………………....…………..Page 3
Figure 2 – Longline operation…………………………………………...………....Page 6
Figure 3 – Halibut setline survey locations………………………………...............Page 12
Figure 4 – Acoustic hydrophone deployment……………………………...............Page 15
Figure 5 – Acoustical hydrophone data during a depredation event……………….Page 17
Figure 6 – Video documentation experiment layout……………………………….Page 21
vi
List of Tables
Table 1 – Alaskan/Washington Longline Fleet Comparison………….…....……...Page 8
Table 2 - Potential Economic Loss in the WA Coast Halibut Fishery from
Depredation……………………………………………………..…………...…......Page 10
Table 3 - Potential Economic Loss in the WA Coast Blackcod Fishery from
Depredation…………………………………………………………………….......Page 11
Figure 4 - Sperm Whale/Longline Interaction Logbook……………………….…..Page 42
Figure 5 – Educational Handout on Depredation Strategies for Fishermen……….Page 44
vii
List of Pictures
Picture 1 – Entangled sperm whale………………………………………………..Page 1
Picture 2 – Sperm whale fishing vessel interaction……………………………….Page 5
Picture 3 – Sperm whale tagging…………………………………………………..Page 18
Picture 4 – Still shots of sperm whale depredation…………………..…………….Page 22
Picture 5 – Remains of a halibut after sperm whale depredation………………….Page 23
Picture 6 – Streamer lines……………………………………………...…………..Page 31
Picture 7 – Acrylic beads on a longline………………………………...………….Page 34
Picture 8 – A bubbler device currently in development…………………...............Page 36
Picture 9 – Pictures of individual sperm whale flukes…………………………..…Page 50
viii
Acknowledgements
A special thanks
to the following organizations for their assistance,
knowledge, information, and support.
Quinault Indian Nation
Quinault Tribal Longline Fishermen
Quinault Tribal Enterprises
Washington Department of Fish and Wildlife
Alaskan Longline Fishermen’s Association
Alaska Department of Fish and Game
University of Alaska Southeast
The Evergreen State College
NOAA Fisheries
North Pacific Research Board
International Pacific Halibut Commission
Northwest Indian Fisheries Commission
Cascadia Research Collective
Scripps Institute of Oceanography
Southeast Alaskan Sperm Whale Avoidance Project
And a special thanks to Ralph Murphy Ph.D.
ix
Depredation
Depredation is defined as the interaction of marine mammals with fishing gear to
obtain caught fish (Gilman et. al. 2006). This problem has been documented worldwide
in a variety of different fisheries (Donoghue et. al. 2003, Hamer et. al. 2010, McPherson
Per. Com 2012, O'Connell Per. Com 2012). Longline fisheries and driftnet fisheries are
most susceptible to this phenomenon because marine mammals are attracted to the
fishing gear by the lure of easily obtained food (Donoghue et. al. 2003). As a result,
marine mammals risk the danger of becoming entangled in the fishing gear, causing their
injury or death (Hamer et. al. 2010).
Picture 1 – Entangled sperm whale
A sperm whale entangled in a driftnet. Courtesy of Tumblr.com http://speciesendangered.tumblr.com/
1
Depredation also causes marine mammals to deviate from their natural feeding behavior
and potentially consume an otherwise unobtainable food source. Fish that under normal
conditions could avoid marine mammals are easy prey when hooked or entangled in
fishing gear. This added food source could lead to an abnormal increase in marine
mammal populations, which normally would not be sustainable under normal foraging
behavior (Straley Per. Com 2012).
In addition, fishermen may also harass marine
mammals in an effort to protect their catch, also potentially causing injury or death to the
marine mammals (Hamer et. al. 2010).
Sperm Whales
This thesis addresses sperm whale depredation in the Northeastern Pacific Ocean,
specifically in waters off of the Washington outer coast. By the time the International
Whaling Commission (IWC) banned commercial whaling in 1986, sperm whales had
been hunted almost to the point of extinction (Calambokidis Per. Com 2012). Even today,
they are listed as an endangered species. Their exact population size is unknown but is
estimated to be in the low hundred thousands, well below their pre-whaling numbers,
which were estimated at over one million worldwide (Calambokidis Per. Com 2012).
Females and calves in the eastern Pacific Ocean typically forage off the southern
California/Mexican coast, utilizing the warm water conditions (Christal et. al. 2001). By
contrast, adult males in the eastern Pacific Ocean migrate up the U.S. Pacific coast into
Alaskan waters to highly productive feeding grounds. There, the males remain for years
living mostly a solitary life, although they have been known to form loose groups
(Calambokidis Per. Com 2012, Christal et. al. 2001). These males are the cause of sperm
2
whale depredation occurring to the longline fleets from Washington State up into Alaska
waters.
Figure 1 – The sperm whale
The sperm whale (Physeter macrocephalus). Image by Uko Gorter Natural History
Illustrations. Courtesy of The Marine Detective. http://themarinedetective.com/tag/whale/
To date, the vast majority of sperm whale depredation is occurring in Alaskan
waters with only intermittent reports of fishermen/whale interactions off the Washington
coast. This has the potential to change in the coming years as the sperm whale
populations continue to grow and to learn depredation behavior from older whales
(Straley Per. Com 2012). Sperm whales are the largest of the toothed whales, with adult
males reaching around sixty feet in length and weighing in excess of fifty tons
(Calambokidis Per. Com 2012, Christal et. al. 2001). They typically feed along the
3
continental shelf and forage dive to average depths of 400 to 500 meters, preying on
squid and fish (Mathias et. al. 2009). Normal sperm whale foraging dives last an average
of 30 to 35 minutes (Thode et. al. 2006). Sometime in the late 1970s, sperm whales
slowly lost their fear of ships, which stemmed from earlier whaling days, and began, to
associate boats with food. Vessels no longer meant death to the whales but instead
became a source of easily obtained food (Straley Per. Com 2012).
In 1985, because of an increasing trend of whale interactions and lost catch, some
Alaskan longline fishermen began documenting sperm whale interactions and have
observed that the problem has gotten progressively worse over time (Straley Per. Com
2012, O'Connell Per. Com 2012). This can be attributed to the increase in sperm whale
populations (Calambokidis Per. Com 2012) and to the lack of commercial whaling. In
addition, in 1995 Alaska implemented Individual Fishing Quotas (IFQ) into their longline
fisheries (Straley et. al. 2011). Instead of a derby style fishery only lasting a couple of
weeks each year, fishermen now have an individual quota, which means they can fish at
any time they choose. This has led to a season lasting up to eight months each year and
has provided a much greater opportunity for sperm whales to prey on caught fish (Straley
et. al. 2011). Based on these trends and changes to the fisheries, the cases of sperm whale
depredation are expected to increase and the problem area to expand.
4
Picture 2 – Sperm whale fishing vessel interaction
A photograph of a sperm whale following a longline fishing vessel. Courtesy Southeast
Alaska Sperm Whale Avoidance Project (SEASWAP). Photo by Heather Vukelic.
http://www.seaswap.info/background/index.html
Perhaps more importantly, this problem is spreading. As this is a learned
behavior, the adult males teach the younger males how to depredate (Straley Per. Com
2012). Beginning in 2008-2009 and continuing each year to the present day, Quinault
tribal longline fishermen off the outer coast of Washington have also begun reporting
incidents of sperm whale depredation in their blackcod (Anoplopoma fimbria) and halibut
(Hippoglossus stenolepis) longline fisheries (Charley Per. Com 2008, Frank Per. Com
2013, Rhoads Per. Com 2013). These initial reports from the fishermen themselves have
led to the investigation of this phenomenon in Washington waters and the conception of
5
this thesis. Without the direct interaction between fishermen and fisheries managers, this
emerging problem could have gone unnoticed for years. As depredation is a learned
behavior (Straley Per. Com 2012), it is vital for fishermen and researchers to work
together to find a solution along the Washington coast before it becomes as big an issue
as it is in Alaska.
Longline Fishing Operation
A typical longline operation consists of a fishing vessel steaming out to the
fishing grounds and dropping an anchor with a buoy line attached (the buoy marks one
end of the fishing gear at the surface).
