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Title
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Blue Whale (Baleanoptera musculus) Ship Strike Threat Assessment in the Santa Barbara Channel, California
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Date
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2009
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Creator
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Laggner, Daniel
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Subject
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Environmental Studies
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extracted text
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BLUE WHALE (Baleanoptera musculus) SHIP
STRIKE THREAT ASSESSMENT IN THE SANTA
BARBARA CHANNEL, CALIFORNIA
by
Daniel Laggner
Thesis: Essay of Distinction
Submitted in partial fulfillment
of the requirements for the degree
Master of Environmental Study
The Evergreen State College
June 2009
i
© {2009} by {Daniel Laggner}. All rights reserved.
ii
This Thesis for the Master of Environmental Study Degree
by
Daniel Laggner
has been approved for
The Evergreen State College
By
________________________
{Alison Styring}
Member of the Faculty
_______________________
Date
iii
Abstract
Blue Whale (Baleanoptera musculus) Ship strike Threat Assessment in
the Santa Barbara Channel, California
The blue whale is the largest baleen whale and also the most massive animal to inhabit
global waters (1979; Perrin, Wuersig, & Thewissen, 2002; Jefferson, Webber, & Pitman,
2008). From the early 20th century until 1966 some 330,000 blue whales were harvested
in northern and southern waters, but most were taken from the Antarctic region (Reeves
R.R., 1998; Bortolotti, 2008; Gambell, World Whale Stocks, 1976; Gambell, The Blue
Whale, 1979; Ellis, 1991). This population decline caused the International Whaling
Commission (IWC) to ban the hunt of blue whales in 1966 (Ellis, 1991). Modern research
tools have provided insights into the abundance and distribution of blue whales
(Calambokidis J., 2003; Calambokidis, Douglas, Falcone, & Schlender, 2007). The
northeast Pacific blue whale population is one of the largest populations globally with an
estimated 1,400 animals (Calambokidis, Douglas, Falcone, & Schlender, 2007). This
population has shown little growth since the end of whaling when compared to other
whale species such as the sperm or humpback (Bortolotti, 2008). Studies indicate ship
strikes may be a threat to the recovery of northeast Pacific blue whale populations
(Jensen & Silber, 2004). The Santa Barbara Channel in central California is a region
hosting both shipping lanes and the feeding habitat of blue whales. In September of 2007,
six blue whales were fatally struck, all of which occurred in the Santa Barbara channel
region (Cascadia Research unpublished data). Upon assessment, ship strikes have been
determined to be a threat on the population scale, potentially causing slowed growth or
even decline. Several conservation strategies could be employed including vessel speed
reduction, shipping lane shift, and posting observers on commercial vessels. Further
studies are critical to advance the knowledge and technology that could mend this issue.
Table of Contents
Introduction.………………………………………………………………………….……………. .1
Chapter 1: BLUE WHALE BIOLOGY AND THE HISTORY OF POPULATION
DECLINE…………………………………..……………...………………..………….. 2
Taxonomy……………………………………………………..…...……………….……….…….. 2
Reproductive Biology……………………………………...……..…………….…………….….. 4
History of Blue Whale Decline……………………………………..……………………….…. 6
Technological Advancement of Rorqual Whaling (1873 – 1923)………………………..… 6
Floating Factories………………………………………………………………………………… 7
Whaling Antarctica (1906-1962)…………………………………………………………...…… 7
The Global Shift of Whaling (1950-1966)………………………………………………..…… 10
The Implementation of Whaling Regulations (1961-1972)…………………………………. 12
Chapter 2: BLUE WHALE STUDY METHODOLOGIES…………….………...… 13
Photographic Identification/Line Transect Surveys……………….……………..…..….….. 14
Bioacoustic Tags……………………………………………………….…………....…..…...….. 16
Tag Observations of Feeding and Dive Behavior……………………………………………. 17
Lunge dives………………………………………………………………………………………... 18
Diurnal Dive Pattern…………………………………………………………………………….. 19
Chapter 3: CURRENT ABUNDANCE ESTIMATES OF NORTH EAST PACIFIC
BLUE WHALES………………………………………...…………………………….. 22
A Brief on Global Estimates……………………….……………………………………………. 22
North East Pacific Population………………………………………………………………….. 23
Abundance……………………………………………………………………………………….... 25
Distribution…………………………………………………………………………………......… 26
Discussion……………………………………………………………………………………...…..27
Chapter 4: SHIP-WHALE INTERACTION ASSESSMENT: The Santa Barbara
Channel…………………………………….………………………………….…….…. 28
Ship Detail……………………………………………………………..……………….…...……. 30
Vessel Types…………………………………………………………………...……….……....…. 30
Vessel Speeds…………………………………………………………………..……….………… 31
Ship-Whale Interaction…………………………………………….………………….……….. 32
Ship Strikes in the Santa Barbara Channel…………………….……………..……….……… 32
Causes of Injury or Death……………………………………………………..……….……….. 34
Population Threat………………………………………………………………………...……… 35
Chapter 5: FUTURE BLUE WHALE STUDIES AND POSSIBLE
CONSERVATION STRATEGIES…………………………………...………..…….. 37
Unknowns………………………………………………………………………………..….….…. 38
Continued Research…………………………………………………………………..…..….….. 39
Possible Strategies to Avoid Ship Strikes…………………………………………..….……… 41
References…………………………………………………………………………………………. 42
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List of Figures and Tables
Figure 1: Blue whale taxonomic shape.…...………………………………….………….. 3
Figure 2: Estimated population shift from pre-whaling to the present………...……….. 11
Figure 3: Line transect survey and sightings 1991-1996.………………….….………… 15
Figure 4: Blue whale photographic identification...……………….…………..………... 15
Figure 5: Bioacoustic probe and attachment method…..………….…………..………... 17
Figure 6: Blue whale lunge dives into krill layers……...………….…………..…………19
Figure 7: Diurnal dive pattern chart……….…………………….……………………... 20
Figure 8: Distribution of northeast Pacific blue whales...……….……………………… 26
Figure 9: Ship tracks in the Santa Barbara Channel………………….………………… 29
Figure 10: Frequency of ship strikes in relation to ship speed chart………….………... 31
Figure 11: Sightings and movements in the Santa Barbara Channel…...………………. 33
Figure 12: Locations of deceased blue whales, fall 2007..……..…………….…………. 34
Figure 13: Bulbous bow of commercial ship vessel..…………...…………..…………… 35
Table 1: Northeast Pacific blue whale abundance..……………..……………………… 25
Table 2: Total past blue whale ship strikes….……………….…………….………….... 32
Table 3: Summary of deceased blue whales, fall 2007.....…………………..………...… 33
v
Page 2
Acknowledgements
I would like to thank Cascadia Research Collective for their information and support.
Thank you to Alison Styring, my reader, who helped me get through this process with her
detailed edits and helpful comments. It was a pleasure to have her as a reader. Since
English is not my first language, I want to thank my mother, who helped me identify my
German-English mistakes, as well as skillful edits. Some of the formatting this piece
required were beyond my skill, but my father had the skill and heart to help me willingly.
