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Environ Biol Fish (2010) 88:361–368
DOI 10.1007/s10641-010-9649-2
Author's personal copy
Foraging ecology of Cookiecutter Sharks (Isistius brasiliensis)
on pelagic fishes in Hawaii, inferred from prey bite wounds
Yannis P. Papastamatiou & Brad M. Wetherbee &
John O’Sullivan & Gwen D. Goodmanlowe &
Christopher G. Lowe
Received: 22 July 2009 / Accepted: 7 April 2010 / Published online: 21 April 2010
# Springer Science+Business Media B.V. 2010
Abstract The Cookiecutter Shark (Isistius brasiliensis)
is an ecto-parasitic predator of numerous large pelagic
fish and mammals. However, little is known of its
foraging ecology due to its elusive foraging tactics in
the pelagic environment. We used bite scar patterns on
pelagic fishes landed at the Honolulu Fish Auction to
assess some of the Cookiecutter Shark foraging habits.
Swordfish (Xiphias gladius) had the greatest percen
tage of bites (87.9±25.0% of individuals had healed
scars) followed by Opah (Lampris guttatus, 33.0±
8.3% of individuals). Most fish with scars only had one
Y. P. Papastamatiou (*)
Hawaii Institute of Marine Biology,
University of Hawaii at Manoa,
46-007 Lilipuna rd,
Kaneohe, HI 96744, USA
e-mail: ypapastamatiou@gmail.com
B. M. Wetherbee
Department of Biological Sciences,
University of Rhode Island,
100 Flagg Rd,
Kingston, RI 02881-0816, USA
J. O’Sullivan
Monterey Bay Aquarium,
886 Cannery Row,
Monterey, CA 93940, USA
G. D. Goodmanlowe : C. G. Lowe
Department of Biological Sciences,
California State University Long Beach,
1250 Bellflower Blvd.,
Long Beach, CA 90840, USA
Cookiecutter Shark bite per individual with the
exception of Swordfish, which often had >5 bites per
individual. Furthermore, Swordfish had a higher
proportion of healed bite scars meaning they had been
attacked while free-swimming. Seasonal changes in the
probability of hooked fish being bitten by sharks were
apparent for Swordfish, Bigeye Tuna and Opah. Based
on bite scar diameter, larger Cookiecutter Sharks may
preferentially attack Swordfish rather than the other
species of pelagic fish. When taken in conjunction with
diving behavior of pelagic fish, and fishing depths, the
results add further support to the hypothesis that
Cookiecutter Sharks perform diel vertical migrations.
Keywords Cookiecutter Shark . Longline fishery .
Opah . Predation . Swordfish
Introduction
The Cookiecutter Shark (Isistius brasiliensis) is a
small squaloid shark found in the pelagic waters of
tropical and sub-tropical oceans (Jahn and Haedrich
1987; Nakano and Nagasawa 1996; Compagno et al.
2005). Cookiecutter Sharks feed on cephalopods, but
also have a unique parasitic foraging strategy which
enables them to prey on animals much larger than
themselves. Cookiecutter Sharks have a collar of
pigmented cells just posterior to the head, surrounded
on either side by luminous photophores, which are
362
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thought to act as a lure for large upward-looking
visual predators (Widder 1998). The shark’s unique
mouth, teeth and tongue morphology then allows it to
remove a circular plug of tissue from the larger
animal (Jones 1971; Shirai and Nakaya 1992). As
such, Cookiecutter Sharks are able to prey on or bite a
wide variety of pelagic fishes (Jones 1971; MuñozChápuli et al. 1988), whales (e.g. Evans et al. 2002;
McSweeney et al. 2007) seals (e.g. Le Boeuf et al.
1987; Hiruki et al. 1993), and even submarines and
oceanographic equipment (Johnson 1978). Cookiecutter Sharks have been caught as deep as 3,800 m,
although most are caught at shallower depths,
particularly in surface trawls at night, leading to the
hypothesis that these sharks perform diel vertical
migrations (Jahn and Haedrich 1987; Le Boeuf et al.
1987; Nakano and Tabuchi 1990; Compagno et al.
2005). Other than these basic observations, very little
is known about Cookiecutter Shark foraging ecology
or behavior.