Figure 2 – Longline Operation
A diagram of a typical longline operation. Courtesy of Southeast Alaska Sperm Whale
Avoidance Project (SEASWAP). http://www.seaswap.info/background/longlining.html
6
A separate line is also attached to the anchor. This “longline” is then laid out on the sea
floor. “Gangions” or small lengths of line attached to the longline at intervals of three to
six feet have hooks and bait attached at the opposite end. Longlines can sometimes
stretch for miles, but off the Washington coast, they are typically an average of 1,800 feet
in length (Charley Per. Com 2008, Frank Per. Com 2013, Rhoads Per. Com 2013). At the
opposite end of the longline, another attached anchor secures the gear to the bottom, and
another line and buoy mark the location on the surface. This entire setup is called a
“skate” or “set” and a Washington coast fisherman will typically fish with an average of
four to six sets at a time but this can vary from vessel to vessel (Charley Per. Com 2008,
Frank Per. Com 2013, Rhoads Per. Com 2013).
The skates are left on the ocean floor between one and four hours to “fish” (soak
time). Then the fisherman retrieves the longline, hauling it back on board by winding it
around a steel drum, which uses the ship hydraulics to rotate. Fish are removed from the
hooks as they come aboard, and the gear is readied for the next set. Depending on which
species of fish the fishermen are targeting, they will adjust their set locations to habitat
types and known “hot spots” frequented by their target species (Charley Per. Com 2008,
Frank Per. Com 2013, Rhoads Per. Com 2013).
The greatest density of fish populations lie in Alaskan waters, therefore, the
majority of longline fishing takes place in Alaskan waters. To illustrate this point the
International Pacific Halibut Commission (IPHC) scientists estimate 94% of the Pacific
Halibut reside in Alaskan waters, 5% of the Pacific Halibut live in Canadian waters, and
the remaining 1% of the Pacific Halibut live in Washington/Oregon/California waters
(Webster et. al. 2013). Compared to the Alaskan fisheries, Washington has far fewer
7
boats fishing on a much smaller fish population and therefore, any loss to sperm whales is
noticeable. This distribution also demonstrates why sperm whale depredation is a greater
issue in Alaska; that is where the majority of fish are concentrated (Straley Per. Com
2012, Dykstra Per. Com 2012, Peterson Per. Com 2012, O’Connell Per. Com 2012).
Table 1 – Alaskan/Washington Longline Fleet Comparison
Alaksan/Washington Fleet Comparison
WA Tribal
WA State
Total WA
AK LongLine
Registered
Registered
Registered
Registered
Longline Fishing Longline Fishing
Longline
Fishing
Vessels
Vessels
Fishing Vessels
Vessels
Year
2010
158
59
217
2872
2011
168
67
235
2826
2012
209
58
267
2767
2013
208
N/A
N/A
1645
Table 1 compares the sizes of Alaskan and Washington tribal and non-tribal fleets from
2010 through 2013. It should be noted that the majority of the tribal fleet fish inside the
Strait of Juan de Fuca and North Puget Sound. Only about 40 tribal boats fish the outer
coast where sperm whale depredation has been reported. It should also be noted that
registered fishing vessels does not necessarily mean they are actively fishing. The above
data was obtained from Alaska Department of Fish and Game (ADFG), Washington
Department of Fish and Wildlife (WDFW), and the Northwest Indian Fisheries
Commission (NWIFC)
Economic Loss
The fishermen suffer the effects of depredation from loss of catch (income) and a
potential loss of or damaged gear (investment) (Straley Per. Com 2012). Depending on
the percent of lost catch, the economic impact can be staggering. During the 2013
8
Washington coast longline season, fishermen made an average of $5.40 a pound for
halibut (Hippoglossus stenolepis) and an average of $3.50 a pound for blackcod
(Anoplopoma fimbria) (prices obtained from Quinault Tribal Enterprises (QTE))
(Heathers Per. Com 2013); a 5% to 10% loss from depredation can equate to substantial
loss of revenue (see tables 2 and 3 on the following pages).
At present, there are only intermittent reports of sperm whale depredation off the
Washington outer coast and no reports of depredation occurring in the Strait of Juan de
Fuca or North Puget Sound according to Tribal and state managers. If the problem is
simply tolerated or ignored, there is real potential for depredation to occur more
frequently and over a larger area. The fishermen are the ones that brought attention to the
problem and they also must be a part of the solution. This lesson can be learned from
looking at Alaska. The Alaskan Longline Fishermen’s Association (ALFA) has partnered
with scientists from the Southeast Alaska Sperm Whale Avoidance Project (SEASWAP)
in an effort to work together to find an effective deterrent (Straley et. al. 2011). The
fishermen report whale interactions and offer possible solutions based on their
knowledge. SEASWAP develops deterrent strategies based on the fishermen’s input and
known scientific research, and employs the fishermen to test these strategies and report
the results (Straley et. al. 2011).
The potential economic loss in the following figures should convince most
fishermen of the need for action. A Washington coast fisherman will have to spend more
on fuel, more on bait, and stay out longer to bring in the same amount of fish if a sperm
whale is depredating his or her lines during each haul.
9
Table 2 - Potential Economic Loss in the WA Coast Halibut Fishery from
Depredation
Washington Coast Halibut Fishery
Total Allowable
Catch in Pounds
Average Price Paid
Per Pound
Total Financial
Value
1% Financial
loss From
Depredation
5% Financial
Loss From
Depredation
10% Financial
Loss From
Depredation
2010
Tribal Commercial
253,072
$4.75
$1,202,092.00
$12,020.92
$60,104.60
$120,209.20
State Commercial
141,865
$4.75
$673,858.75
$6,738.59
$33,692.94
$67,385.88
2011
Tribal Commercial
293,200
$5.00
$1,466,000.00
$14,660.00
$73,300.00
$146,600.00
State Commercial
159,380
$5.00
$796,900.00
$7,969.00
$39,845.00
$79,690.00
2012
Tribal Commercial
321,650
$6.25
$2,010,312.50
$20,103.13
$100,515.63
$201,031.25
State Commercial
173,216
$6.25
$1,082,600.00
$10,826.00
$54,130.00
$108,260.00
2013
Tribal Commercial
314,300
$5.40
$1,697,220.00
$16,972.20
$84,861.00
$169,722.00
State Commercial
173,391
$5.40
$936,311.40
$9,363.11
$46,815.57
$93,631.14
It is speculated that sperm whales in Alaska are depredating up to 10% of the catch. By
looking at halibut catch limits for WA from 2010 through 2013, the price paid per pound,
the total financial value, 1% loss, 5% loss, and 10% loss, it quickly becomes clear why it
is important to deter depredation and prevent the behavior becoming established along
the Washington outer coast. The economic loss can be quite large. Note that about half of
the tribal total allowable catch (TAC) is caught within the Strait of Juan de Fuca and
North Puget Sound where there have been no reports yet of sperm whale depredation,
however that could change in the future. The above data was obtained from Washington
Department of Fish and Wildlife (WDFW), the Northwest Indian Fisheries Commission
(NWIFC), and Quinault Tribal Enterprises (QTE).
10
Table 3 - Potential Economic Loss in the WA Coast Blackcod Fishery from
Depredation
Washington Coast Blackcod Fishery
Total Allowable
Catch in Pounds
2010
Tribal Commercial
State Commercial
2011
Tribal Commercial
State Commercial
2012
Tribal Commercial
State Commercial
2013
Tribal Commercial
State Commercial
Average Price Paid
Per Pound
Total Financial
Value
1% Financial
loss From
Depredation
5% Financial
Loss From
Depredation
10% Financial
Loss From
Depredation
887,706
$5.40
$4,793,612.40
$47,936.12
$239,680.62
$479,361.24
1,441,706
$5.40
$7,785,212.40
$77,852.12
$389,260.62
$778,521.24
748,186
$6.25
$4,676,162.50
$46,761.63
$233,808.13
$467,616.25
1,429,522
$6.25
$8,934,512.50
$89,345.13
$446,725.63
$893,451.25
726,140
$3.50
$2,541,490.00
$25,414.90
$127,074.50
$254,149.00
1,006,100
$3.50
$3,521,350.00
$35,213.50
$176,067.50
$352,135.00
544,261
$3.50
$1,904,913.50
$19,049.14
$95,245.68
$190,491.35
N/A
N/A
N/A
N/A
N/A
N/A
It is speculated that sperm whales in Alaska are depredating up to 10% of the catch. By
looking at blackcod catch limits for WA from 2010 through 2013, the price paid per
pound, the total financial value, 1% loss, 5% loss, and 10% loss, it quickly becomes clear
why it is important to deter depredation and prevent the behavior becoming established
along the Washington outer coast. The economic loss can be quite large. The above data
was obtained from Washington Department of Fish and Wildlife (WDFW), the
Northwest Indian Fisheries Commission (NWIFC), and Quinault Tribal Enterprises
(QTE). State commercial data for 2013 was not yet available at the time of publication.