Thanks to my brother, who was always there to listen to me complain. Thanks to all my
friends for supporting me.
vi
Page 3
Introduction
Ship strikes occur regularly where feeding habitat of whales and shipping lanes overlap
(Bortolotti, 2008; Douglas 2008). A detailed assessment is needed to determine that this
has the potential to slow or halt population growth of blue whales in close association
with large vessel traffic. The research presented in this document will shed light on the
threat of ship strikes slowing population growth on the northeast Pacific blue whale
population, situated in the Santa Barbara Channel, which also hosts shipping lanes. The
objective is to bring to light a conservation issue that has not been perceived as a danger
to a fragile wildlife population.
Oceanic upwelling events transport cold, nutrient rich water close to the surface bringing
with them plankton and krill; the staple diet of blue whales (Chandler, 1999). Such
upwelling is newly (20-30 years) occurring within the Santa Barbara Channel, which is
attracting a dense population (see chapter 3) of blue whales (Larkman & R.R., 1998;
Calambokidis, Douglas, Falcone, & Schlender, 2007). Chapter one shows that this
population is fragile due to an abnormally slow recovery from six decades of whaling
(Bortolotti, 2008). In chapter two, study methodologies are presented that show how
researchers understand blue whale population dynamics and diving/feeding behavior
(Calambokidis J., 2003; Calambokidis, et al., 2007/08). Another important consideration
for a ship strike assessment, shown in chapter 3, are the current abundance and
distribution estimates of northeast Pacific blue whales. In chapter four, a threat
assessment of ship strikes on northeast Pacific blue whales is made, given current
literature and research. Finally, chapter five provides insights into the future of blue
whale conservation, and presents strategies to prevent further ship strike events.
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Chapter 1
BLUE WHALE BIOLOGY AND THE HISTORY OF POPULATION DECLINE
Taxonomy
The blue whale, (Linnaeus 1758), is a species of baleen whale (Perrin, 1979; Wuersig, &
Thewissen, 2002; Jefferson, Webber, & Pitman, 2008). It belongs to the largest group of
baleen whales, commonly known as rorquals (Jefferson, Webber, & Pitman, 2008). By
mass, the blue whale is the largest animal known to have ever lived on Earth (Gambell,
1979; Reeves R.R., 1998). Adults in the Antarctic have reached a maximum body length
of about 30 m and can weigh more than 150,000 kg (Reeves R.R., 1998). Blue whales in
the Northern Hemisphere are generally smaller than those in the Southern Ocean. As is
true of other baleen whale species, female blue whales are slightly larger than males
(Ralls, 1976).
Blue whales are long-bodied and slender (figure 1) with a dorsal fin that is
proportionately smaller and set further back than those of other baleen whales (Jefferson,
Webber, & Pitman, 2008). Their rostrum is broad and flat. When a blue whale is feeding,
its pleated throat and chest area expands to engulf an enormous amount of seawater and
food. The water is then expelled and the filtered zooplankton is swallowed, after which
the body outline returns to its characteristically slender shape (Reeves R.R., 1998).
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Figure 1.The slender shape of the blue whale allows it to travel efficiently over long
distances (image provided by Cascadia Research Collective)
The animals’ color pattern is a mottled gray, which appears light blue when seen through
the water. The characteristic pattern is unique to each animal and acts like a fingerprint in
matching individuals for long-term photographic identification studies.
Studies of intra-specific variability have led to the designation of three subspecies
(Jefferson, Webber, & Pitman, 2008): (a) B. m. in the Northern Hemisphere, (b) the
slightly larger B. m. intermedia from the Antarctic and (c) the so-called "pygmy" blue
whale, B. m. brevicauda, a smaller and morphologically distinct species found in the subAntarctic zone of the southern Indian Ocean and southwestern Pacific Ocean (Perrin,
Wuersig, & Thewissen, 2002; Jefferson, Webber, & Pitman, 2008). There is also a
"resident" population of blue whales (of unknown taxonomic status) in the northern
Indian Ocean from the Gulf of Aden, going east at least to the Bay of Bengal (Reeves
R.R., 1998). This population was named Balaenoptera indica by Anderson (1879).
B. m. musculus, making up the northeast Pacific population, reside in an area (from
British Columbia to Costa Rica) where ship strike threats are the highest. The densest
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part of this population (see chapter 3) (Calambokidis, Douglas, Falcone, & Schlender,
2007) occurs seasonally in central California, where ship traffic and feeding habitat
overlap. This makes the northeast Pacific population particularly vulnerable to ship
strikes.
Reproductive Biology
Little literature exists on this facet of blue whale research. Blue whale reproduction is
still part of the mysterious behavior of these elusive animals. Neither copulation nor
birthing of blue whales has ever been recorded. Though little is known about the specifics
of reproductive and courting behaviors, enough is known for a basic understanding of
population dynamics.
Gestation period for blue whales is approximately 10-12 months, and calves are nursed
for about 6-7 months (National Marine Fisheries Service, 1998). Reproductive activity,
including mating and births, takes place in the winter season (National Marine Fisheries
Service, 1998). Weaning most likely occurs either at or during the migration to the
summer feeding areas. Average calving interval is probably two to three years. The age at
attainment of sexual maturity is uncertain but is thought to be 5-15 years (Yochem and
Leatherwood 1985). Due to the problems of determining the lifespan of blue whales, the
estimated lifetime reproductive output of an average female is still uncertain. Experts
estimate animals to have an average life span of 30-80 years (Jefferson, Webber, &
Pitman, 2008). Since sexual maturity is not reached until approximately 5-15 years of age
(Perrin, Wuersig, & Thewissen, 2002) and calving interval is approximately every 2-3
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years (Perrin, Wuersig, & Thewissen, 2002) one can qualitatively estimate that an
average mother has the potential to produce approximately anywhere from 2-20 offspring
in her lifetime (Cascadia Research Collective unpubl. data). Unfortunately, at this time no
recorded and published lifelong reproductive output exists.
The distribution of these animals is global, yet their worldwide abundance today could be
as low as 10,000-15,000 animals (Gambell, 1976; Bortolotti, 2008). It has been estimated
that well over 300,000 blue whales (estimations of up to 350,000 animals (Gambell,
1976)) inhabited the oceans before the early 1920’s (Jackson, 1978). During some six
decades of whaling more than 330,000 blue whales were harvested and their population
was drawn to near extinction (Bortolotti, 2008). This dramatic decline has made the blue
whale vulnerable to extinction. Furthermore, because of their slow reproductive output
and low population numbers ship strikes may be threatening blue whale population
growth.
History of Blue Whale Decline
Blue whales were not hunted before the early 1900’s because the technology could not
compete with the animal’s large bodies and fast speed (Calambokidis & Steiger, 1997:
Bortolotti, 2008). This changed when Norwegian whaling Captain Svend Foyn, invented
a new technology that formed the foundation of modern commercial whaling
(Calambokidis & Steiger, 1997). Foyn used funds from his success in sealing operations
and launched a steam-powered boat specifically designed to catch whales (Calambokidis
& Steiger, 1997). Though blue whales were the target, other species such as sei,
Page 8
humpback and fin were also hunted. The technology began to prove successful while
only few laws existed on whaling restrictions. Thus rapid development of modern
whaling set the stage for global expansion of the industry (Calambokidis & Steiger,
1997).
Technological Advancement of Rorqual Whaling (1873 – 1923)
It took a combination of increased vessel speeds and weaponry to kill an animal as large
and fast as the blue whale. The concept of a harpoon cannon had been around since the
1730’s, but no one had built one that whalers could use (Bortolotti, 2008). The early
designs were awkward to use, dangerous, and fired only small harpoon heads that were
inadequate for blue whales (Bortolotti, 2008).
