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

Authors:
  • Facultad de Ciencias del Mar. Universidad Autonoma de Sinaloa.

Abstract and Figures

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.
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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
(990 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 Imparcial28 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
(15308C). 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
´n-Magan
˜a
Centro Interdisciplinario de Ciencias Marinas
Apartado Postal 592
CP 23000, La Paz
Baja California Sur, Me
´xico
email: galvan.felipe@gmail.com
6felipegalva
n-magan
~aet al.
... Aunque los tiburones blancos juveniles se mueven principalmente en regiones costeras, también se han registrado en la Isla Guadalupe, donde solo hacen recorridos cerca de la costa insular (Hoyos-Padilla et al. 2016). Además, se ha documentado la presencia de tiburones de esta especie, tanto juveniles como adultos, dentro del Golfo de California (Galván-Magaña et al. 2010). En el Golfo de México se han registrado tiburones blancos juveniles y adultos, aunque su presencia en esta región es rara (Compagno 2001) y se cuenta con pocos registros (Adams et al. 1994). ...
... Debido a esta razón, los registros de pesca de esta especie son escasos, o incluso nulos si se toma en cuenta los avisos y reportes de arribo para las empresas pesqueras. Sin embargo, en los pocos estudios de las capturas incidentales de Tiburón blanco en aguas mexicanas, se puede observar que la costa occidental de Baja California es un área importante de pesca incidental de esta especie (Santana-Morales et al. 2012¸Castillo-Géniz et al. 2016, así como el Golfo de California donde se tienen datos de observaciones y de captura incidental de individuos juveniles y adultos (Galván-Magaña et al. 2010). Es complicado entender cómo es el comercio nacional de esta especie, pues solo se menciona cuando existe un estudio dirigido a documentar la captura de elasmobranquios, pero no se observa registro alguno cuando se trata de documentos referentes a su comercialización en el país. ...
... También existen flotas pesqueras industriales en Puerto Peñasco y en Guaymas, Sonora, que se dedican a la captura de tiburones de talla pequeña (conocidos localmente como cazones), escama y camarón, respectivamente. En estas pesquerías también se han documentado la captura incidental de tiburones blancos (Galván-Magaña et al. 2010). Las pesquerías en donde se ha documentado con mayor frecuencia la captura de C. carcharias son las redes agalleras, las redes de deriva y los palangres (figura 12.12). ...
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La presente obra es resultado de la participación de expertos provenientes del sector gubernamental, académico y privado, con un total de 36 autores que compilaron información contenida en investigaciones científicas y material bibliográfico (tesis de posgrado, libros y artículos científicos). Sin duda, el contenido facilitará significativamente la labor de la Autoridad Científica cites de México, pues aporta elementos para analizar y emitir DENP de manera oportuna, además de apoyar a las autoridades Administrativa y de Aplicación de la Ley de México para su efectiva implementación de la cites, cuyo tratado internacional es uno de los más efectivos para la gestión de nuestro patrimonio natural, del cual dependen la subsistencia y modos de vida en el largo plazo de las comunidades pesqueras.
... Although the movement ecology of both adult and juvenile white sharks has been widely studied in the north-east Pacific Ocean (Boustany et al. 2002;Weng et al. 2007a;Domeier and Nasby-Lucas 2008;, Nasby-Lucas et al. 2009Galván-Magaña et al. 2010;Jorgensen et al. 2012;Carlisle et al. 2012;Hoyos-Padilla et al. 2016;Bonfil and O'Brien 2015), very limited information still exists on the occurrence and distribution of the white shark on the Pacific coast of central and south America. Within the Ecuadorian Exclusive Economic Zone (EEZ), including the Galapagos Islands, a literature review has revealed that most of the available reported occurrences of white sharks in this region are from fossil records from the Pleistocene period (Altamirano-Sierra and Vargas-Nalvarte 2016; Flores-Alciva 2019). ...