Effects on Stock Assessment
Fisheries managers also potentially suffer from the effects of marine mammal
depredation. Fish losses from sperm whale depredation during stock assessment surveys
and during the actual fishery are not directly accounted for (Symposium 2006, Dykstra
Per. Com 2012). Thus, fisheries managers run the risk of overestimating a stock in which
depredation occurs, potentially leading to declining populations and an unsustainable
11
harvest rate. In other words, each year fisheries stock managers attempt to assess specific
species populations through the use of setline surveys and other collected data.
Figure 3 – Halibut Setline Survey Locations
The small dots indicate the locations of the International Pacific Halibut Commission’s
(IPHC) annual setline surveys used to estimate the annual halibut population size and
from that information, set the yearly sustainable harvest limits. Courtesy of the
International Pacific Halibut Commission. http://www.iphc.int/home.html
Longline sets are placed in predetermined spots throughout the species range and the
obtained catch is recorded (Dykstra Per. Com 2012). Scientists can then estimate the
entire population based on number of fish caught in these survey sets and other data
collected by extrapolating the numbers. Catch limits are then derived for the upcoming
season (Dykstra Per. Com 2012). Fishermen were concerned that fish lost by depredation,
either in the set line surveys or during the actual commercial fishery, were not being
accounted for and therefore, scientists did not have an accurate understanding of the
12
stock. The International Pacific Halibut Commission (IPHC) addressed these concerns in
their 2010 RARA research publication;
Commercial fishers often express concern over how the impacts of
depredation are interpreted by the IPHC, both from their fishing logs and
from the stock assessment survey. Of particular concern to harvesters is
the perception that the mortality resulting from depredation in the
commercial fishery is not accounted for by assessment scientists. While
this perception is widespread, it is incorrect. Any mortality on halibut will
be apparent in the stock assessment because the mortality affects numbers
of fish at each age, which the assessment is designed to estimate.
However, it is certainly true that the assessment will not be able to
differentiate depredation mortality from other sources of mortality in the
same areas. In this sense, the assessment will accurately account for
depredation mortality but will not necessarily assign it to the correct
source. The mortality should correctly be assigned as fishing mortality
because the fish were already on the hook when depredated.
Managers also struggle to understand when and how to screen survey data
that may have suffered depredation interference. Agencies generally have
some pre-established screening methods for determining when data are
acceptable for inclusion in stock assessment analysis. Currently, the
IPHC deems a station to be effective when the data obtained from that set
can be used in the stock assessment analysis. If the gear did not fish
properly, or the catch is not representative of what might have been caught
under normal circumstances, the station is rated ineffective. For a set to
be defined as ineffective due to whale depredation, there must be whales
present in the area during haul back and the sum of damaged gear and
damaged catch must be greater than 10% of the hooks set. This threshold
is somewhat arbitrary, and more years of depredation data will help us
refine this threshold.
-
Dykstra, C. L., and Eric Soderlund. 2010. Categorizing marine
mammal depredation on IPHC standardized setline surveys. IPHC
Report
of
Assessment
and
Research
Activities
2010.
http://www.iphc.int/publications/rara/2010/2010.435.Categorizingmari
nemammaldepredationonIPHC.pdf
Important Research Findings
As the problem of sperm whale depredation grew progressively worse in Alaska,
the Alaskan Longline Fishermen's Association (ALFA) called for action from the
13
scientific community to investigate solutions, as they were no longer willing to accept the
rate of lost catch without attempting to identify solutions. At the rate of their lost income,
a major concern was that it would no longer be economically profitable to continue
fishing.
The Southeast Alaskan Sperm Whale Avoidance Project (SEASWAP) was
formed in 2003 to research sperm whale depredation behavior and to identify mitigation
strategies fishermen could employ to limit or eliminate whale interactions (Thode et. al.
2008, Straley et. al. 2011, Straley Per. Com 2012). One of the first items SEASWAP
wanted to quantify was how whales were able to identify fishing vessels that were
engaged in longline retrieval (hauling their catch aboard), as opposed to normal vessel
activity. If this “Pavlov’s bell” could be identified, stopping depredation might be as
simple as removing the signal the whales were homing in on (Thode et. al. 2008, Straley
et. al. 2011, Straley Per. Com 2012).
It had been observed by fishermen that sperm whales tended to keep their distance
from ships until the vessel began retrieving their longline and catch (Dykstra Per. Com
2012). It was speculated that the whales heard the hydraulics being engaged (used to
recover the longline) through the water and zeroed in on the ship (Thode et. al. 2007,
McPherson 2011, Dykstra Per. Com 2012). Utilizing the help of Alaskan longline
fishermen, SEASWAP set up an experiment. By lowering hydrophones (underwater
microphones) into the water and then listening as another ship in close proximity engaged
and disengaged their hydraulics, researchers learned that the sound was barely audible
and was therefore, not the clue the whales were responding to (Thode et. al. 2007,
McPherson 2011, Dykstra Per. Com 2012).
14
Figure 4 – Acoustic Hydrophone Deployment
A diagram illustrating the deployment of an acoustic hydrophone for the purpose of
recording sperm whales and ship noise. Courtesy of NOAA Ocean Explorer
Technologies for Ocean Acoustic Monitoring
http://oceanexplorer.noaa.gov/technology/tools/acoustics/acoustics.html
After eliminating this theory, hydrophones were again used in subsequent testing
around an active fishing vessel with surprising results. The tests showed that as a fishing
vessel retrieves its longline gear, the captain has to constantly switch the vessel in and out
of gear to keep the ship directly over the longline. Each time the prop is reengaged,
cavitation (bubbles produced from the prop spinning) occurs. This distinct sound could
be heard by sperm whales more than five kilometers away (Dykstra Per. Com 2012,
McPherson 2011, Thode et. al. 2007, Straley Per. Com 2012). In fact, because each boat
15
has a different size prop and therefore makes its own distinct sound, the whales could
actually recognize individual vessels and target boats that typically brought in larger
catches (Dykstra Per. Com 2012).
To test their findings, researchers had a boat captain steam several miles away
from a set of active fishing gear. The captain then shifted his boat in and out of gear
mimicking longline retrieval behavior. Sperm whales were sighted in the area within five
minutes, thus confirming the results (Dykstra Per. Com 2012, McPherson 2011, Thode et.
al. 2007, Straley Per. Com 2012). The captain was able to “summon” whales by simply
using his ship’s prop to cause cavitation and produce sound. This single finding identified
the acoustical signal that whales equated to an easily acquired source of food and that
attracted them to the fishing vessels.
16
Figure 5 – Acoustical Hydrophone Data Dduring a Depredation Event
This graph was created from acoustical hydrophone data gathered on May 9, 2004. The
ship’s hydraulics were engaged when the anchor line was grappled (9:07 AM), but the
whales did not react until 9:27 AM when the ship began cycling in and out of gear. This
is clear evidence the whales are attracted to the sound of prop cavitation and not to the
sound of ship’s hydraulics. Courtesy of Thode et. al. 2006.
http://doc.nprb.org/web/04_prjs/f0412_final_report.pdf
Next, SEASWAP, with the Acoustical Society of America, wanted to document
normal sperm whale foraging behavior and compare it to depredation behavior. To
accomplish this, passive acoustic recordings of sperm whale “clicks” (the sounds sperm
whales make that aids them in echolocation) were collected from hydrophones deployed
from small boats and fishing gear and an acoustic multi-path was used which can derive
17
the range and depths of the target animal. In addition, depth-recording tags were attached
to eight animals, providing 80 hours of dive profile data (Thode et. al. 2009).