In the 1820’s English rocket scientist William Congreve tested a harpoon propelled with
black powder and fitted it with a shell that exploded on impact with the whale (Ellis,
1991). This proved a successful method of killing a blue whale, but the animal sank once
it died. Over several decades of trial and error, the harpoon changed from exploding on
impact, to exploding a few seconds after it was embedded in the animal (Jackson, 1978).
To solve the problem of the sinking animals, whalers pulled alongside the dead animal
and inserted an inflatable tube into the body cavity, which kept it afloat. The technology
for hunting blue whales and other rorquals was in place by 1873, but Svend Foyn claimed
a patent for it and had a monopoly on hunting blue whales (Ellis, 1991). Once Foyn’s
monopoly expired in 1883, other companies began taking blues and the annual take
increased dramatically (Ellis, 1991). By the turn of the century, Norwegian whalers were
rapidly declining large rorqual populations in the northeastern Atlantic (Bortolotti, 2008).
Page 9
Floating Factories
Whalers began experimenting with a new way of processing whales on “floating
factories” (Jackson, 1978). Up until this point boilers and separators had been used on
shore. A prototype vessel of approximately 1,500 gross tons required a crew of 60 and
was now capable of moving operations into the open sea (Jackson, 1978). In 1923
Norwegian captain Carl Anton Larsen (b. 1870) sailed the first pelagic factory ship (The
Sir James Clark Ross) south into the Ross Sea off of Tasmania (Jackson, 1978). As whale
stocks near land bases began to decline, floating factories could be taken out to sea for
weeks at a time. As they evolved, the vessels eventually were able to displace more than
13,000 tons and carried a 500-man crew (Jackson, 1978). Still several problems existed
with these ships until the introduction of (1) the “stern slipway,” which allowed a whale
to be hauled onto the stern and (2) the “whale claw,” a device that fastened around the tail
fluke and tightened automatically when tugged (Bortolotti, 2008; Jackson, 1978; Ellis,
1991). These represented the final technological advancements in the efficiency of
whaling.
Whaling Antarctica (1906-1962)
With declining populations of large whales in northern waters, sights shifted from the
north Atlantic to the southern waters of a small island off the coast of Antarctica called
South Georgia.
“If the blue whale is eventually to disappear from the earth, it would be
safe to say that the seeds of its extinction were sown on a lonely Antarctic
island called South Georgia.” (Bortolotti, 2008).
Page 10
In the hopes of finding a “ripe stock” of unexploited populations of right whales, Captain
Larsen made the first whaling-specific journey to Antarctica in September of 1895
(Jackson, 1978). Still ill-equipped to hunt large rorquals, he watched humpback, fin and
blue whales swarm his ship without a way to tap into this natural resource. It wasn’t until
the early 20th the century that Larsen returned to the South Georgia region for whaling
(Jackson, 1978). He used the sheltered bays of the island to build a whaling station,
which made an ideal setup to begin hunting the populations of large whales. Humpback
whales were the first species to be hunted in this region (Bortolotti, 2008). Within six
years British and Norwegian fleets working in the untapped waters, took 6,197 humpback
whales (Jackson, 1978). As this species became increasingly rare, blue whales were the
next target for whaling in those waters. The season of 1914-15 saw more the 2,300 blues
hunted, with another 1,800 killed in the nearby South Shetlands (Jackson, 1978). During
these early years of modern whaling, the bounty was so plentiful that not all of the
whale’s blubber was taken. Only the thickest blubber on the animal was cut off and the
rest was discarded. This practice eventually led to regulations stating that whalers must
make use of the entire carcass. With the Antarctic whaling practice in full boom, a steady
population of 150 men resided in South Georgia, which then became the southernmost
inhabited point of land on the planet (Bortolotti, 2008).
The arrival of World War I slowed the whaling industry as both ships and men were
needed for the military (Ellis, 1991). Nonetheless whaling continued, and during each of
the four wartime seasons, almost 3,900 blue whales were killed (Ellis, 1991). After the
war, most of the harvested whale blubber got processed into margarine (Bortolotti, 2008).
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By the 1920’s chemists had removed the fishy aftertaste and refined hydrogenation
techniques after which whale oil was almost exclusively converted into margarine
products (Bortolotti, 2008). The whaling seasons of 1929-30 and 1930-31 produced the
highest catch numbers the world had yet seen, with approximately 48,000 blue whales
harvested (Bortolotti, 2008).
Antarctic whaling continued steadily for two decades until World War II slowed the
industry (Ellis, 1991). The season of 1940-41 produced 5,000 animals, taken mostly by
the Japanese, who had not yet entered the conflict (Ellis, 1991). The catch drastically
dropped to about 200 whales for the combination of the next 2 seasons. From 1943-45,
Norwegian expeditions killed around 1,400 blue whales, but collectively, the five war
years produced about the same amount of blue whale kills as the first decade of the
century (Bortolotti, 2008; Ellis, 1991). Many in the industry hoped that this would allow
blue whale stocks to recover from the decline of some 48,000 harvested animals that had
occurred from 1929-31 (Bortolotti, 2008). That was not to be. Once the war ended,
Norwegian, British, Soviet and Japanese whalers continued to hunt blue whale
populations in southern waters. This was not an adequate amount of time for any
substantial population recovery.
The Global Shift of Whaling (1950-1966)
By the 1950’s only about 1,200 blue whales were killed per season and whaling’s focus
shifted to the fin whale (Bortolotti, 2008). At this point in whaling, during the 1950’s, a
ban of blue whale takes would have hardly affected whaling profits. With looming threats
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such as the declining price in whale oil increasing labor costs, and lower productivity due
to decreasing whale populations, companies did not put a ban on hunting blue whales
(Ellis, 1991; Bortolotti, 2008). Compared to smaller whales, blues yielded high amounts
of blubber, requiring fewer animals and less work to reach quotas (Bortolotti, 2008).
Despite blue whale population declines, companies continued to pursue them into the
1960’s (Bortolotti, 2008).
In other oceans, approximately 30,000 blues were taken out of southern waters, 8,200
from the north Pacific and 7,000 from the north Atlantic (Branch, Matsuoka, &
Miyashita, 2004). When a committee was put in place to assess the remaining Antarctic
population in 1963, they found no more than 600 individuals (Bortolotti, 2008). Once the
ocean’s largest population, Antarctic blues had been reduced to a startling 0.15% of their
original size (Branch, Matsuoka, & Miyashita, 2004).
In figure 2, the effect of whaling on global populations can be seen. The noticeable
difference between the decline (from pre-whaling to the 1930’s) and the slow population
increase (from 1965 on) shows the impact that the whaling industry has had on blue
whale stocks.
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Figure 2. Though global populations are increasing, it will be a long recovery before original numbers are once again
reached (population values are approximate).
The Implementation of Whaling Regulations (1961-1972)
With the decline of Antarctic populations, the last shore station in South Georgia closed
after the 1961-62 season (Bortolotti, 2008). The British and Dutch left the Antarctic and
began selling their vessels and equipment because it was not worth the expense to hunt
the scarce population (Jackson, 1978; Mowat, 1972). During an International Whaling
Commission (IWC) conference in 1964, whaling countries reported lower numbers of
blue whales than in the past (Bortolotti, 2008). Norwegian whalers reported that they had
only seen eight blue whales, four of which they had killed (Bortolotti, 2008; Mowat,
1972). The following year only the Soviets saw blue whales and reported killing 20 of
them, though far more were taken unreported (Bortolotti, 2008).