... This report represents the first confirmed record of a white shark within Ecuadorian waters and one of the few available records for the Tropical Eastern Pacific outside of the coast of Mexico (Galván-Magaña et al. 2010;Becerril Garcia et al. 2019). Based on the equatorial location of the Galapagos islands, and the nearest confirmed records for this species in Mexican waters to the north and Chilean waters to the south (Fig. 2), there are two potential origins for this vagrant individual. ...
Article
The occurrence of white sharks, Carcharodon carcharias, in Ecuadorian waters has been based on informal reports and questionable circumstantial evidence. We reviewed unique video evidence from a commercial tuna purse seiner and confirmed the first record for this apex predator within Ecuadorian waters and one of the few available for the Tropical Eastern Pacific. It is hypothesized that the oceanography resulting from the 2021 La Niña ENSO event may be related to this unusual sighting. We propose a vagrant status for the Galapagos Islands until further evidence can confirm residency.
... The incidental capture of white sharks to provide specimens for research depends on the nature of regional fisheries. In some countries where coastal artisanal fisheries are intense, the chances of encountering a white shark may be higher (Galván-Magaña et al. 2010, Márquez-Farías & Lara-Mendoza 2017. In oceanic regions where longline fleets operate, the catch rates of white sharks are relatively unknown. ...
Article
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Length at life stages of the white shark Carcharodon carcharias is not well known for most of the 9 populations of this species, including in the western North Atlantic (WNA). We analyzed length and maturity data by sex for 87 white sharks with sizes ranging 138-501 cm total length (TL), captured, studied, and released by OCEARCH during 2012-2022, off the US and Canadian Atlantic coasts. A binary logistic regression was used to estimate the length-at-maturity ( L 50 ) for the WNA white shark with a Bayesian statistical framework using a Markov chain Monte Carlo method for numerical integration. Different trials using noninformative and informative priors were tested. The posterior probability distribution for L 50 , steepness of the model (φ), and 95% credible intervals (CI) of the logistic model for females were L 50 = 411.3 cm TL (CI: 390.8-432.6 cm TL) and φ = 10.5 (CI: 5.7-17.8) and for males were L 50 = 334.9 cm TL (CI: 321.2-348.2 cm TL) and φ = 7.5 (CI: 4.2-12.4). These L 50 values are somewhat smaller than previously reported sizes-at-maturity for both sexes of this species. An ordinal logistic regression allowed us to determine the probability of being in the various life stages (young-of-the-year, juvenile, and adult) at a particular size. Estimating the length at any life-history stage of white sharks along with age estimates is useful for determining the reproductive value of the population and ultimately for estimating the relative contribution (elasticity) of vital rates to population growth.
... Los registros de captura (dirigida o incidental) de C. carcharias en estudios pesqueros del Pacífico mexicano son escasos (Galván- , Cartamil et al. 2011, al igual que en el GmC (Applegate et al. 1979, Marín-Osorno 1992, Bonfil 1997, Castillo-Géniz et al. 1998, Pérez-Jiménez y Méndez-Loeza 2015. Galván-Magaña et al. (2010) analizaron los registros confiables de captura y avistamientos de C. carcharias dentro del GC entre 1964 y 2010, encontrando que de 21 registros de organismos, seis correspondieron a organismos capturados antes de 1992 con redes agalleras para capturar totoaba (Totoaba mcdonaldi), prohibidas a la fecha, dos a redes de arrastre camaroneras, tres a redes y palangres de uso no especificado y únicamente una a red específicamente destinada a la captura de tiburón, siendo para el resto desconocida la causa de muerte. La mayor captura de C. carcharias con redes y palangres tiburoneros artesanales en aguas mexicanas se ha documentado en la costa occidental de Baja California entre 2006 y 2008, siendo relativamente baja (0.14% de la captura con redes y palangres, n = 10 629) (Cartamil et al. 2011, Santana-Morales et al. 2012. ...