Picture 3 – Sperm Whale Tagging
A researcher preparing to affix a suction cup recording tag to a whale. These tags will
typically remain affixed to the whale for up to 48 hours. Courtesy of Discovery of Sound
in the Sea http://www.dosits.org/
Recordings were made both while whales were foraging naturally and when they
were observed actively depredating longline gear during retrieval. The results between
the two different types of feeding behavior were distinct (Thode et. al. 2009, Straley Per.
Com 2012). During normal foraging, whales dove to depths of 200 to 400 meters and
stayed submerged for an average of 29 minutes (Sigler et. al. 2008, Mathias et. al. 2009,
Mathias et. al. 2012). By contrast, depredating whales dove to less than 100 meters and
stayed submerged an average of five minutes per dive (Thode et. al. 2009, Mathias et. al.
18
2012). During depredation, the longlines with caught fish attached are being hauled to the
surface; therefore, there is no need for the whales to make deep dives for extensive
periods of time. They just stay close to the boat and fishing gear, and surface frequently.
Much less energy is expended because there is no need to chase after their prey.
Sperm whales produce clicks to help in echolocation of food (Mathias et. al. 2009,
Miller et. al. 2004). When they are actively foraging, their normal rate of clicks increases
to 10 per second or greater (Wild Per. Com 2012, Miller et. al. 2004). These increased
rates of clicks help the sperm whale target and locate its prey (Straley Per. Com 2012,
Miller et. al. 2004). In addition, it is speculated that in some marine mammal species,
including the sperm whale, the increased rate of clicks might actually stun the prey fish,
making acquisition even easier for the whales (Calambokidis Per. Com 2012). This
acoustic activity is called a “creak” (Mathias et. al. 2009, O'Connell Per. Com 2012,
Straley Per. Com 2012). Creaks, followed by a period of silence, indicate a prey capture
event (Thode et. al. 2009, Straley Per. Com 2012, Miller et. al. 2004).
During depredation, scientists using acoustical hydrophones recorded a creak rate
twice that of a normal foraging sperm whale (Thode et. al. 2009, Miller et. al. 2004).
From this study, it is clear that depredation is not a normal foraging activity for sperm
whales. The difference between dive depth and duration is significant (Thode et. al.
2009). In addition, based on the creak data obtained, it would appear that sperm whales
are twice as effective at acquiring prey from depredation as during normal foraging
(Miller et. al. 2004). In one case, a tagged sperm whale stopped producing creaks for five
hours after a depredation event, possibly indicating just how effective foraging off a
longline is (as there is no need to forage for an extended period of time) (Thode et. al.
19
2009). Because of this, sperm whales are unlikely to stop depredation on their own;
rather, this activity will continue to increase over time unless an effective deterrent is
identified (Symposium 2006).
Another breakthrough finding occurred in 2006. SEASWAP, working with
researchers from SCRIPPS Institute of Oceanography and commercial fishermen,
attempted to film sperm whale behavior while depredating (Thode et. al. 2009). Scientists
accompanied a fishing vessel actively fishing for blackcod. As the crew prepared to
retrieve its longline gear, hydrophones were lowered into the water to confirm the
presence of sperm whales. A camera was lowered into the water facing the surface (to
utilize ambient light) to a depth of 100 meters (Thode et. al. 2009).
20
Figure 6 – Video Documentation Experiment Layout
A diagram displaying camera placement on a longline used to film sperm whale
depredation. Courtesy of Thode et. al. 2009
http://doc.nprb.org/web/06_prjs/626_final%20report_June09.pdf
Bait fish (in this case, blackcod) were attached to the line above the camera. The resulting
footage clearly shows a sperm whale entering into the field of view, grasping the longline
with its jaw, and “twanging” the longline like a guitar string to dislodge one of the bait
fish (Thode et. al. 2009, Per. Com 2012). As the fish drifts out of camera view, the whale
detaches from the line and swims out of view as well, presumably going after the bait fish
to consume it. This is the first time underwater sperm whale depredation has been caught
on tape.
21
Picture 4 – Still Shots of Sperm Whale Depredation
Still shots of a video filmed by Scripps Institute of Oceanography clearly showing a
sperm whale grabbing a longline in its jaws and shaking loose a blackcod. Courtesy of
Scripps Institute http://scrippsnews.ucsd.edu/Releases/?releaseID=995
What is amazing and groundbreaking about this footage is that the whale never
touches the fish and there was no evidence of the depredation on the hook. Up to this
point, depredation was assumed to have occurred when mangled fish, heads, lips, or bent
hooks were observed on the haul back (Dykstra Per. Com 2012). If the hooks were empty
at haul back, it was assumed that the bait either fell off during the gear set or smaller
scavenger fish ate the bait while the line was on the bottom. Empty hooks were never
before attributed to sperm whale depredation. This footage clearly depicts how whales
can depredate a line and leave behind no evidence of their behavior (Straley Per. Com
2012, O'Connell Per. Com 2012).
The implications of this single finding meant that the amount of depredation
believed to be occurring could have been severely underestimated (it was previously
thought sperm whales were taking only 5% to 10% of the overall catch per set depredated
based just on the evidence left on hooks) (Dykstra et. al. 2010, Hill et. al. 1999). This
22
single finding could have substantial impact on setline data used for population stock
assessments of commercial fish species. Empty hooks recovered from set line surveys
might actually have been caught fish that were preyed upon by sperm whales; potentially
skewing the overall assessment.
Picture 5 – Remains of a Halibut after Sperm Whale Depredation
An Alaskan longline fisherman holds up the remains of a halibut that was depredated by
a sperm whale. Courtesy of Wild Whales B.C. Cetacean Sightings Network. Photo by
Dan Falvey. http://wildwhales.org/conservation/threats/depredation/
23
Deterrent Methods and Effectiveness
The reward to sperm whales is too great for them to stop depredating on their
own, and not taking action to stop this phenomenon is unacceptable to fisherman because
of the loss of their gear and income. Over the years, numerous devices and strategies
have been devised, tested, employed, and discarded in different fisheries throughout the
world. This thesis examines the more popular deterrent methods, rates their effectiveness,
and identifies the most cost-effective and successful methods for Washington coast
longline fishermen to employ in their fishing operations. These recommendations are
based on peer-reviewed scientific studies, advice and recommendations from research
organizations, reports from fishermen, communications with scientists, the success rate of
past and present deterrent strategies, and known fishing grounds and ocean conditions
specific to Washington coast fishermen. The majority of these strategies and devises
come from lessons learned in Alaska. Alaskan fishermen and SEASWAP have been
dealing with this issue for decades and much of their knowledge and experience can be
applied directly to the Washington coast longline fishery.
Acoustical deterrents – The Southeast Alaska Sperm Whale Avoidance Project
(SEASWAP) and their scientists have conducted extensive research into acoustical
deterrents and have published their findings in peer reviewed scientific journals. Overall,
acoustic harassment devices are ineffective as long-term strategies (McPherson 2011,
Symposium 2006). Fishermen have used seal bombs, pingers, recordings of killer whales,
and other sounds with limited success. Sperm whales appear to be initially deterred by
the sounds, but the draw of easy prey and the subsequent acclimation of the whales to the
24
sounds render this strategy ineffective in the long run (Straley Per. Com 2012, Dykstra
Per. Com 2012).
One exception is an approach where a dummy buoy with recordings of a ship
cycling in and out of gear is dropped several miles from the actual fishing gear while the
ship then steams back to the actual fishing gear and hauls it in as fast as possible. This
tactic will work sometimes, but the whales eventually realize they have been fooled at the
dummy buoy and will then show up at the actual fishing spot (Thode et. al. 2008, Thode
et. al. 2007, Straley Per. Com 2012). Ongoing research using a slightly modified method
remotely triggering the playback device will continue in Alaska during the 2013 fishery
(Wild Per. Com 2013).
All these devices however, are a relatively inexpensive investment and can be
very successful in the short-term. For Washington coast fishermen who only encounter
sperm whales on an intermittent basis, this type of deterrent could be quite effective and
should be considered, particularly since it is presently thought that there is no resident
whale population off the Washington coast. (It is presently believed that sperm whales
migrating up the coast to Alaska depredate the Washington fleet as they swim past)
(Straley Per. Com 2012, O'Connell Per. Com 2012, Calambokidis Per. Com 2012). It is
possible, therefore, that these whales could be easily chased off before they become
acclimated to the sounds and simply continue their migration north in search of food.
