Records of white shark, Carcharodon carcharias, in the Gulf of California, Mexico

Abstract

The white shark is known to inhabit the Gulf of California, but few published records exist for the most frequent localities of captures or sightings of this protected and relatively uncommon shark in Gulf waters. We have compiled and here report 38 records of white shark captures and reliable sightings for the Gulf. Records include individuals caught as by-catch by shrimp trawlers and gill-nets, and several sightings by divers or at fishing camps with corroborating photographs or sets of jaws (teeth). The main locations of occurrence were El Golfo de Santa Clara (13 records), followed by Santa Rosalía (4), and San Pedro Mártir and San Pedro Nolasco Islands (3 each). Presence of juveniles (<300 cm total length) was highest from January to May (10 records); whereas in July and October only two juveniles were recorded. Adults were more common from December to May (8 records); whereas from June to October there were fewer (5). Human induced threats and conservation of the white shark in the Mexican Pacific are briefly discussed.

Full text

Records of white shark, Carcharodon
carcharias, in the Gulf of California, Mexico
felipe galva
’n-magan
~a
1
, edgar mauricio hoyos-padilla
1
, carlos j. navarro-serment
2
and fernando ma
’rquez-fari
’as
3
1
Centro Interdisciplinario de Ciencias Marinas, Apartado Postal 592, CP 23000, La Paz, Baja California Sur, Me
´xico,
2
Onca Maya
A.C. Playa Copacabana #3049, Col. Primavera, CP 64830, Monterrey, Nuevo Leo
´n, Me
´xico,
3
Facultad de Ciencias del Mar,
Universidad Auto
´noma de Sinaloa, Paseo Claussen s/n, Apartado Postal 610, Mazatla
´n, Sinaloa, CP 82000, Me
´xico
The white shark is known to inhabit the Gulf of California, but few published records exist for the most frequent localities of
captures or sightings of this protected and relatively uncommon shark in Gulf waters. We have compiled and here report 38
records of white shark captures and reliable sightings for the Gulf. Records include individuals caught as by-catch by shrimp
trawlers and gill-nets, and several sightings by divers or at fishing camps with corroborating photographs or sets of jaws
(teeth). The main locations of occurrence were El Golfo de Santa Clara (13 records), followed by Santa Rosalı
´a (4), and
San Pedro Ma
´rtir and San Pedro Nolasco Islands (3 each). Presence of juveniles (,300 cm total length) was highest from
January to May (10 records); whereas in July and October only two juveniles were recorded. Adults were more common
from December to May (8 records); whereas from June to October there were fewer (5). Human induced threats and conserva-
tion of the white shark in the Mexican Pacific are briefly discussed.
Keywords: white shark, Carcharodon carcharias, by-catch, sightings, Gulf of California
Submitted 16 May 2010; accepted 6 September 2010
INTRODUCTION
The white shark, Carcharodon carcharias, is generally known
as a coastal and offshore species, usually found close to conti-
nental and insular shelves in temperate and sub-tropical seas.
However, it has also been recorded oceanically (transiting
individuals) and occurs in the equatorial tropics as well
(Klimley & Ainley, 1996). Its distribution in the eastern
Pacific ranges from the Gulf of Alaska to the Gulf of
California and the Revillagigedo Islands and from Panama
to Chile (Klimley & Ainley, 1996). Compared with other
sharks, little is known of its abundance (Compagno, 1984).
In Mexico, the white shark has been recorded at Cedros,
San Benito, Guadalupe, and the Revillagigedo Islands in the
Mexican Pacific, and is occasionally observed along the
western coast of the Baja California Peninsula (McCosker &
Lea, 1996). Heretofore, its presence in the Gulf of California
was limited to a few records (Kato, 1965; Galva
´n-Magan
˜a
et al., 1989). The aim of this study is to summarize all
records of white sharks in the Gulf of California.