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In 1965 the nations of the IWC agreed, to ban killing the blue whale (Bortolotti, 2008;
Ellis, 1991; Jackson, 1978; Mowat, 1972).
Despite the IWC’s ban on blue whale catches, thousands of animals continued to be taken
illegally. Between 1947 and 1972 soviet whalers took 43,000 humpbacks, 21,600 sperm
whales and 9,200 blue whales (Mowat, 1972; Bortolotti, 2008). Many of these were taken
after the IWC’s ban, with 500 killed as late as 1971-72 (Bortolotti, 2008). After 1961 the
soviets illegally killed almost 700 blue whales in the North Pacific (Bortolotti, 2008).
These statistics came to light in 1993 and helped explain why blue whale populations had
not recovered after nearly 30 years of protection (Bortolotti, 2008). In 1971-72, with the
instatement of required observers on every whaling vessel, violations stopped almost
immediately (Bortolotti, 2008).
It wasn’t until the mid 1980’s that attention towards blue whales was reawakened. This
time it was not for hunting; it was for research. Populations were slowly beginning to
recover and organizations such Cascadia Research Collective began taking photographs
of blue whale sightings (1986) to begin monitoring their population distribution and
abundance. The time had finally arrived to focus research attention on this fragile species
and begin to understand their behavior for conservation purposes.
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Chapter 2
BLUE WHALE STUDY METHODOLOGIES
By the time the IWC’s ban on hunting blue whales went into effect in 1966 (Gambell,
1979) their numbers had been depleted from about 350,000 world-wide to some
15,000 animals. Blues were therefore officially declared endangered (Barlow, et al.
1995; Gambell, 1976; Calambokidis, Schorr, et al. 2007/08; Gambell, 1979). Despite
the IWC’s protective measures blue whale populations have remained low in
numbers, with little to no recovery (Calambokidis, et al., 2007/08). In the four
decades of blue whale protection, populations have shown approximately only 3%
recovery (Barlow, et al. 1995; Gambell, 1976; Calambokidis, Douglas, Falcone, &
Schlender, 2007). Little is known about why blue whale recovery is slow. Reasons
may include illegal whaling, lack of food sources, and ship strikes (Calambokidis, et
al., 2007/08). It is difficult to study animals that travel great distances in a short
amount of time and spend most of their lives out of the visual range of humans. The
methods to gather the necessary data are important in analyzing the threat of ship
strikes. Researchers must first have an understanding of the animal’s distribution,
dive patterns, feeding behaviors and movement patterns.
Over the past two decades the methodologies of studying blue whales have
developed into: (1) photographic identification used to determine long-term migration
and distribution patterns (J. G. Calambokidis 1990; Calambokidis, et al. 2007;
Calambokidis and Barlow, 2004), (2) ship surveys to examine distribution and
abundance (Calambokidis, Douglas, Falcone, & Schlender, 2007; Dohl, 1983), (3)
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satellite tagging (Mate B. B., 1999) and most recently (4) acoustic studies using
underwater hydrophones, acoustic arrays and suction cup tags to determine whale
distribution and underwater feeding behavior (Calambokidis, et al., 2007/08).
Blue whale research is beginning to reveal insights into previously unknown facets of
their lives. The techniques used and their results portray vital data for a thorough
threat assessment of ship strikes. Vital pieces of data for this analysis include: the
distribution of blue whales in relation to shipping lanes (studied via ship surveys,
mark recapture modeling and photographic identification, Cascadia Research
Collective 2006), as well as their dive patterns and feeding behavior (studied via
bioacoustic tagging, Cascadia Research 1999). The latter is important in
understanding when animals are within potential strike zones as well as surfacing
intervals.
Photographic Identification/Line Transect Surveys
The methods for tracking and identifying individuals, as well as recognizing their
abundance and distribution is typically conducted during systematic line transect
surveys (see example in figure 3) on large vessels such as SCRIPPS Oceanography’s
and NOAA’s (National Oceanic and Atmospheric Administration), as well as from
small rigid hulled inflatable boats (appox. 5m in length) operating daily from shore
(Calambokidis & Barlow, 2004).
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Figure 3. Line-transect survey lines and sightings of blue whales, 1991–1996. Data reveal that the densest populations
are near-shore central and southern California (Calambokidis & Barlow, 2004).
Photographic identification images are taken with high quality camera and lens systems.
The best ones are chosen and compared to a comprehensive catalogue of previously
identified individuals (example of a photographic identification in figure 4). The
catalogue consists of over 1,000 blue whales that have been identified since 1986
(Cascadia Research
Collective).
Figure 4. Photo identification picture used to track individuals over a period of time. The mottled pattern near the
dorsal fin is used to identify individuals (image provided by Cascadia Research Collective).
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These surveys (Barlow, et al., 1995; Calambokidis & Barlow, 2004) in combination with
long-term photographic identification studies have revealed that the densest blue whale
populations are near the shore in central and southern California (see detailed information
in chapter 3). Though this information is important in understanding the threat of ship
strikes, it still does not reveal insights into the animals’ behavior underwater. To
adequately assess strike potential as a danger, experts are gathering data revealing how
deep animals dive, how long they dive for and what they are doing underwater
(Calambokidis, et al., 2007/08). These pieces of information will help by showing time
spent in or near ship strike zones (Calambokidis, et al., 2007/08).
Bioacoustic Tags
Since 1999 Cascadia Research Collective has been deploying Burgess bioacoustic probes
(bprobes) and video imaging tags (CRITTERCAM) that attach via suction cups (Figure
5) (Calambokidis, et al., 2007/08).
These tags have revealed insights into previously unknown underwater behaviors and
movement patterns (J. Calambokidis, 2003; Calambokidis, Schorr, et al. 2007/08), that
help in understanding ship strike threat potential. Tag data has indicated that (1) blue
whales spend more time at the surface during night hours than during the day; (2) they
surface several times, generally every 5-15 minutes; and (3) they perform lunging feeding
dives at depths of up to 300m (Calambokidis, et al., 2007/08). The latter discovery may
indicate large energetic expenses causing fatigue and disorientation at the initial surfacing
(Calambokidis, et al., 2007/08). Abrupt maneuvering away from a large vessel may not
be an option for a recently surfaced whale.
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Figure 5. Clockwise from top: Burgess Bioacoustic probe deployed on the back of a blue whale off the San Diego
coast in 2002; suction-cup-attached imaging tag (CRITTERCAM); probe attachment method from a rigid hulled
inflatable; (Calambokidis J. , 2003).
Tag Observations of Feeding and Dive Behavior
The output data and results of tags deployed on blue whales in the past decade have
revealed valuable insights into their feeding behavior, group dynamics and vocalizations
(Oleson, Calambokidis, Burgess, McDonald, C., & Hildebrand, 2007; Calambokidis, et
al., 2007/08). Tag deployments were conducted and collected in collaboration with
Cascadia Research Collective, SCRIPPS Institute of Oceanography, Woodshole
Oceanography Institute and Bill Burgess of the Greeneridge Institute. These data have
revealed some information necessary to assess the threat of ship strike potential.