Dummy Sets – This method is also recommended by SEASWAP based on limited
experimentation and field studies (Straley Per. Com 2012, Thode et. al. 2009). Fishermen
have also dropped dummy sets in an attempt to divert whales from the real set. These
25
decoys are simply an anchor, line, and buoy that look exactly like actual fishing gear. By
dropping these dummy sets several miles from their actual fishing gear, fishermen can
sometimes lure the whales far enough away that they are able to retrieve their gear before
the whales figure out the ruse and show up at the actual fishing gear (O’Connell Per.
Com 2012). This is especially effective if the whales are actually following the vessel
around and if they remain around the dummy set (Thode et. al. 2009). The results of this
method are intermittent at best; in addition, there is the added cost of fuel, gear, and time.
Thus, this is not usually a recommended method. However each fisherman is urged to
weigh the pros and cons and decide for themselves if it is worth it for them.
Group Hauls – This strategy was actually thought up and implemented by Alaskan
fishermen themselves in their own efforts to find a solution (Straley Per. Com 2012).
Occasionally boats will team up and while one hauls in gear, the other boat will be
positioned several miles away, cycling in and out of gear in an attempt to draw the
whales away from the actual fishing vessel.
A similar strategy is that boats fishing in the same area will sometimes coordinate
with each other to simultaneously haul in their gear (Per. Com 2012). This way, any
whales present will be split between all the boats, thus spreading the potential loss of
catch out among all the boats. This method has been employed by Southeast Alaskan
longline fishermen for several years with limited to good success; moreover, the results
are better than doing nothing (Straley Per. Com 2012, O'Connell Per. Com 2012).
It is recommended that this method should also be tried by Washington coast
fishermen because of its low cost and potential success. This method is also made easier
26
because the fishermen tend to be in close proximity of each other on the fishing grounds
(Charley Per. Com 2008, Frank Per. Com 2013, Rhoads Per. Com 2013).
Circle Haul - SEASWAP and the North Pacific Research Board (NPRB) have suggested
a maneuver called a circle haul, where a fisherman steers his boat backwards in a circle
while hauling in the gear in order to stay on top of the line, instead of shifting in and out
of gear (Straley Per. Com 2012, O'Connell Per. Com 2012, Thode et. al. 2009). This way,
there is no cavitation to alert the whales. The drawbacks are that only certain types of
boats can accomplish this maneuver due to their design and the ocean needs to be
relatively flat and calm, which is a rare occurrence in the Northeastern Pacific Ocean
(Straley Per. Com 2012, O'Connell Per. Com 2012).
For Washington coast fishermen, the longline season usually begins in March
(Jones Per. Com 2013), when weather and surf conditions are less than ideal. Under such
conditions, it would be nearly impossible to perform this maneuver. However, depending
on the amount of available fish to be caught each season (total allowable catch or TAC)
and the amount of fishing effort (boats participating), the season can extend into the
summer months, when the ocean conditions are much calmer (Frank Per. Com 2013,
Rhoads Per. Com 2013). It is recommended that if conditions permit and the boat is
capable, this method should be tried. By avoiding cavitation sounds, the whales are less
likely to show up and depredate a fisherman’s catch.
Hydrophone - Fishermen are encouraged to use a hydrophone ($200 - $400) to listen for
whales when preparing to haul in gear (Straley Per. Com 2012, O'Connell Per. Com
2012). This is a standard device used by scientists conducting any type of marine
27
mammal research. A hydrophone will alert the fisherman if whales are present even if
they are submerged and not visible (surfacing) (Straley Per. Com 2012, O'Connell Per.
Com 2012). This added information can assist fishermen in their decision making.
If whales are present, or appear during haul-in, fishermen are encouraged to drop
their gear and/or wait until the whales leave the area before retrieval (Straley Per. Com
2012, O'Connell Per. Com 2012). Fishermen can also maneuver their boats into shallow
water in an attempt to lose a whale. The whale’s echolocation does not work as well in
shallow water as discovered in field studies and observations, so they lose track of the
ship (Straley Per. Com 2012, O'Connell Per. Com 2012, Dykstra Per. Com 2012).
These techniques will cost the fishermen time and money (both in the purchase of
the hydrophone and in the extra gas), so they must weigh the odds and make a decision
which is best for them. If the cost of gas is low and the price paid for blackcod or halibut
is high, this is a beneficial strategy and recommended to Washington coast fishermen.
Shorter Longlines – Another strategy fishermen have implemented themselves is the use
of shorter longlines so they can get their gear on board faster, before the whales appear,
which avoids the depredation entirely. However, the problem with shorter longlines is
that the fishermen need to make more sets (to have the same amount of actively fishing
hooks), which gives the whales more time to find the boat during a haul-in (Straley Per.
Com 2012, O'Connell Per. Com 2012).
As with the use of a hydrophone, each fisherman must determine whether this
strategy is in his or her best interest in the long-term. If whales are already present in the
area, it might make sense to set more hooks so that even though the whales are preying
28
on the catch, the chance of landing more fish increases. In general, this method of shorter
longlines would work best for fishermen with smaller boats (less operating expense and
therefore fewer sets needed to make the trip profitable) (Rhoads Per. Com 2013).
Night Hauling - It was once thought that sperm whales were attracted to fishing boats by
the sea birds that are constantly around during a haul. Alaskan fishermen tried hauling
gear only at night with no success (Thode et. al. 2007). Since it is now known that the
whales are attracted by cavitation and not sea birds (thanks to experiments by Alaskan
commercial fishermen and SEASWAP), this method is completely ineffective.
Echosounder - Another speculation was that the whales would hear the fishing vessel’s
echosounder (an electronic device that depicts current water depth) and thus target the
boat. Experiments from Scripps Institution of Oceanography with commercial fishermen
setting and retrieving gear with the echosounder both on and off showed no statistically
significant difference (Thode et. al. 2007). As with night hauling, since it is now known
that the whales are attracted by cavitation, this method is also completely ineffective and
should not be tried.
Avoiding Whale Hotspots - It has been recommended that fishermen avoid known
sperm whale “hotspots” when setting gear. However whales, like fishermen, know the
areas where the fish are abundant. Sperm whale “hotspots” are usually on prime fishing
ground (Straley et. al. 2005); therefore, this method is undesirable. One exception to this
would be if a fisherman had a smaller vessel and knew an area where fishing was merely
average. Since smaller boats are cheaper to operate and a profit can be made with a
smaller amount of catch (Rhoads Per. Com 2013), it might be desirable to fish in an area
29
with less fish but also no competition from whales. Again, this is a situation where each
fisherman must individually decide what is best for him or her.
Firearms - There have been reports of frustrated fishermen shooting at surfacing sperm
whales with rubber bullets, pepper shot, bullets, and other propellants. Most likely, the
projectiles will not penetrate the blubber layer of the whales, which are several inches
thick (Calambokidis Per. Com 2012). However, if the whale does feel anything, they
likely attribute the pain to surfacing and not feeding, which merely causes them to take
longer dives while continuing to depredate the line (Symposium 2006). More
importantly, this method is in direct violation of the Marine Mammal Protection Act, for
which fishermen face harsh penalties and large fines. No fisherman, no matter how
frustrated, should ever shoot at whales. This method is definitely not recommended.
Eliminate Offal Discharge – Clear documentation (eyewitness reports, photographs,
etc.) exists that shows marine mammals being attracted to vessels discharging offal
(Straley Per. Com 2012, O'Connell Per. Com 2012). Offal is the discarded heads and guts
of cleaned fish and leftover bait. This material is sometime tossed over the side of the
boat, along with any by-catch (non-target species) while hauling in gear. Researchers
urge fishermen to retain all offal so as to not further encourage whales to seek out active
fishing boats (Straley Per. Com 2012, O'Connell Per. Com 2012).
The view on this is from fishermen is mixed; some fishermen agree with not
encouraging the whales to associate boats with food, while others point out that whales
already know to approach fishing boats and if they provide a source of food (offal) the
whales will leave their commercial catch alone (Straley Per. Com 2012, O'Connell Per.
30
Com 2012). Scientists generally feel the least amount of contact and intervention with
marine mammals is best. As with other methods, each fisherman will need to determine
what is in his or her best short- and long-term interest in each distinct situation.