MATERIALS AND METHODS
White shark captures were reported from Gulf of California
fishing camps in the States of Baja California, Baja
California Sur and Sonora, Mexico. Information on white
sharks came from three primary sources: (1) records from
local newspapers; (2) white shark sightings made by scientists
and reliable divers; and (3) shark parts or photographs exam-
ined by the authors. Whenever possible, the appropriate fish-
ermen were contacted to obtain more information about such
records. Some individuals were sexed and variously measured,
but several records lacked any reliable measurements, and
total length (TL) was estimated by examining photographs
and/or sets of jaws. To estimate TL of photographed speci-
mens, we compared the shark’s length with that of adjacent
persons or objects of known size in the photographs (Gadig
& Rosa, 1996). For calculation of TL from jaw (tooth)
measurements, we used the methodology of Shimada
(2003), measuring the height of the enamel of the largest
tooth.
RESULTS
Thirty-eight records of white shark from 17 localities in the
Gulf of California are presented here (Table 1; Figure 1).
The locality with most sightings/captures was El Golfo de
Santa Clara, Sonora, in the uppermost Gulf. In the central
Gulf, between the Baja California Peninsula and Sonora
(including several islands), a higher number of white sharks
were recorded compared to lower Gulf localities, where
records were restricted to the peninsula in the south-western
Gulf.
White shark captures occurred mainly in (now illegal)
totoaba gill-nets or shrimp trawl nets at different depths
(9–90 m). Also, reliable SCUBA divers sighted white sharks
at 30– 40 m depths near San Pedro Ma
´rtir and San Pedro
Nolasco Islands (Figure 1).
Corresponding author:
F. Galva
´n-Magan
˜a
Email: galvan.felipe@gmail.com
1
Marine Biodiversity Records, page 1 of 6. #Marine Biological Association of the United Kingdom, 2010
doi:10.1017/S1755267210000977; Vol. 3; e111; 2010 Published online

Table 1. Chronology of records of white shark in the Gulf of California (See Figure 1).
No. Date Location TL (cm) Sex Remarks Source
1 1964 Bahı
´a Kino, Sonora 500 ? Photograph Carlos Navarro, personal
communication
2 Summer 1970 San Pedro Ma
´rtir Island – ? Sighted (30 m depth) by diver M. Hoyos, personal
communication
3 1974 Bahı
´a de Guaymas, Sonora 425 ? Caught in gill-net at Rio Escondido
(in front of Islas Mellizas).
Reported weight: 1000 kg
El Imparcial∗28 January 2008
4 8 February 1981 Las A
´nimas Island 268 F Photographed/carcass rendered at El
Pardito Island. Caught at 40– 90 m
depth
Authors sampled
5 9 July 1981 Punta Arenas, BCS 246 M Juvenile. Jaw set preserved at
CICIMAR
Authors sampled
6 Winter 1986 El Golfo de Santa Clara,
Sonora
450 ? Caught in totoaba gill-net (12 inch
mesh); remains of two dolphins
(Tursiops truncatus) in stomach
Picture. Carlos Navarro,
personal communication
7 1987 Bahı
´a Miramar, Guaymas,
Sonora
350 ? Stranded alive Carlos Navarro, personal
communication
8 1988 El Golfo de Santa Clara,
Sonora
400 ? Caught in shrimp-trawler net. Jaw set
preserved. Teeth length: 30 mm
Carlos Navarro, personal
communication
9 1989 El Golfo de Santa Clara,
Sonora
300 ? Jaw set preserved. Teeth length:
20.6 mm
Carlos Navarro, personal
communication
10 April 1990 El Golfo de Santa Clara,
Sonora
350 ? Jaw set preserved. Teeth length:
24.8 mm
Carlos Navarro, personal
communication
11 9 April 1990 El Golfo de Santa Clara,
Sonora
200 ? Head Carlos Navarro, personal
communication
12 December 1990 El Burro, SE of El Golfo de
Santa Clara, Sonora
650 ? Caught in totoaba gill-net set at 9 m
depth. Photograph
Carlos Navarro, personal
communication
13 January 1991 El Golfo de Santa Clara,
Sonora
300 ? Caught in totoaba gill-net Carlos Navarro, personal
communication
14 1 January 1991 El Golfo de Santa Clara,
Sonora
300 ? Caught in totoaba gill-net. Jaw set
preserved
Carlos Navarro, personal
communication
15 26 February 1991 El Burro, south-east of El
Golfo de Santa Clara,
Sonora
200 ? Caught in totoaba gill-net set at 15 m
depth. Teeth length: 19.6 mm
Carlos Navarro, personal
communication
16 March 1991 El Burro, south-east of El
Golfo de Santa Clara,
Sonora
200 ? Caudal fin and dry rests Carlos Navarro, personal
communication
17 1 March 1991 El Golfo de Santa Clara,
Sonora
250 ? Caudal fin and skeleton rests Carlos Navarro, personal
communication
18 4 April 1991 El Burro, SE of El Golfo de
Santa Clara, Sonora
200 M Caught in totoaba gill-net set at 13 m
depth. Jaw set preserved. Teeth
length: 17 mm
Carlos Navarro. Personal
communication.