Due to it being rarely encountered by humans, its
small size, and pelagic and elusive nature, one of the
few available methods used to study Cookiecutter
Shark foraging ecology is through the patterns and
frequency of bite scars on prey animals. Fresh bites
on Swordfish caught in the longline fishery were used
to quantify the distribution of Cookiecutter Sharks in
the North Eastern Atlantic, as well as look for
evidence of shark size segregation (Muñoz-Chápuli
et al. 1988). To date, no other studies have used bite
scars on pelagic fishes to make inferences on the
foraging ecology of Cookiecutter Sharks. In the 1980s
a large pelagic longline fishery developed off the
Hawaiian Islands for Swordfish and tunas. In addition, there are numerous local fishers that commercially land pelagic fishes caught around the main
Hawaiian Islands, at the Honolulu Fish Auction, one
of the largest public fish auctions in the world.
Understanding the foraging ecology of Cookiecutter
Sharks can have economic implications as the bites
inflicted by sharks on pelagic fish can lower the
market value (B. Takenaka, manager of the Hawaii
Fish Auction, pers. comm.).
We conducted weekly surveys of the Hawaii
Fish Auction on Oahu, Hawaii to examine the
patterns of bite scars on pelagic fishes. Our goals
were to 1) quantify seasonal changes in bite scars
on pelagic fishes, 2) quantify species specific
differences in the frequency and patterns of bite
Environ Biol Fish (2010) 88:361–368
scarring on pelagic fishes, 3) use bite diameter to
estimate the size of Cookiecutter Sharks attacking
different pelagic fishes, 4) make inferences on the
foraging ecology of Cookiecutter Sharks from bite
scarring patterns.
Methods
We visited the Honolulu fish auction weekly from
February 2007 until February 2008 to examine
pelagic fish brought in by the longline fleets. The
surveys of the fish auction were conducted at
06:00 h on the same day each week, to standar
dize the sampling regime. We counted the number
of fish of each target species on the auction floor
and determined what percentage of fish had
Cookiecutter Shark bite scars. We then selected a
sub-sample of ten individuals for each species to
make a more detailed examination of bite patterns.
Fish are laid out on pallets, so we sampled fish in
order along the floor to prevent sampling bias. For
the sub-sampled fish, we determined the number
of bites, diameter of each bite, and scar stage. Scar
stage was classified as follows: 1 (fresh bite—deep
crater wound with no indication of new tissue
formation), 2 (partially healed—crater wound shal
low and membrane and tissue formation started),
and 3 (healed scar—crater wound filled in with
new tissue leaving just a dermal scar) (Fig. 1).
Based on their high annual occurrences, the following species were selected for counts: Swordfish
(Xiphias gladius), Bigeye Tuna (Thunnus obesus),
Fig. 1 Photo of Cookiecutter Shark bites on Swordfish at
various scar stages. Includes fresh bites (stage 1), partially
healed (stage 2) and fully healed bites (scale 3)
Environ Biol Fish (2010) 88:361–368
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Yellowfin Tuna (Thunnus albacares), Skipjack Tuna
(Katsuwonus pelamis), Sickle Pomfret (Tarac
tichthys steindachneri), Opah (Lampris guttatus),
Wahoo (Acanthocybium solandri), Pacific Blue
Marlin (Makaira mazara), Striped Marlin (Tetra
pturus audax), and Shortbill Sailfish (Tetrapturus
angustirostris). Fish are arranged on one of their
sides along the auction floor, which means that
counts of bites were only of one side. All fish sold
at the Honolulu fish auction are required to be
presented with bite marks or scars facing upward.
As such, all estimates of counts and frequency are
perhaps an under-estimate of predation rates by
Cookiecutter Shark.
We determined seasonal changes in the number of
bites, and scar stage for each species. We used oneway ANOVA’s with Tukey-Kramer aposteriori tests,
to examine seasonal and species differences in bite
rates. All data were arcsine squareroot transformed
before statistical testing. Further testing was done for
the four species with the highest frequencies of
Cookiecutter Shark bites, and largest sample sizes:
Swordfish, Opah, Bigeye and Yellowfin Tuna. For
each month, we determined the probability that a
particular species would be bitten by a Cookiecutter
Shark while on the longline. For each species we
determined the frequency of fish with fresh scars
(bite scar stage 1), and calculated the probability (P)
of a fish on a longline being bitten, based on a
binomial distribution, P ¼ 1 ð1 f Þ2 , where f is
the frequency of fish with fresh bites. We also
calculated the probability that a free swimming
fish would be attacked by a Cookiecutter Shark,
based on the frequency of stage 2 and 3 bite scars
combined throughout the year (i.e. not differentiated seasonally). We estimated the size of sharks
that inflicted bites on pelagic fish from the
diameter of bite scars, by using the Cookiecutter
Shark mouth width (MW)-total length (TL) regression, TL ¼ 4:51ðMWÞ þ 82:8, where TL is shark
total length (mm) and MW is shark mouth width
(mm), as described by Cadenat and Blache (1981, in
Muñoz-Chápuli et al. 1988).