Streamer Devices - In other parts of the world, streamer devices placed next to each
hook have been employed with very encouraging results (McPherson et. al. 2010).
Originally developed for the Patagonian toothfish (Dissostichus eleginoides) fishery off
the Chilean coast, scientists and fishermen have documented a sharp decline in
depredation with the inclusion of these devices (McPherson et. al. 2010, Hamer et. al.
2011, Donoghue et. al. 2003). The underlying idea is that when a fish grabs the bait and
is hooked, the movement will dislodge streamers that will dangle around the fish
(especially during a haul-in of the line). It is believed that the movements of these
streamers, which are made of metallic tape, confuse the whale so it is unable to tell (see)
what its echolocation is fixed on and therefore does not take the caught fish (McPherson
et. al. 2010, Hamer et. al. 2011, Donoghue et. al. 2003).
Picture 6 – Streamer Lines
On the left is a picture of two types of streamer line containers which are placed above
each hook. On the right is a picture of a deployed streamer line. These devices are
currently being used successfully in the Coral Sea longline fisheries. Courtesy of
McPherson et. al. 2010. http://www.iotc.org/files/proceedings/2010/wpeb/IOTC-2010WPEB-Inf17.pdf
31
However, the cost associated with purchasing one streamer for every hook, the
time involved in preparing the gear for deployment, and the time needed after each haul
to reset the gear makes this strategy less desirable. This technique has not caught on in
the Northeastern Pacific longline fisheries, and for the reasons stated previously, is not
recommended. If conditions off the Washington coast change and sperm whale
depredation becomes more prevalent and harmful to the fishing industry, this deterrent
may become a more worthwhile strategy and investment to protect the catch. At present
however, there is simply not enough depredation taking place along the Washington coast
to warrant the inclusion of streamer lines into the longline sets.
Leave the Area While Gear is Soaking - Scientists and fishermen both agree: head
directly to your fishing area, quickly set your gear, and move your vessel five to six miles
away, preferably towards shallow water (200 fathoms or less) to let your gear soak
(Straley Per. Com 2012, O'Connell Per. Com 2012, Dykstra Per. Com 2012). It has been
observed and documented by Alaskan fishermen that whales will wait with a fishing
vessel next to its set until gear retrieval to depredate the line (Straley Per. Com 2012,
O'Connell Per. Com 2012, Dykstra Per. Com 2012). By moving away from the gear, one
can draw the whales off the actual retrieval spot. Shallow water tends to confuse the
whale’s echolocation and a fisherman can sneak away (Straley Per. Com 2012, O'Connell
Per. Com 2012, Dykstra Per. Com 2012).
For retrieval: head directly back to the gear and haul in the line as quickly as
possible. If no whales are immediately present, it typically takes them about an hour or
two to show back up. By working fast, a fisherman can have a large portion of the
longline onboard before the whales return. This strategy is strongly recommended for the
32
Washington coast; especially if whales are present during the set or if there have been
reports of recent sperm whale activity in the area by other fishermen.
Deterrents Currently under Development:
The demand from the commercial longline fishing industry to develop an
effective, cost-efficient device or method to deter depredation is great. As sperm whale
populations continue to increase due to the end of commercial whaling, so too will the
rate of depredation unless something changes to discourage this behavior. SEASWAP,
with the assistance of Alaskan longline fishermen, are presently working at developing
and field testing several new types of depredation deterrent gear that show promising
results (O'Connell Per. Com 2012, Straley Per. Com 2012, Wild Per. Com 2013).
Washington coast fishermen and fisheries managers are encouraged to pay special
interest to these test results.
Acrylic Beads - Researchers for SEASWAP noticed that whales left fish alone if they
were near a tangle in the longline (Straley Per. Com 2012). They speculated that the
whale’s echolocation did not know what it was looking at, similar to the streamer devices
described previously (Dykstra Per. Com 2012). They proposed attaching a 28mm acrylic
bead onto each gangion (the length of line coming off the longline), just above the hook.
The idea is that to the sperm whale’s echolocation, the entire longline will “light up” due
to the beads, confusing the whale and limiting depredation (like radar reflectors on
sailboats) (Straley Per. Com 2012, O'Connell Per. Com 2012, Dykstra Per. Com 2012).
This idea has real potential to be a very inexpensive addition to a longline without
adding extra time to prepare the gear after each haul. Experimental gear testing was
33
conducted during the 2012 longline season in Southeast Alaskan waters (O'Connell Per.
Com 2012, Straley Per. Com 2012). Unfortunately it appears these beads had no
statistically significant effect in deterring sperm whale depredation (Wild Per. Com
2013). It is speculated the acrylic beads were not able to alter the acoustic signal enough
to confuse the whale’s echolocation (Wild Per. Com 2013). Researchers are in the
process of preparing the final report for publication. If this deterrent had been found to be
effective, acrylic beads could have easily and affordably been used by Washington coast
fishermen. Acrylic beads are relatively inexpensive and after the initial output of labor to
attach the beads to each gangion, no additional time or labor would have been required.
It is unfortunate the results of this test weren’t more favorable.
Picture 7 – Acrylic Beads on a Longline
The photograph on the left shows rolls of longline with blue acrylic beads attached. The
photograph on the right shows Jan Straley holding up a gangion with an acrylic bead
above the hook. Courtesy of Alaska Sustainable Fisheries Trust.
http://thealaskatrust.org/whale-research.php
Bubbler - Also in research and development at SEASWAP is a device known as a
“bubbler”; essentially a container full of compressed air much like those used in SCUBA
(self-contained underwater breathing apparatus) diving (O'Connell Per. Com 2012,
34
Straley Per. Com 2012). The container is lowered overboard underneath a longline during
a haul. At depth, the container releases a steady stream of bubbles in an attempt to
disrupt the whale’s echolocation (much like a fighter jet releasing chaff to confuse
missile guidance systems) (O'Connell Per. Com 2012, Straley Per. Com 2012). It is
hoped that this device will be able to generate a “wall of bubbles”; enclosing the longline
and “concealing” the caught fish from the sperm whale’s echolocation (O'Connell Per.
Com 2012, Straley Per. Com 2012). As with the acrylic beads, this would be a relatively
inexpensive deterrent to purchase and operate. After the initial purchase of the canister,
the only other expense would be refilling the canister with compressed air after each
fishing trip. Further use of this strategy will determine whether it is an effective deterrent
and investment.
After the initial field testing during the 2012 Alaskan longline season, problems
with the design were discovered (Wild Per. Com 2013). The canister was not allowing
enough bubbles to escape at the same time. Instead of a “wall of bubbles”, there was
merely a trickle. After the first series of unsuccessful field tests, the bubbler has been sent
back to the engineering department for modifications (Wild Per. Com 2013). Hopefully
the difficulties can be worked out and future tests prove successful. Fishermen and
fisheries managers are encouraged to listen for the latest updates on the bubbler’s status
and potential effectiveness.
35
Picture 8 – A Bubbler Device Currently in Development
A photograph of a prototype bubbler ready for field testing. This device is to be lowered
off the stern of a fishing vessel during the hauling in of fishing gear with the hope of
masking the fish in a wall of bubbles shielding them from sperm whale’s echolocation.
Courtesy of SEASWAP 2012. http://www.seaswap.info/index.html
Decoy Playback Experiments - Currently during the 2013 Alaskan longline season,
experiments are underway testing the effectiveness of decoy playback devices (Wild Per.
Com 2013). SEASWAP, having identified prop cavitation as the “dinner bell” that
attracts the sperm whales to the fishing vessels, is attempting to use this “signal” to draw
off the whales. The study design is relatively simple. A participating commercial fishing
vessel will anchor a buoy at either three or six nautical miles (randomly selected) from
their actual fishing set (Wild Per. Com 2013). Attached to the buoy will be a playback
device with recordings of prop cavitation sounds. One hour before hauling in their gear,
the fisherman activates the playback device remotely (Wild Per. Com 2013). The hope is
any sperm whales in the area will be drawn to the decoy buoy while the fishing vessel
prepares to retrieve their set. By the time the whales realize no fish are coming up by the
36
decoy buoy and find the actual fishing boat, hopefully the majority if not all of the gear
will have been retrieved and the catch safe on board.