19 Summer 1995 San Pedro Nolasco Island 450 ? Sighted by SCUBA divers at 40 m
depth
M. Hoyos, personal
communication
20 1996 San Pedro Ma
´rtir Island 500 F Caught on long-line set from
fisherman. Photograph
Juan Pablo Gallo, personal
communication
21 October 1996 San Pedro Nolasco Island 300 ? Sighted at the surface Sighted by Carlos Navarro.
22 25 May 1997 San Pedro Nolasco Island 235 M Juvenile (semi-calcified claspers.
26 cm long). 145 kg body weight
Fernando Ma
´rquez, personal
communication
23 25 May 1997 Isla Pa
´jaros, Bahı
´ade
Guaymas, Sonora
330 ? 350 kg body weight. Photograph and
jaw
Fernando Ma
´rquez, personal
communication
24 October 1999 North of Isla Tiburo
´n ? ? Sighted swimming at the surface over
very deep water
F. Ma
´rquez, Instituto
Nacional de Pesca, personal
communication
25 October 1999 South of Isla Tiburo
´n ? ? Sighted feeding on floating whale
carcass
T. Pfister, Prescott College,
personal communication
26 2000 Santa Rosalı
´a, BCS 284 ? TL calculated from teeth using
method of Shimada (2003)
Jaw set preserved at
CICIMAR, La Paz, BCS.
27 April 2001 Boca del A
´lamo, BCS 346 M Caught in gill-net set 25 miles
offshore. Mature well-developed
claspers
Two photographs (M. Hoyos)
28 October 2003 San Bruno, BCS 450 – 500 ? Size estimated by authors Carlos Navarro, personal
communication
29 4 June 2004 Canal de Salsipuedes 400 ? Sighted swimming with Delphinus
capensis
Carlos Navarro, personal
communication
Continued
2felipegalva
’n-magan
~aet al.

In some captured specimens, the authors did the examin-
ation of stomach contents of some adults (300 – 400 cm TL)
which consisted of bottlenose dolphins (Tursiops truncatus),
unidentified whale remains and California sea lions
(Zalophus californianus). A juvenile specimen examined had
an empty stomach.
No seasonal particularly notable shifts in distribution (‘pre-
ferences’) were seen in the records. Nineteen records were
from the cold season (December to May) and seven records
were from the warm season (June to November) (Table 1).
The presence of juveniles (,300 cm TL) was highest
during the cold season with ten records; whereas during the
warm season only one juvenile was recorded. Adults were
more common during the cold season with nine records;
whereas in the warm season six adults were recorded.
DISCUSSION
The white sharks reported here ranged from 170 to .500 cm
TL. Working with records worldwide Compagno (2001)
reported size at maturity for males to be between 350 and
410 cm TL, and between 400 and 500 cm for females.
Unfortunately, for most of our Gulf of California records we
lack data on gender and thus could not accurately determine
reproductive stage. However, we can infer from size-ranges
that 15 records corresponded to juveniles and 14 to adults
specimens. The remaining records belonged to unmeasured
individuals.