This project required certain assumptions that
included 1) all crater wounds were inflicted by I.
brasiliensis, 2) for fresh bites, the bite was inflicted
while the fish was on the long-line, and 3) bite
diameter of fresh scars corresponds with shark mouth
diameter.
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Results
We conducted 51 weekly surveys of the Honolulu fish
auction where we surveyed a total of 15 107 fishes.
The largest numbers of fish counted were for Bigeye
Tuna, followed by Sickle Pomfret, Yellowfin Tuna,
and Opah (Fig. 2a). There were clear differences in
the percentage of fish with fresh Cookiecutter Shark
bites, between the species (ANOVA: F8, 99 =7.15,
p < 0.0001; Fig. 2a). Swordfish had the highest
percentage of fresh bites with 16.9±15.6% (±1 SD)
of fish having scars, followed by Opah (13.9±10.5%;
Fig. 2a). There were no significant differences
between the other species (range fresh bites
1.7–3.4%). Pacific Blue Marlin were the only species
surveyed for which no bites were observed (429
individuals). There were also clear species specific
differences in the percentage of fish with old healed
scars (ANOVA: F8, 99 =45.85, p<0.0001; Fig. 2b).
Again, Swordfish (87.9±25.0%, probability 0.97),
and Opah (33.0±8.3%, probability 0.44) had the
greatest percentage of bites, while there were no
differences between the other species (range old scars
0–6%). The exception was for Sickle Pomfret,
Skipjack Tuna, and Blue Marlin, all of which had
significantly lower frequencies of healed scars than
the other species (Fig. 2b).
For the three species with ranked percentage with
bites, there were no obvious seasonal changes in the
percentage of fish with bites. Swordfish (ANOVA:
F11,39 =1.49, p=0.17), Bigeye Tuna (ANOVA: F11,39
=0.84, p=0.60) and Opah (ANOVA: F11,39 =1.97,
p=0.06), had relatively consistent bite scar frequencies throughout the year (Fig. 3). The decline in
Swordfish on the auction floor from August–December was due to longline quotas having been met,
hence much smaller sample sizes during those
months. However, when looking at the probability
of these three species having fresh bites (scar stage 1),
some seasonal patterns appeared (Figs. 3, 4). For
Opah and Bigeye Tuna, the probability of being bitten
was highest in February and March and October–
December, while the lowest probability occurred
during January (Fig. 4a, c). For Swordfish, the
probability of a fish being bitten peaked in May
(0.68), after which there was a linear decrease until
September (probability 0, r 2 = 0.97, F = 143.9,
p = 0.0006) and only an increase in December–
January (probability 0.36, Fig. 4b). Again, however,
shallow-night sets
Environ Biol Fish (2010) 88:361–368
A
swordfish
a(354)
striped marlin
b(465)
sailfish
b(539)
blue marlin
b(430)
wahoo
b (714)
skipjack
deep-day sets
Fig. 2 Percentage of fish
with fresh (a) or healed (b)
Cookiecutter Shark bites.
Pelagic fish are listed
vertically to correspond
with the depth at which fish
are caught (Swordfish
caught shallow at night
down to Bigeye Tuna
caught deep during the day).
Error bars are standard
deviations. Bars with the
same letter are statistically
the same. Numbers in
parenthesis in (a) represent
sample size, while those in
(b) are the probability of a
free swimming fish being
bitten, based on a binomial
distribution
Author's personal copy
b(666)
yellowfin
b(1305)
sickle pomfret
b(1737)
opah
a(977)
bigeye
b(7920)
0
10
20
30
40
50
Percentage fresh bites
B
a (0.97)
swordfish
striped marlin
b (0.03)
sailfish
blue marlin
b(0.04)
c (0)
wahoo
b(0.06)
skipjack
deep-day sets
c(0.01)
yellowfin
b(0.11)
c(0.01)
sickle pomfret
opah
d(0.52)
bigeye
b(0.06)
0
20
40
60
shallow-night sets
364
80
100
120
Percentage old bites
probability values calculated in September–December
were based on smaller sample sizes than other
months.
The majority of fish only had one Cookiecutter
Shark bite, particularly Skipjack Tuna where no fish
had >1 bite (Fig. 5). Sickle Pomfret (7%), Shortbill
Sailfish (15%), Opah (20%), Bigeye Tuna (7%),
Yellowfin Tuna (12%), and Swordfish (62%) had
appreciable numbers of individuals with 2 bites. The
only species with significant numbers of individuals
with >2 bites were Swordfish, where 5% of fish had
>5 bites per individual (Fig. 5).