SEASWAP plans on outfitting 25 fishing vessels with the decoy playback buoys
and carefully recording the results of each deployment throughout the season (Wild Per.
Com 2013). Washington coast fishermen are encouraged to listen for results of these
experiments.
Depending on the effectiveness of this strategy/device, the initial
investment cost of the necessary equipment, and the rate of increase in sperm whale
interactions, this might be a viable option to deter sperm whale depredation along the
Washington coast.
Conclusion:
The problem of sperm whale depredation is not going to go away on its own,
especially because the reward of easily obtained food is too great for the whales to pass
up (Straley Per. Com 2012, O'Connell Per. Com 2012, Dykstra Per. Com 2012). As the
sperm whale populations continue to increase due to the end of commercial whaling, this
problem is expected to worsen. The economic loss to fishermen, the uncertainty of
standing fish stock to managers, and the danger to the whales themselves are all
important reasons to find an effective deterrent to reduce or ultimately end depredation.
The economic value of fish lost can be quite staggering from season to season, depending
on the price paid per pound and the amount of fish to catch. What was not calculated was
the cost of replacing lost or damaged gear, added fuel and bait costs, and extra time spent
fishing. The bottom line is that a vessel that experiences any level of depredation on a
fishing trip will experience some level of economic loss. Fishermen need to take steps to
37
reduce or prevent depredation in order to keep their operation profitable. Researchers and
fishermen are committed to working with each other to develop and test new
technologies that are effective, affordable, and safe to marine mammals (Straley et. al.
2011).
By employing the strategies recommended in this thesis, Washington coast
longline fishermen can work towards reducing sperm whale depredation to their lines in a
cost-effective manner. More importantly, methods that are currently being developed and
tested are showing promising results. Acrylic beads did not meet scientists’ expectations,
but with adjustments in engineering design, bubblers have the potential to “confuse”
sperm whales’ echolocation and decrease depredation. Current testing of decoy buoys to
document their effectiveness illustrates the collaboration between fishermen and
scientists and their dedication to finding a workable solution. This collaboration between
scientists and fishermen has been mentioned throughout this thesis and should be noted.
Collaboration between scientists and fishermen is key to collecting data, testing new
deterrents, and determining the feasibility of new deterrents in commercial longline
operations.
By learning from the example set in Alaska, researchers and fishermen in
Washington are highly encouraged to work together at finding a solution. What works up
in Alaska might not necessarily work off the Washington coast. The ocean conditions, the
benthic habitat, the weather patterns, the fishing seasons, and type of gear are all
different. Washington coast fishermen need to try the recommendations put forth in this
thesis and find what works. Talk to your fellow fishermen and fisheries managers about
successes and failures. Spread word about strategies and methods that work. The entire
38
fleet needs to become involved in doing everything feasible to deter depredation. If some
vessels do nothing and let depredation occur unhindered, the sperm whales will be
encouraged to continue to seek out active fishing vessels. Fisheries managers need to
actively educate their fleets. The managers have the resources available to gather research
and findings and provide the information to the fishermen. State and tribal managers
should collectively work together in a mutually beneficial partnership to discover the size
and scope of the problem and compare notes on what types of methods and strategies are
working.
In addition, as this is a worldwide problem, scientists all over the world (not just
SEASWAP) are developing and testing new deterrent methods and strategies.
Researchers gather at annual symposiums and conferences to compare notes and findings.
With this focus, it is believed that it will only be a matter of time before an effective, lowcost, minimal-effort deterrent is identified, or a combination of strategies is proven
successful.
Future Research Needs and Discussion:
The goal of this thesis is to provide a document that fisheries managers and
fishermen along the Washington outer coast can utilize to educate themselves about
sperm whales, depredation, important research findings, effective deterrent strategies, and
ongoing research. More importantly, fishermen are needed to become part of the solution.
Identifying the Scope – Quinault longline fishermen have reported sperm whale
depredation events to their fisheries managers beginning around 2008 and continuing
through the present season. Inquiries were made to other Washington tribal fisheries
39
managers and to the Washington Department of Fish And Wildlife (WDFW) fisheries
managers to see if they were also getting reports from their fishermen. None indicated
any reports of sperm whale depredation from their fishermen. It is unlikely that Quinault
fishermen are the only vessels encountering depredation. What is more reasonable is that
no other fishermen are reporting these instances to their managers. A survey of all
Washington coast fishermen is recommended to discover exactly how big the problem is
and in what areas depredation is occurring and at what rate. This information is vital to
understanding the scope of the problem.
Sperm Whale/Longline Interaction Logbook - Located on the following pages is a
copy of a sperm whale/longline interaction logbook distributed by SEASWAP and
currently used by Alaskan commercial longline fishermen (Straley Per. Com 2012,
O'Connell Per. Com 2012, Dykstra Per. Com 2012). It is highly recommended that
Washington coast longline fishermen make or obtain copies of this form, keep them on
their vessels, complete them for every whale interaction, and submit the forms to their
fisheries managers (Straley Per. Com 2012, O'Connell Per. Com 2012, Wild Per. Com
2013).
The intent of the sperm whale/longline interaction logbook is to document sperm
whale depredation events to better understand the frequency and extent of the problem
along the Washington coast. Obtaining this information from Washington longline
fishermen is vital to better understand the scope of the problem (Straley Per. Com 2012,
O'Connell Per. Com 2012, Wild Per. Com 2013). This problem could have gone
unnoticed for years if it were not for Quinault Indian Nation longline fishermen bringing
it to the attention of their fisheries managers (Charley Per. Com 2008, Frank Per. Com
40
2013, Rhoads Per. Com 2013). It is the fishermen themselves who need to take an active
part in documenting depredation, collecting data, and collaborating with researchers and
fellow fishermen.
41
Table 4 - Sperm Whale/Longline Interaction Logbook
42
Educating Fishermen - Also included on the following pages is a table listing the most
common deterrent strategies available and rating their effectiveness for the Washington
coast fishermen. This table was created for fisheries managers to copy and distribute to
their fishermen for the purpose of easily educating them about their current options for
dealing with sperm whale depredation. Just as fishermen need to take an active role in
documenting interactions and collecting data, fisheries managers and researchers also
need to work closely with the fishermen to share options, current and future research, and
possible solutions (Straley Per. Com 2012, O'Connell Per. Com 2012, Wild Per. Com
2013). Alaska is a perfect example of what can be accomplished when fishermen and
scientists work together toward a common goal. The fishermen brought this problem of
sperm whale depredation to the attention of the scientists. The scientists relied on the
fishermen to collect interaction data (sperm whale/longline interaction logbooks).
Through experimentation and field studies, scientists were able to identify what attracted
whales to actively fishing vessels (prop cavitation). Deterrent methods were proposed by
scientists; fishermen tested the new strategies and reported their effectiveness to the
scientists. Fishermen also developed different strategies on their own and passed the
word to their fellow fishermen (i.e., group hauls). This partnership with fishermen and
scientists continues today.
43
Table 5 – Educational Handout on Depredation Strategies for Fishermen
Deterrent
Method
Brief
Explanation
Pros
Cons
Effectiveness
Recommendation
for WA Fishermen
Acoustical
Deterrents
Devices such
as seal bombs,
pingers,
recordings of
killer whales,
etc. utilized to
chase off
whales.
Very
effective on
the short
term. Some
devices such
as seal
bombs are
relatively
inexpensive.
Whales will
become
acclimated to
the sounds and
the deterrents
will cease to
work on the
long term.
Some devices
are very
expensive to
purchase and
maintain.
Very effective
on the short
term.
While these devices
show great promise
at deterring whales
on the short term,
there is a potential
to cause harm to the
whales. Therefore,
in order to avoid
hefty fines under
the Marine
Mammal Protection
Act, these devices
are not
recommended.
Dummy Sets
The
deployment of
dummy
fishing gear
miles from the
actual fishing
gear in order
to draw the
whales off.
A relatively
small
investment
of time and
money to the
fishermen
The whales
will still be
attracted to the
sounds of an
actual gear
haul and will
lose interest in
the dummy set
in search of
real food.
Somewhat
effective.
If the fishermen
have whales
following their
vessel, it is
recommended that
this method be tried
in attempt to fool
the whales away
from the actual
fishing gear.