Presence of juveniles was mostly restricted to the upper
Gulf, mainly in the relatively shallow waters off the fishing
town of El Golfo de Santa Clara (Figure 1), and this is prob-
ably associated with feeding habits. Juveniles apparently
show a dietary preference for benthic and coastal fish
(Klimley, 1984; Tricas & McCosker, 1984), and the northern
Gulf is habitat to seasonally large schools of medium to large-
sized fish, such as the endemic species Gulf corvina
(Cynoscion othonopterus) and totoaba (Totoaba macdonaldi),
which could be consumed by juveniles.
Navarro & Arizmendi (2003) and Salomo
´n-Aguilar et al.
(2009) reported an abundance of newborns and pregnant
females of several shark species in the Gulf, suggesting that
this area could be an important nursery area. Klimley
(1985) found white shark pups in California waters that
were probably born off the coast of northern Baja California
to Santa Barbara, California, at the northern edge of the tem-
perate zone.
Considering the general absence of large white sharks in
these southern coastal areas, it is possible that more
northern-occurring gravid females move southward into this
environment to release their pups so as to optimize their sur-
vival and decrease risk of predation. No newborns or pregnant
females have been recorded in the Gulf of California, and
there is no evidence of births there. However, the presence
of small (,3 m TL) juveniles, suggests that the northern
Gulf of California may be a secondary nursery ground,
where juveniles apparently migrate from cool waters in the
Pacific on the outer side of the Baja Peninsula to warmer
waters in the Gulf (http://www.topp.org/blog/2_200_mile_
journey_juvenile_white_shark) to find locations with
abundant food for growth and protection (Bass, 1978).
Juveniles were more frequent in the northern Gulf from
January to April when sea surface temperatures were lowest
(average 158C).
Adults were recorded in the Gulf of California during
the whole year at a range of sea surface temperatures
Table 1. Continued
No. Date Location TL (cm) Sex Remarks Source
30 18 July 2004 San Pedro Ma
´rtir Island 500 ? Sighted feeding on floating whale
carcass
F. Ma
´rquez, Instituto
Nacional de Pesca, personal
communication
31 26 September 2004 Santa Marı
´a (close to
Santa Rosalı
´a), BCS
500 M Three colour photographs El Sudcaliforniano∗∗,28
September 2004
32 22 December 2004 Carmen Island 600 ? Sighted at east of island, swimming
fast to dolphin (Delphinus sp.)
group
Carlos Navarro, personal
communication
33 25 December 2004 Carmen Island 400 ? Caught in shark gill-net Carlos Navarro, personal
communication
34 2004 Santa Rosalı
´a, BCS 183 ? Length calculated from jaw teeth
using method of Shimada (2003)
Jaw set preserved at
CICIMAR, La Paz, BCS
35 2 February 2006 Bahı
´a San Luis Gonzaga,
BCS
170 ? Juvenile. Photograph J. O’Sullivan, Monterey Bay
Aquarium, Personal
communication
36 17 March 2006 El Golfo de Santa Clara,
Sonora
250 ? Photograph Lloyd Findley, J.C. Barrera,
personal communications
37 July 2007 Santa Rosalı
´a, BCS ? ? Jaw set photographed D. Aurioles, CICIMAR, La
Paz, BCS, personal
communication
38 February 2010 El Golfo de Santa Clara,
Sonora
400 ? Photograph published. Weight
902 kg, caught in shrimp gill-net.
Stomach with dolphin and sea lion
remains
Tribuna de San Luis∗∗∗,21
February 2010
∗,El Imparcial, a daily newspaper published in Hermosillo, Sonora; ∗∗,El Sudcaliforniano, a daily newspaper published in La Paz, BCS; ∗∗∗,Tribuna de
San Luis, a daily newspaper published in San Luis Rı
´o Colorado, Sonora; BCS, Baja California Sur.
white shark records in gulf of california 3

(15–308C). According to Klimley (1985), water temperature
does not determine white shark distribution in adults. Bass
(1978) suggested that water temperature was not an impor-
tant factor for the presence of larger white sharks off eastern
South Africa, because they were recorded from February to
June when temperatures decreased, but they were absent
from September to January when similar temperatures
were recorded.