We estimated that the Cookiecutter Sharks that
inflicted wounds on pelagic fish ranged in size from
13 cm to 53 cm TL (Fig. 6b). However, Swordfish
tended to have larger bite wounds than the other
species, suggesting that they were attacked by larger
sharks (Fig. 6a). Estimated shark size preying on
Swordfish (34.1±7.9 cm), were larger than for Bigeye
Tuna (29.5±6.7 cm), Opah (27.2±7.0 cm) or Yellowfin
Tuna (28.4±5.9 cm, ANOVA: F3, 411 =12.9, p<0.0001;
Fig. 6a).
Discussion
The Cookiecutter Shark is clearly a versatile pelagic
predator as indicated by the large variety of pelagic
fish with wounds. In addition to the fish sampled,
other species on the auction floor all have been seen
Environ Biol Fish (2010) 88:361–368
Fig. 3 Seasonal changes in
the number of fresh,
partially healed, and fully
healed bites for Swordfish,
Bigeye Tuna and Opah.
Numbers above bars are
sample size
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# of fish with bites
# of fish with bites
60
50
Swordfish
144
40
Fresh bites
Partially healed bites
Healed bites
39
30
30
41
20
28
30
16
5
10
0
60
50
Bigeye 571
40
30
3
5
3
788
896
815
999 647 712
556
482
345
1
603
506
20
10
0
60
# of fish with bites
365
50
Opah
196
130
111
40
30
20
67
89
35
123
83
51
37
28
10
27
0
Feb
0.8
opah
0.6
0.4
0.2
0.0
Probability
0.8
swordfish
0.6
0.4
0.2
0.0
0.10
bigeye
0.08
0.06
0.04
0.02
0.00
Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Jan
Month
Fig. 4 Seasonal changes in the probability of fish receiving
fresh Cookiecutter Shark bites for Swordfish, Opah and Bigeye
Tuna
Mar
Apr
May
Jun
Jul
Aug
Sept
Oct
Nov
Dec
Jan
with Cookiecutter Shark scars, including Dolphin
Fish (Coryphaena hippurus), Oil Fish (Ruvettus
pretiosus) and various species of shark (Y. Papastamatiou, pers. obs.). In Hawaiian waters, whales and
seals are also seen with Cookiecutter Shark bite scars
(Hiruki et al. 1993; McSweeney et al. 2007), and
Hawaii is also the location of the first documented
Cookiecutter Shark attack on a human swimmer (G.
Burgess, International Shark Attack File, pers. comm.).
However, there were clear differences in the degree of
predation on the various species of pelagic fishes.
Differences in bite scar frequencies between
pelagic fishes are going to be related to both the
behavior of fish prey, the behavior of Cookiecutter
Sharks, and the characteristics of the longline fishery
which targets the different species. Analysis of the
longline fisheries reveals that in general, sets that
catch Swordfish are predominantly set at night, in
shallow water (median depth of 60 m), and 70% are
caught outside the Hawaiian Exclusive Economic
Zone (EEZ) (extending up to 45°N; He et al. 2006;
Bigelow et al. 2006, PIFSC log book report 2007).
Tunas and other fishes including Wahoo, Opah, and
Sickle Pomfret, tend to be caught on sets in deeper
water (median depth of 268 m), set during the day,
and almost 70% are within the Hawaiian EEZ
(Bigelow et al. 2006; He et al. 2006; PIFSC log book
report 2007). Swordfish and Opah had the highest
percentage of fresh bites, most of which were
366
Fig. 5 Species specific differences in the number of
cookie cutter bites per
individual
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Environ Biol Fish (2010) 88:361–368
skipjack
striped marlin
wahoo
1 bite
2 bites
3 bites
4 bites
5 bites
> 5 bites
bigeye
sickle pomfret
yellowfin
sailfish
opah
swordfish
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Proportion of fish with bites
presumably inflicted while the fish were hooked on
the longlines. When taken in conjunction with the
characteristics of the fishery, our data further supports
the hypothesis that Cookiecutter Sharks are diel
vertical migrators, occupying deeper depths during
the day, and moving close to the surface at night (Le
Boeuf et al. 1987; Nakano and Tabuchi 1990;
Compagno et al. 2005). Although there were no
seasonal shifts in the number of fish with scars, there
did appear to be some seasonal changes in the
probability of hooked Swordfish, Bigeye Tuna, and
Opah, being bitten by Cookiecutter Sharks. These
changes in bite probabilities could indicate some
degree of north-south seasonal migration of Cookiecutter Sharks during the winter months. However,
the small winter sample sizes, and the fact that we do
not know exact capture locations of fishes, means that
presently the seasonal migration is little more than a
hypothesis.