Group Hauls
Fishermen
coordinate
among
themselves
and either all
haul at the
same time, or
one fisherman
hauls in gear
while another
several miles
off cycles in
and out of
gear in
attempt to lure
the whales
away.
A relatively
small
investment
of time and
money to the
fishermen.
During a group
haul,
depredation is
still occurring.
This method
has the
potential to be
quite effective
when only a
small number
of whales are
present.
Washington coast
fishermen should
try this deterrent
method. It shows
great promise for
groups of whales
fewer than 3 or 4.
When more whales
are present, another
method should be
tried.
44
Deterrent
Method
Brief
Explanation
Pros
Cons
Effectiveness
Recommendation
for WA Fishermen
Circle Hauls
Maneuvering
one's vessel in
reverse while
circling one's
gear while
hauling in
gear.
By using this
technique,
the
fisherman
will not have
to
continually
be shifting in
and out of
gear and
therefore
will
eliminate
prop
capitations
sound which
attracts
whales.
This method
can only be
used on certain
vessels when
ocean
conditions are
relatively
calm.
This method is
highly
effective at
eliminating the
sounds that
alert whales to
actively fishing
vessels.
If the ocean
conditions are right
and the vessel is
capable, this
method is strongly
encouraged.
Hydrophone
A listening
device used to
determine if
whales are
present before
hauling in
gear.
Fairly
inexpensive
(around
$200 to
$400).
The whales
might be in the
area for days;
the fishermen
can only wait
so long.
Hydrophones
are very
effective at
determining
the presence or
absence of
whales
While a hydrophone
does not deter
whales, fishermen
can determine if
whales are actually
present prior to
hauling in gear. If
whales are present,
the fishermen can
then incorporate
another deterrent
method to protect
their catch. The
purchase and use of
a hydrophone is
recommended.
45
Deterrent
Method
Brief
Explanation
Pros
Cons
Effectiveness
Recommendation
for WA Fishermen
Shorter
Longlines
Fishing with
shorter
longlines so
the gear can
be recovered
before whales
arrive at the
site.
If whales are
several miles
off, this
method can
be quite
effective and
gear
recovered
before the
whales
arrive.
Shorter
longlines
means smaller
catch. More
sets would
need to be
made to equal
out the loss.
This means
spending more
time on the
fishing ground,
and therefore
increasing the
likelihood of a
whale coming
to investigate.
This method
can be quite
effective if no
whales are in
the immediate
vicinity.
This method has the
potential to be a
quite effective
strategy for
fishermen with
smaller vessels. The
operating expense is
lower; therefore,
less fish would be
needed to be caught
in order to make a
profitable trip.
Night
Hauling
Hauling gear
at night to
avoid
detection by
whales.
There are no
pros.
This method is
completely
ineffective.
This method
simply does
not work.
This method is not
recommended
simply because it
does not work.
Echosounder
Turing off
one's
Echosounder
prior to
hauling in
gear so the
sound does
not attract
whales.
There are no
pros.
This method is
completely
ineffective.
This method
simply does
not work.
This method is not
recommended
simply because it
does not work.
Avoiding
Whale
Hotspots
Concentrating
one's fishing
areas where
whales are
known not to
frequent.
By fishing in
areas not
populated by
whales, the
chances of
attracting
one increase
dramatically.
Unfortunately,
whales tend to
inhabit the best
fishing
grounds.
Unfortunately,
the whales are
naturally
attracted to
where the fish
are. Areas
without whales
are typically
poor fishing
spots.
If the fishermen
know of an area
where whales are
absent, but fishing
is good, by all
means employ this
strategy.
46
Deterrent
Method
Brief
Explanation
Pros
Cons
Effectiveness
Recommendation
for WA Fishermen
Firearms
The use of
firearms to
deter whale
depredation.
There are no
pros.
This method
simply does
not work.
Due to the
thickness of the
whale's blubber
layer,
projectiles
from firearms
will have little
to no effect on
the whales. At
the most, the
whales would
simple stay
submerged
longer but
continue
depredating.
In order to avoid
hefty fines under
the Marine
Mammal Protection
Act, and because
this deterrent
method is
completely
ineffective, this
strategy is strongly
discouraged.
Eliminate
Offal
Discharge
Retaining all
by-catch and
refuge from
gutted fish
until fishing
activity is
over.
By
withholding
extra
potential
food, whales
will be less
attracted to
the vessel.
By not
providing the
whales extra
food, they
have only the
caught fish to
eat and
therefore, the
amount of
depredation
would be
greater.
At this time
there are mixed
views on
whether this is
an effective
method or not.
Washington coast
fishermen are
encouraged to try
both withholding
and discharge of
offal and to report
their finding back to
fellow fishermen
and researchers.
This method is still
up in the air.
Streamer
Devices
A device
attached
above each
hook that
deploys a
streamer when
a fish is
caught. The
streamer helps
mask the fish
to the whale's
echolocation.
This method
is quite
effective in
the Coral
Sea longline
fishery.
The cost of
added gear and
time needed to
attach the gear
and to reset the
gear after
deployment is
extensive.
This method is
very effective
and proven in
other longline
fisheries in the
world.
Due to the added
expense of time and
money, this method
is not
recommended. The
Washington coast
simply does not
have that big of a
depredation
problem to warrant
this device.
However, this might
change in years to
come.
47
Sperm Whale Identification and Documentation - A vital piece of information
presently missing is whether Washington coast has its own resident population of sperm
whales or if whales migrating up to Alaska depredate the Washington longline fleet along
the way, as is presently assumed (Straley Per. Com 2012, O'Connell Per. Com 2012,
Calambokidis Per. Com 2012, Wild Per. Com 2013). Photo identification of suspect
whales is required; an individual whale can be identified through pictures of its flukes
(each whale’s fluke has a distinctive shape and markings much like a person’s
fingerprint) (Straley Per. Com 2012, O'Connell Per. Com 2012, Calambokidis Per. Com
2012). Fluke pictures taken of sperm whales engaged in depredation along the
Washington outer coast can be compared with whale photo catalogs from SEASWAP and
Cascadia Research Collective (Straley Per. Com 2012, O'Connell Per. Com 2012,
Calambokidis Per. Com 2012).
If the Washington coast photos match those from whale fluke pictures taken at a
later date up in Alaska, it can be surmised that those whales migrated north and
depredated the Washington fleet along the way. If Washington coast photos match
pictures previously taken in Washington, it could potentially indicate that the whales are
staying in the area (Straley Per. Com 2012, O'Connell Per. Com 2012, Calambokidis Per.
Com 2012). One other possibility would be that whales depredating in Alaska for several
years prey on the Washington fleet as they return south to breed with females.
Fishermen are encouraged to carry a camera on board their vessels and to
photograph sperm whale flukes if possible. The date, time, and GPS coordinates of each
encounter should be recorded and provided to fisheries managers with the photographs
for distribution to researchers. Scientists are also encouraged to schedule research cruises
48
during longline fisheries for the purpose of obtaining fluke shots of sperm whales in the
vicinity of fishing operations (Calambokidis Per. Com 2012). Fishermen are usually too
busy in their work to stop what they are doing to photograph suspect whales. They are
more interested in getting their gear on board as quickly as possible (Frank Per. Com
2013, Rhoads Per. Com 2013). A solution to this would be to have any fishery observers
on board trained and equipped to photograph whales for identification purposes.
49
Picture 9 – Pictures of Individual Sperm Whale Flukes
Photos of sperm whale flukes showing distinct markings for each, which researchers can
then use to identify individual whales. Through multiple sightings, the whale’s movement
can be tracked and documented. Courtesy of SEASWAP.
http://www.seaswap.info/study/photoid.html
Fishermen on the Front Line - A special note for fisherman: you are an important part
of this research and need to take an active role in finding a solution. You are urged to use
the recommendations and advice contained within this thesis. Try different sperm whale
deterrent strategies and share with others what works and what does not. Invent and test
50
new strategies. We can learn much from following Alaska’s example, but what works up
in Alaska might not necessarily work on the Washington coast. Play an active role in
assisting researchers with data collection and report all sperm whale interactions. With
everyone coordinating and working together, a viable solution that benefits all
stakeholders will certainly be found. The ultimate goal would be to keep sperm whale
depredation to a minimum using methods that are affordable, easy for fishermen to
incorporate into their longline operations, and prevent harm to the whales.
51
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