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Lunge dives
Data was gathered during deployments such as those conducted in the Sea of Cortez in
March, 2001 (longest complete record to date) and off of Costa Rica in January, 2008
(Calambokidis, et al., 2007/08). The combined use of sonar depth finders and tag
deployments allowed researchers to find krill layers at specific depths and overlay these
with dive charts from tag-data outputs (Cascadia Research Collective). The output
revealed vertical lunges into krill layers from underneath (figure 6) (Calambokidis J.,
2003). This is important in showing that blue whales feed almost exclusively on krill and
will therefore be attracted to areas hosting dense aggregations of krill such as exist in the
Santa Barbara channel. Furthermore, the density of blue whale populations is higher in
areas hosting this vital food source.
Page 21
Figure 6. Depth on the y-axis and time on the x-axis. Blue whale lunge dives (line graph) into krill layers (cloudy
layering from sonar viewer) from underneath gathered in January 2008 off Costa Rica (Data collected, calibrated and
provided by Cascadia research Collective).
Diurnal Dive Pattern
Several tag deployments (Sea of Cortez 2007, Costa Rica Dome 2008, Southern
California 2002) have revealed a diurnal dive pattern in blue whales (figure 7). This
reaction is most likely due to the vertical migration of krill toward the surface at night
(Calambokidis, et al., 2007/08), though little is known as to why krill migrate vertically
from 250-300m to 0-20m. The whales tend not to feed during the night hours, but travel
at slow speeds, conducting very shallow dives (figure 7: “milling” behavior occurring
from 20:00 – 06:00) (Calambokidis, et al., 2007/08). Regarding ship-whale interactions,
Page 22
this may be an important discovery, as the potential for ship strikes may occur during the
night hours when whales mill near the surface, well within strike depth (Cascadia
Research Collective unpublished data). This potential may be amplified by the lack of
visibility by observers who are unable to detect the animals from traveling vessels
combined with the sleep behavior of the blue whales.
Figure 7. Blue whale dive chart from bioacoustic tag deployment starting at 16:00 and ending at 07:00. Deployed June
2002 off of Southern California. This chart indicates a dramatic diurnal shift in dive pattern, where the animal is
staying closer to the surface after 20:00 (adapted from data provided by Cascadia Research Collective).
Advancement in technology and extensive research efforts have made for a better
understanding of blue whale behavior. With these new discoveries in place, blue whale
conservation efforts such as ship-whale interaction threat assessments can be funded and
researched. The key findings of bio-acoustic probes include:
Page 23
•
Blue whales often approach prey (krill layers) from underneath in vertical lunges,
diving to depths of up to 300m (Figure 6) (Calambokidis, et al., 2007/08).
•
Blue whales have a diurnal dive pattern, where the animals stay close to the
surface during night hours (Figure 7) (Calambokidis, et al., 2007/08).
•
Pairs of blue whales travel together (male-female), but do not engage in
cooperative feeding (Oleson, Calambokidis, Barlow, & Hildebrand, 2007).
•
Only males have been reported (identified via DNA samples from collected tags)
to produce long vocal calls (Oleson, Calambokidis, Burgess, McDonald, C., &
Hildebrand, 2007)
Though helpful in other facets of blue whale research, the latter two points are not
relevant in assessing ship strike threats. The first two points however are important pieces
of the puzzle in attempting to understand the behavior of blue whales that are in close
geographic association with shipping lanes and ship strike zones. The northeast Pacific
stock, most densely aggregated off the Central California coast, has the highest potential
for ship strikes as habitat and vessel traffic overlap. The above mentioned research
methods provided important insights into underwater behavior, but further research and
knowledge is necessary to understand this population’s abundance and specific
distribution.
Page 24
Chapter 3
CURRENT ABUNDANCE ESTIMATES OF NORTHEAST PACIFIC BLUE
WHALES
A Brief on Global Estimates
Blue whales are considered endangered and have been depleted in their range due to
many decades of whaling (Calambokidis, Douglas, Falcone, & Schlender, 2007).
Although the populations of blue whales were severely depleted by whaling, no
evidence is available to suggest that this over-exploitation resulted in a major change in
their distribution. It is assumed that blue whale distribution is governed largely by food
requirements and that populations are seasonally migratory (National Marine Fisheries
Service, 1998). Movements towards the poles in spring allow the whales to take
advantage of high krill production in summer. Movement toward the subtropics in the
fall allow blue whales to reduce their energy expenditure while fasting, avoid ice
entrapment in some areas, and engage in reproductive activities in the warmer waters of
lower latitudes (National Marine Fisheries Service, 1998).
Despite international protection since 1966, the current global population is roughly
estimated at 10,000- 15,000 animals (Barlow, et al., 1995; Gambell, 1976). The global
population is organized into separate “stocks:” (numbers are rough approximations)
7,000-10,000 in the southern hemisphere (this includes the subspecies Pygmy blue whale
B.m.brevicauda), 2,000-3,500 in the Northeast Pacific and 800-1,400 in the north
Atlantic (Mate, Lagerquist, & Calambokidis, 1999, Barlow, et al., 1995). This is only a
Page 25
fraction of the original, pre-whaling global population, which has been estimated at near
350,000 (Gambell, 1976).
Northeast Pacific Population
This population is considered to be one of the largest globally and also one of the ones
most studied (Calambokidis & Barlow, 2004). Due to the proximity of research facilities
as well as their relative proximity to land masses, the northeast Pacific population has
become one of the most documented global stocks. The research presented in this work
will focus its attention to this specific blue whale stock, due to the availability of
information and literature, as well as documented ship strike threats occurring most
frequently within this population.
Photographic identification has revealed that the entire northeast Pacific population
ranges from the Gulf of Alaska to Costa Rica (Calambokidis et al. 2004; Chandler et al.
1999). The population, which feeds off the coast of California from May through
November (Dohl et al. 1983), is considered an independent stock (Barlow, et al., 1995).
They migrate to Mexico and Central America in spring (Calambokidis et al. 1990,
Stafford et al. 1999, Mate et al. 1999, Chandler et al. 1999) and have a size of roughly
1,500-2,000 individuals (Barlow, et al., 1995). Little is understood about the migration
and general North/South movement patterns of this population (Barlow, et al., 1995).
John Calambokidis at Cascadia Research Collective has been conducting extensive
photographic identification of this stock since 1986 and has the best understanding of
their movement and distribution (Bortolotti, 2008). Ship strikes have been reported most
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commonly in this population due to their proximity to land, their dense population and
close association to ship traffic (Cascadia Research Collective unpubl. data; Jensen &
Silber, 2004). Calambokidis et al (2007) reported the abundance and distribution of the
northeast Pacific stock, revealing insights into their geographic association with the
shipping lanes. They present an accurate estimate by (1) obtaining large representative
samples from in- and off-shore waters, (2) comparing 2005 and 2006 survey efforts with
past photographic identification, (3) generating a mark-recapture model from 2004-06
survey efforts and (4) comparing the acquired estimates from three similar abundance
estimates generated over the last 15 years (Calambokidis, Douglas, Falcone, &
Schlender, 2007; Calambokidis & Barlow, 2004). During distribution and data sampling
it is often difficult to avoid bias due to “heterogeneity of ‘capture’ and probability of
geographic sampling partiality” (Calambokidis, Douglas, Falcone, & Schlender, 2007).
This may be introduced by surveying the same or similar regions year after year and
therefore ‘capturing’ the same individuals. For an accurate abundance estimates, a
representative sample of both photographic identification and mark-recapture modeling is
required, as well as covering new areas during surveys (Calambokidis & Barlow, 2004).