Fig. 1. Localities (numbered) and frequencies of records (size of circles) of white shark sightings and captures in the Gulf of California (also see Table 1).
4felipegalva
’n-magan
~aet al.

Klimley (1985) stated that adult white sharks off south-east
Farallon Island, California, were present from August to
March, but were absent from April to July. Based on records
of sightings and captures of white sharks off Farallon Island,
this last author suggested that adult white sharks travelled
southward to waters off Baja California to breed from
March to June. The presence of adults in the Gulf of
California (this paper) could support this hypothesis, although
the majority of our records represent juvenile specimens.
The presence of adult white sharks near California sea lion
(Zalophus californianus) colonies at San Pedro Ma
´rtir and San
Pedro Nolasco Islands (Aurioles & Zavala, 1994), may indicate
that prey availability influences white shark distribution in the
Gulf of California. There are records of at least 30 marine
mammal species occurring permanently or seasonally in the
Gulf of California (26 cetaceans, four pinnipeds), making it
one of the most diverse areas worldwide for marine
mammals (Vidal et al., 1993), and several of those species
could serve as important prey for adult white sharks.
Abundant availability of food, e.g. large schools of
demersal squid, small pelagic, benthic and demersal fish in
the Gulf of California would allow the presence of white
sharks, as happens with several species of both large and
small sharks which also use the shallow waters and coastal
bays of the Gulf of California as nursery areas, including ham-
merhead sharks (Sphyrna lewini and S. zygaena), smooth
hound sharks (Mustelus henlei,M. lunulatus and M. californi-
cus), blacktip sharks (Carcharhinus limbatus), Pacific sharp-
nose sharks (Rhizoprionodon longurio), and tiger sharks
(Galeocerdo cuvier) (Navarro & Arizmendi, 2003; Ma
´rquez-
Farı
´as et al., 2006; Galvan, 2009; Salomon-Aguilar et al., 2009).
Although we have little information on how the white
shark uses the Gulf of California, records of its areas of occur-
rence probably indicate feeding areas for adults around
islands, where marine mammals (especially California sea
lion) are abundant, or areas where coastal and benthic and
demersal fish are abundant and form important prey for
juveniles.
Conservation and management implications
Although the white shark is included in the Mexican Official
regulation (NOM-ECOL-059) prohibiting its commercial
capture, enforcement mechanisms are insufficient, or they
are not well implemented. There are no specific actions to
protect this shark in Mexico, even though it continues to be
captured as by-catch in artisanal fisheries off the western
coast of Baja California and in the Gulf of California.
We hope that white shark occurrences in the Gulf of
California here reported will serve to increase enforcement
of protection regulations and aid in the conservation of this
important worldwide apex predator.
ACKNOWLEDGEMENTS
We thank Juan Pablo Gallo-Reynoso and Lloyd Findley
(Centro de Investigacio
´n en Alimentacio
´n y Desarrollo,
AC-Guaymas), Rita Benavides (OVIS Organizacio
´n Vida
Silvestre AC), Omar Vidal (World Wildlife Fund-Mexico),
Jose I. Castro (National Marine Fisheries Service), John
O’Sullivan (Monterey Bay Aquarium, California), David
Aurioles (Centro Interdisciplinario de Ciencias Marinas, La
Paz), Juan Carlos Barrera (Comisio
´n de Ecologı
´ay
Desarrollo Sustentable del Estado de Sonora) and Tad
Pfister (Prescott College, Kino Bay) for information on
white shark records. We thank the Instituto Polite
´cnico
Nacional (Comisio
´n de Operacio
´n y Fomento de
Actividades Acade
´micas, Estimulo al desempen
˜o del investi-
gador y Programa institucional de formacio
´n de investiga-
dores) for research fellowships. Thanks also to two
anonymous referees for English editing and valuable com-
ments on our manuscript.
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Correspondence should be addressed to:
F. Galva
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˜a
Centro Interdisciplinario de Ciencias Marinas
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email: galvan.felipe@gmail.com
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