Healed scars were almost certainly bites that were
inflicted on free-swimming prey. When examining the
percentage of fish with healed scars, and species with
>1 bite per individual, Swordfish have the greatest
probability of being bitten while free-swimming,
followed by Opah. The vertical diving behavior of
these two species, consist of deep dives during the
day (100–600 m), and shallower dives (0–150 m) at
night (Carey and Robison 1981; Polovina et al. 2008).
These depths are considerably deeper than the habitat
used by Blue Marlin, Striped Marlin and Yellowfin
Tuna, all of which rarely dive below the mixed layer,
which in Hawaii is typically less than 100 m depth
(Holland et al. 1990; Brill et al. 1993, 1999), and may
further reflect the diel vertical migratory behavior of
Cookiecutter Sharks. However, Bigeye Tuna also use
deeper habitats (e.g. Dagorn et al. 2000), but are
targeted less frequently by sharks than Swordfish or
Opah, so some other factors must also influence
species specific foraging rates. Characteristics of
dermal tissue may also influence predation rates, as
no bite scars were found on any Blue Marlin specimens. Unlike the other species, Blue Marlin have
characteristic thick, thorny scales which may make it
difficult for Cookiecutter Sharks to successfully re
move a plug of tissue. Overall, the probability of freeswimming pelagic fishes being bitten by Cookiecutter
Shark was fairly low.
Finally, there may be some evidence of prey size
selection by Cookiecutter Sharks, as larger bites were
recorded on Swordfish than for any other pelagic fish
species. This could be indicative of size or sex
selection/segregation. For example, male Cookie
cutter Sharks are rarely found in excess of 40 cm
Total Length (TL), while females reach up to 51 cm
TL (Jahn and Haedrich 1987; Nakano and Tabuchi
1990, Compagno et al. 2005). Over 14% of bites on
Swordfish were made by sharks >40 cm TL, while
only 3% of Opah, Bigeye and Yellowfin Tuna bites
were from sharks >40 cm. Therefore, a higher
proportion of bites on Swordfish may have been
inflicted by female sharks. Fishing records from
trawling, and bite scar patterns have also suggested
some degree of horizontal sex and size segregation of
Cookiecutter Sharks (e.g. Muñoz-Chápuli et al. 1988;
Nakano and Tabuchi 1990). However, the mechanical
properties of the tissue of pelagic fishes are unknown;
and it is also possible that Swordfish skin stretches
more after being bitten by equally sized sharks,
Environ Biol Fish (2010) 88:361–368
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367
a
50
Estimated shark size (cm)
a
40
b
b
b
opah
yellowfin
30
20
10
0
swordfish
bigeye
b
0.6
swordfish
bigeye tuna
opah
yellowfin tuna
0.5
Proportion
0.4
0.3
0.2
0.1
0.0
10
20
30
40
50
60
70
Estimated shark size (cm)
Fig. 6 a Predicted sizes of cookiecutter sharks that inflicted
bites on Swordfish, Opah, Bigeye and Yellowfin Tuna. Error
bars are standard deviation; bars with the same letter are
statistically identical to each other. b Frequency histogram of
the size range of Cookiecutter Sharks inflicting bites on pelagic
fishes
thereby giving the appearance of larger shark bites. It
is also unknown if there are species specific differences in healing rates, or if scars may eventually
disappear altogether.
The low abundance, oceanic habitat use and elusive
nature of Cookiecutter Sharks, requires us to use indirect
methods to quantify their foraging behavior. Yet despite
the numerous assumptions, this study provides insight
into the foraging ecology of this elusive species. The
data presented provides new hypotheses of Cookiecutter
Shark behavior and also provides quantitative information on which pelagic fish are targeted and when. Future
studies should investigate the economic impacts of
Cookiecutter Sharks on the pelagic fisheries, and
obviously, should a source of live animals present itself,
attempt to quantify in situ behavior to test these
hypotheses.
Acknowledgements We would like to thank B. Takenaka for
providing us with continuous access to the Honolulu fish
368
Author's personal copy
auction. We would like to thank J. Dale, N. Whitney, and L.
Davis for helping with auction sampling. Finally, we would
also like to thank J. McCosker and two anonymous reviewers
whose comments improved the manuscript. This is a contribu
tion of the MBA/HIMB Collaborative Research Program.
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