Abundance
An abundance report to Southwest Fisheries Science Center (SWFSC) in 2007 utilized
the above described methods and remains the most recent and the most up-to-date report,
covering the years 2004-2006. The methods were similar to those used in past abundance
surveys and the report included all results beginning in 1991 (Calambokidis, Douglas,
Falcone, & Schlender, 2007).
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The combined identifications from both coastal efforts and large vessel surveys represent
the results of this effort (Calambokidis, Douglas, Falcone, & Schlender, 2007). These
estimates show a steady increase from 816 in 1991-93 to 1,428 in 2004-06 (table 1.).
Further, estimates based on all pairs of years regardless of the use of systematic surveys,
generally showed an increase in abundance with the highest years being 2003-06
(Calambokidis, Douglas, Falcone, & Schlender, 2007).
n1 Systematic year
n2 Adjacent years
Period
Year
n1
Years
n2
m
Est.
CV
1991-93
1992
281
1991 &
193
66
816
0.09
368
56
1,190
0.10
449
99
1,291
0.07
388
48
1,428
0.11
1993
1995-97
1996
183
1995 &
1997
2000-02
2001
286
2000 &
2002
2004-06
2005
179
2004 &
2006
Table 1. Summary of mark-recapture estimates for blue whales off California and W. Baja Mexico. Sample n1 consists
of all the identified whales from the year of the SWFSC systematic ship surveys and n2 is from coastal small-boat work
in the adjacent years. The numbers of matches or recaptures are indicated as (m). Coefficients of variation (CV) are
based on analytical formulae. Transcribed from information provided by Cascadia Research Collective (Calambokidis,
Douglas, Falcone, & Schlender, 2007).
Distribution
The Northeast Pacific blue whale distribution data is an outcome of assessing the
abundance of this stock. A visual depiction of this population can be seen in figure 8.
Most of the animals are grouped in the central California to Baja region with some
Page 28
isolated groups in nutrient rich waters off of Costa Rica. It is likely that the waters near
Costa Rica host a small group of blue whale residents year-round. It must be noted in the
image below that no time reference for these observations is given, which may indicate
seasonal shifting.
Figure 8. Southwest Fisheries Science Center publication (2007) on the distribution of Northeast Pacific blue whales
via transect surveys. Image provided by Cascadia Research Collective.
Discussion
All abundance estimates that utilized identification in a year or combination of years
showed fairly strong agreement, both in terms of average values and in patterns of annual
variation (Calambokidis, Douglas, Falcone, & Schlender, 2007). Since samples were not
obtained consistently in the same locations over the years, it may explain some variation
in the pattern of abundance. In the 1990’s there may have been some bias introduced into
the abundance results, as most efforts were focused around the Central California region,
Page 29
which would have resulted in a downward trending abundance estimate (Calambokidis,
Douglas, Falcone, & Schlender, 2007). To reduce the bias rate of heterogeneity of
capture probability Cascadia Research Collective utilized a geographically broad survey
methodology, as well as geographic variation, which may have lowered this bias
(Calambokidis, Douglas, Falcone, & Schlender, 2007).
There is little literature and some controversy surrounding the specific abundance and
distribution of blue whales on the west coast. The difficulties of surveying as well as the
elusive travel patterns of these animals have created a field of limited funding and few
specialists. On the other hand, surveys have consistently revealed (Calambokidis &
Barlow, 2004; Calambokidis, Douglas, Falcone, & Schlender, 2007) that the densest part
of this population of blue whales feed and forage in close proximity to or directly within
areas that host shipping lanes. The Santa Barbara Channel is seen as the “poster child” of
ship strike potential, since it hosts a high volume of ship traffic as well as a dense
population of blue whales.
Chapter 4
SHIP-WHALE INTERACTION ASSESSMENT: The Santa Barbara Channel
The focus of this paper is limited to assessing ship-whale interactions in the Santa
Barbara Channel and its surrounding region. It has been shown (Cascadia Research
Collective, 2007) that incidence of ship strikes on blue whales have occurred on several
occasions in the Santa Barbara Channel. Shipping lane traffic and blue whale feeding
habitat overlap in this region, creating a rich opportunity for investigating a potential
threat to the northeast Pacific stock. A thorough threat assessment in this specific region
Page 30
can be performed and analyzed by understanding blue whale biology, the history of their
decline, study methodologies used and northeast Pacific population distribution and
abundance.
Blue whales are commonly found during the summer and fall season within the Santa
Barbara Channel (Calambokidis, Douglas, Falcone, & Schlender, 2007), as this is a
productive region that supports large concentrations of their primary food source -- krill
(Barlow, et al., 1995). This also happens to be a region hosting shipping lanes for
commercial vessels (see figure 9). The close geographic association between blue whales
and shipping traffic increases the likelihood of whale-ship interactions within this region.
Often, the outcome of a ship strike is fatal, but non-fatal interactions due to close ship
approaches may also be occurring. The potential outcomes of these interactions include
cessation of feeding, interruption of social communication and changes in energetic
expense (Cascadia Research Collective, unpublished data). Though little is known about
blue whale reactions to underwater noise, interactions may be occurring at great distances
due to the input of increased noise into the ocean from ship propellers and machinery
(Calambokidis, et al., 2007/08). Understanding these interactions can inform us as to
how to prevent or reduce the impact of shipping on whale populations.
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Figure 9. Automatic Identification System (AIS) was used to identify ship tracks in commercial shipping lanes in the
Santa Barbara Channel monitored for a 3 month period in 2007. Color indicates direction of travel (image acquired
through Cascadia Research Collective).
Due to increased numbers of blue whale fatalities within this geographic region (6 fatal
blue whale ship strikes in fall 2007), Cascadia Research Collective has recently been
researching this field extensively., The methods combine (1) suction cup acoustic tags,
(2) seafloor acoustic recorders, (3) small boat surveys conducted daily from the coast and
(4) commercial ship traffic details provided by the transmission of Automatic
Identification System (AIS) (information provided by Cascadia Research Collective).
The acoustic data collected by the tag can be used by researchers to determine the
presence of sounds produced by the whales, the noise level prior to ship approach, and
the sound level of the passing ship (Cascadia Research Collective unpublished data).
Further, the sound of the flow noise that the passing water creates, which is generated by
the swimming whale, can be used to provide estimates of swim speed (Calambokidis, et
al., 2007/08). Acoustic recorders placed systematically within the Santa Barbara Channel
may provide measurement of the noise produced by individual ships and overall ambient
noise levels (conducted in collaboration with SCRIPPS Oceanography Institute). AIS
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transmissions provide the vessel’s GPS coordinates, ship length, ship speed and direction
and are recorded at a land-based receiving station in Santa Barbara.
It is crucial to acquire vessel details such as the (1) vessel type, (2) vessel length, (3)
vessel’s speed of travel and (4) vessel’s direction of travel. This information allows for an
adequate assessment of potential ship strike threats. It is important to note though, that
only commercial vessels (e.g.: container/cargo ships, freighters and cruise ships) within
the shipping lanes report via AIS. Other smaller vessels that still have potential for ship
strike threat may be traveling within the feeding and foraging habitat of blue whales
without AIS transmission.
Ship Detail
Vessel Types
Vessels types that travel near and within the shipping lanes and foraging habitat of blue
whales vary greatly. The Large Whale Ship Strike Database (2003) describes the vessels
(134 of 292 incidents with known vessel types) involved in reported strike cases as the
following:
•
17.1% navy vessels
•
14.9% container/cargo ships/freighters
•
14.2% whale watching vessels
•
12.7% cruise ships/liners
•
11.9% ferries
•
6.7% coast guard ships
•
6.0% tankers
•
5.2% recreational vessels and steamships
•
3.0% fishing vessels
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Care must be taken in interpreting these numbers as many ship strikes may be occurring
unnoticed or unreported (Jensen & Silber, 2004). Furthermore, the high incidences of
Navy and Coast Guard vessel strikes may merely be a representation of government and
military standardized reporting practices (Jensen & Silber, 2004).
Vessel Speeds
Only 58 (19.8%) of the 292 reported cases of ship strikes reported their speed (Jensen &
Silber, 2004). The range was from 2-51 knots with a mean speed of 18.1 knots (figure 10)
(Jensen & Silber, 2004).
Figure 10. Frequency of ship strikes in relation to ship speeds of reported cases (Jensen & Silber, 2004)
It has been reported (Jensen & Silber, 2004) that the speed at which a strike causes
serious injury or death is approximately 18.6 knots. Many (67.2%) of the reported vessel
speeds were in the 13-15 knot range, followed closely by 16-18 knot and 22-24 knot
ranges (figure 10) (Jensen & Silber, 2004).
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Ship-Whale Interaction
The total record of past blue whale ship strikes occurring globally is not extensive (table
2). This collection of ship strike data (with the fist one occurring in 1980), were reported
from commercial cargo, military and cruise vessels. It must be considered that these are
merely the ones that were reported. Undoubtedly, more strike events have been occurring
without notice or report, as well as struck whales sinking or floating out to sea. It can
safely be assumed that many more strikes have occurred or are occurring unreported and
unnoticed (Jensen & Silber, 2004).
Date
Location (incl. County)
Sex
08/07/1980
Vandenberg Air Force base, Santa Barbara
Male
08/17/1988
Oceana, San Louis Obispo
Female
08/17/1992
Lompoc, Santa Barbara
No Data
08/02/1993
San Nicolas Island, Ventura
No Data
01/12/1994
Santa Rosa Island, Santa Barbara
Male
08/11/1996
San Miguel Island, Santa Barbara
Female/ Fetus
Table 2. Record of total past ship strikes of blue whales occurring globally, with most documented in the Central
California region (Jensen & Silber, 2004).
Ship Strikes in the Santa Barbara Channel
The Santa Barbara Channel is a productive feeding location for blue whales in the fall
and summer months. As this is also the travel area of commercial ship vessels along the
shipping lanes, ship-whale interactions may be common and threatening for blue whales
feeding and foraging in the area (Calambokidis, et al., 2007/08). Small boat surveys
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conducted daily show a dense abundance of animals in close association with shipping
lanes (figure 11).
Figure 11. Sightings and movements of blue whales in the Santa Barbara Channel, gathered by Cascadia Research
Collective in September 2007 (Provided by Cascadia Research Collective).
In the fall of 2007 six blue whales were reported fatally struck by ships. This was the
largest ship strike event for blue whales on record (Jensen & Silber, 2004). All of the
animals found were in or near Santa Barbara County (figure 12). Table 3 indicates the
detailed summary of the 6 fatalities that occurred in a series of the most dramatic ship
strike events to date (Jensen & Silber, 2004).
Whale 1
Date
09/09
Whale 2
Whale 3
09/11
09/12
Whale 4
Whale 5
Whale 6
09/19
09/20
11/29
Location
Long Beach
Harbor
Hobson Beach
San Clemente
Is.
N Baja, Mexico
Pt. Mugu
San Miguel Is.
Gender
Male
Length (feet)
72
Female
No Data
79
No Data
No Data
Male
Female/ Fetus
No Data
70
72/13
Table 3. Summary of deceased blue whales in fall 2007
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Figure 12. Locations of deceased blue whales in the fall of 2007 (details included in table), adapted from data
provided by Cascadia Research Collective. Map Credit: Channel Islands National Marine Sanctuary (CINMS)
Causes of Injury or Death
Jensen and Silber (2004) reported 292 ship strike occurrences on large cetaceans. Of
these, 48 resulted in injury and 198 resulted in fatality (Jensen & Silber, 2004). Though in
many cases the fate of a struck whale is unknown (39 of the 292 cases), these data
indicate that of the 292 reported ship strikes, 246 incidents showed evidence of a shipwhale interaction where animals were injured or killed (Jensen & Silber, 2004).
It is sometimes difficult to tell if an animal found dead was killed via ship strike ante- or
post-mortem. Jensen and Silber (2004) included those cases that showed strong
likelihood of ship strike evidence, which included propeller marks, bruising,
hemorrhaging and severed flukes. Further, if a whale was found floating (blue whales
float ventral side up, post-mortem) with no ship-strike marks showing ventrally, it can be
assumed that if marks on the dorsal side indicated ship strike, the animal was killed antemortem (Jensen & Silber, 2004).
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Necropsies and visual evidence indicate that the cause of death or injury is due either to
blunt force trauma or propeller wounds (Cascadia research unpublished data). The blunt
trauma is caused by the bulbous bow (figure 13) that freighters and other large ships
have.
Figure 13. The combination of a bulbous bow and the fast speed of a large vessel increase the potential for ship
strike fatalities.
Population Threat
No published literature has reported that ship strikes are causing harm or decline to blue
whale populations. Cascadia Research Collective and other experts in the field are
continuing to gather the data necessary to publish the details of this risk to blue whales.
The data that has been collected so far (Cascadia Research Collective; June, July, August,
September of 2007 and 2008), in combination with past published studies (Douglas,
Calambokidis, Raverty, Jefferies, Lambourn, & Norman, 2008; Jensen & Silber, 2004;
Calambokidis, Douglas, Falcone, & Schlender, 2007, Calambokidis, et al., 2007/08) is
adequate enough to make an assessment of potential threat to blue whale populations.
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Though blue whales travel most of the world’s oceans, there is not enough data reporting
ship strikes to make an assessment of the global context. It can only be assumed that ship
strikes may occur where blue whale feeding habitat and commercial shipping lanes
overlap. As this is a new field, focus must be turned to those areas that have been
documented and studied more heavily than others (e.g.: Central California region).
It has been documented that a dense population of blue whales (1,428 animals for 200406 from central California to Baja Mexico) feed and forage in the Santa Barbara Channel
region during the summer and fall months (chapter 2) (Calambokidis, Douglas, Falcone,
& Schlender, 2007). This is also where commercial ships (e.g.: cargo, oil tankers, cruise
liners: see chapter 4) travel. Past blue whale ship strike records have shown that most
have occurred in the Central California region (Jensen & Silber, 2004 Cascadia Research
unpublished data, 2007). In the fall of 2007 the biggest recorded fatal strike event of six
animals occurred in the Central California region (Santa Barbara Channel) (Cascadia
Research unpublished data, 2007). Blue whales, though long lived (30-80 years), have a
relatively low reproductive output (approximately 2-20 offspring per lifetime).
Furthermore, this is in relation to a population decline of approximately 90% from six
decades of whaling (original numbers estimated at 9,000 animals in the northeast Pacific)
(chapter 1) (Bortolotti, 2008; Ellis, 1991; Jackson, 1978; Gambell, 1979), which has
made the species endangered and vulnerable.
The combination of these factors shows conclusive evidence that ship strikes are a
considerable threat to blue whales. Though no long-term data (>5 years) exists of ship
strikes causing blue whale populations to slow in growth or decline, the potential exists.
For a species as threatened and as slow growing as blue whales, all conservation efforts
Page 39
are critical. Blue whales are being struck seasonally on a regular basis (Cascadia
Research Collective unpublished data, 2007; Jensen & Silber, 2004) in areas of feeding
habitat overlapping ship traffic. To continue to assess the threat of ship strikes and take
necessary measures and precautions to reduce long term impacts is an important tactic in
the future of blue whale conservation.
Chapter 5:
FUTURE BLUE WHALE STUDIES AND POSSIBLE CONSERVATION
STRATEGIES
Blue whales have suffered many decades of decline and the global population is now
only at a fraction of what it was before the whaling era. Though practically no blue
whales have been intentionally killed by humans since the 1970’s, populations are not
showing signs of recovery. Other whale species that were heavily hunted have bounced
back since they were declared endangered. Sperm whales for example, were hunted for
nearly two centuries until 1986 when the IWC put a ban on their catch (Ellis, 1991). They
are now off the endangered species list and populations are estimated as high as 400,000
animals worldwide. Fin whales, the closest relative to the blues, were whaled in large
numbers: more than 700,000 in the Antarctic alone (Ellis, 1991). Though still only a
fraction of these numbers exist in southern waters, they are abundant in the northern
hemisphere and today are no longer considered endangered (Bortolotti, 2008). Whale
populations typically increase once hunting has stopped, but the rate of recovery varies
Page 40
with the animal’s biology and interaction with human activity. What is it about blue
whales that will not allow their populations to bounce back to their abundance of the
past?
Blue whale reproductive strategy aside, there are unknown reasons as to why populations
are not recovering like experts had hoped. Because of these unknown factors,
conservation efforts are an important tool in the long-term recovery of blue whale
populations. It has been shown that the blue whale only faces one natural predator: the
killer whale (Jefferson, Webber, & Pitman, 2008). Though attacks have been
documented, these are rare and do not cause enough deaths to account for declining blue
whale populations. Ship strikes have been documented as the main anthropogenic factor
potentially causing harm to blue whale populations. A high priority for research
organizations is investigating ship-whale interactions as a conservation threat to the
northeast Pacific stock (Cascadia Research Collective unpubl. Data). For the prevention
of fatal ship strikes, much more analysis, planning and research is necessary.
Unknowns
There is much difficulty in determining long term human impacts on blue whale
populations. Though the threat assessment of ship strike potential on blue whales is a
high priority, many unknown variables still exist (Cascadia Research Collective unpubl.
data). Understanding these is the first step in realizing the specific aspects of research that
need to be undertaken. Presently it is not possible to determine (1) the true number of
ship strikes occurring on blue whales. Many struck animals go unnoticed by large vessels
or do not get reported for fear of negative consequences. Furthermore, struck animals
Page 41
may simply sink or float out to sea. The lack of understanding of strike events is a
symptom of (2) not knowing exactly when, where and in what situations ship strikes are
occurring. Because many events go unnoticed it is difficult to find a trend to determine
which locations yield high strike potential. Presumably risk is highest where foraging and
feeding habitat overlap with dense ship traffic. In areas where shipping lanes and feeding
habitat of whales overlap, close encounters occur frequently as well. It is therefore
important to understand (3) how blue whales react or do not react to an approaching ship.
This aspect of research will allow researchers to understand the factors that cause large
ships to strike such fast swimming whales. Ship-whale interactions may be causing
selective pressures that influence distribution and behavior. It is important to determine
(4) how the resulting behavioral and distributional shift can be predicted. These as yet
unknown factors are reasons why strike events are currently a threat to blue whales.
Continued research efforts can play a vital role in preventing further ship strikes.
Continued Research
The best method for understanding the long-term population impacts of ship strikes on
blue whales is continued research efforts. As noted in Chapter 3, research efforts are
underway to further understanding of blue whale behaviors, their feeding ecology and
their reproductive strategies. In regards of ship-whale interactions, an underlying research
effort that can help provide useful large-scale data is (1) the continued monitoring of the
overall distribution and abundance of blue whales (as seen in chapter 2). Another aspect
that can shed light on this complicated field is focusing attention on areas of known close
encounters of ships and whales (e.g.: Santa Barbara Channel, California; discussed in
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chapter 3). It is particularly in this arena that (2) the studies of blue whale underwater
behavior in shipping lanes and their reaction to closely traveling ships offer a rich and
valuable area for research. Research organizations have undertaken this by going in small
(<5m), rigid hulled inflatable boats into the Santa Barbara channel and surveying and
monitoring blue whales, while logging all ships in the area, and noting all close
encounters (Cascadia Research Collective unpubl. Data). Along these lines, it is
important to (3) monitor ship traffic. In particular, focus should be placed on those areas
where blue whales feed and forage. This, as seen in chapter 3, will show vessel
movement trends in particular areas, and allow for an assessment of higher and lower risk
locations. To get a clearer idea of what the causes of ship-whale interactions are, (4)
acoustic studies of whales and ships are also essential elements. Researchers have little
understanding of the hearing physiology and mechanisms of blue whales, as well as what
type of frequencies may cause reactions. Studying both the acoustic behavior of blue
whales and the sound emissions of traveling vessels will help shed light on the factors
causing ship strikes. As seen through past events (chapter 4), ship strikes cannot be
foreseen. However, once a ship strike event has occurred and a blue whale carcass is
inspected, much data can be extrapolated. It is therefore important to (5) plan and prepare
for strandings in advance before the animal decays, sinks, or drifts off to sea. To
accommodate important future studies it will be necessary to (6) develop an integrated
monitoring plan specifically for blue whale ship strike events.
Possible Strategies to Avoid Ship Strikes
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The North Atlantic Right Whale is a highly endangered baleen whale species that has
faced detrimental population effects due to ship collisions. Recently (2008) a law was
passed to slow ship speeds, which allows the animal time to maneuver out of potential
strike zones. A strategy for lowering the threat of ship strikes on blue whales in the Santa
Barbara Channel could be (1) adjusting ship speeds (to10 knots) considering temporal,
geographic and seasonal conditions. Further, since blue whales have relatively short dive
times (5-15 minutes), large blow plumes, and enormous body sizes, they may be easily
detectable from great distances. Another strategy may therefore be (2) to place observers
on ships where blue whales frequently occur within close proximity to shipping lanes. As
seen in September 2007 (chapter 4), the high density of blue whales in the Santa Barbara
Channel along with the close proximity of shipping lanes can have detrimental effects. To
prevent a strike event like the one in fall 2007 from reoccurring, (3) adjusting shipping
lanes may be a useful option. These adjustments don’t necessarily need to be permanent.
Important aspects to consider are temporal and seasonal variability, areas of feeding and
foraging habitats, and regions where blue whales are consistently abundant, such as the
Santa Barbara Channel. During seasonal variations, shipping lanes can be shifted within
the channel or moved outside the channel. Since blue whale research in these areas is
constantly being undertaken by researchers a helpful tactic would be to (4) provide
abundance and distribution data of whale sightings to the shipping industry in a timely
fashion. This can help the industry take necessary precautions and has potential to
prevent further ship strikes.
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