... Just to the south in Baja, Mexico, a nursery ground has been described in Bahia Sebastian Vizcaino (Oñate-Gonzaĺez et al., 2017). Additional nursery areas in the Gulf of California have been proposed based on the movement of large females, although captures of young-of-the-year sharks there are rare (Galvań-Magaña et al., 2011; White sharks are hypothesized to spend~three years in these nursery grounds feeding upon cephalopods, teleosts and elasmobranchs until they reach lengths of~200-250 cm. As larger juveniles and sub-adults these white sharks recruit primarily to the north of Point Conception, CA and tags along with photo ID indicates they are present in central California or to Guadalupe Island~250 km offshore of northern Mexico, with large aggregations of pinnipeds residing in both regions (Weng et al., 2007a;Oñate-Gonzaĺez et al., 2017). ...
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Marine animals often move beyond national borders and exclusive economic zones resulting in a need for trans-boundary management spanning multiple national jurisdictions. Highly migratory fish vulnerable to over-exploitation require protections at international level, as exploitation practices can be disparate between adjacent countries and marine jurisdictions. In this study we collaboratively conducted an analysis of white shark connectivity between two main aggregation regions with independent population assessment and legal protection programs; one off central California, USA and one off Guadalupe Island, Mexico. We acoustically tagged 326 sub-adult and adult white sharks in central California (n=210) and in Guadalupe Island (n=116) with acoustic transmitters between 2008-2019. Of the 326 tagged white sharks, 30 (9.20%) individuals were detected at both regions during the study period. We used a Bayesian implementation of logistic regression with a binomial distribution to estimate the effect of sex, maturity, and tag location to the response variable of probability of moving from one region to the other. While nearly one in ten individuals in our sample were detected in both regions over the study period, the annual rate of trans-regional movement was low (probability of movement = 0.015 yr⁻¹, 95% credible interval = 0.002, 0.061). Sub-adults were more likely than adults to move between regions and sharks were more likely to move from Guadalupe Island to central California, however, sex, and year were not important factors influencing movement. This first estimation of demographic-specific trans-regional movement connecting US and Mexico aggregations with high seasonal site fidelity represents an important step to future international management and assessment of the northeastern Pacific white shark population as a whole.
... The NEP white shark population spans two adult aggregation areas, Guadalupe Island (GI) and central California (CC), and two nursery grounds that are geographically distant from one another and located in Sebastian Vizcaino Bay (SVB) in Baja California (BC), Mexico, and the Southern California Bight (SCB) in the USA (Klimley 1985, Domeier 2012, Lowe et al. 2012, Santana-Morales et al. 2012, Oñate-González et al. 2017, Tamburin et al. 2019. Whereas newborn and YOY white sharks are seasonally present in nursery grounds, juvenile white sharks travel among coastal areas until they become sub-adults and recruit to adult populations (Dewar et al. 2004, Weng et al. 2007, Galván-Magaña et al. 2010, Domeier 2012, Hoyos-Padilla et al. 2016. By understanding the migratory and connectivity patterns among these areas and the genetic patterns of the population, a comprehensive picture of the ecological and evolutionary processes operating on and within the NEP white shark population may be generated. ...
Article
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The Northeastern Pacific (NEP) population of white sharks (Carcharodon carcharias) is genetically distinct from the rest of the world. This uniqueness results from adult fidelity to central California and Guadalupe Island aggregations sites. The strong mitochondrial genetic structure between the white sharks of central California and Guadalupe Island is also present, which indicates female philopatry. To date, few studies using nuclear DNA have found evidence of genetic patterns in the NEP white shark population, which could indicate that these sharks exhibit sex-biased dispersal. In this study, we evaluated the genetic structure, connectivity, and genetic diversity of NEP white sharks using samples from the southern California Bight (SCB), Baja California (including Sebastian Vizcaino Bay), the Gulf of California, and Guadalupe Island (GI) using nDNA (i.e. microsatellite loci). A total of five loci were successfully genotyped in 54 individuals. The patterns found in this study indicated low levels of genetic diversity among all localities (observed heterozygosity: Ho = 0.47), likely due to a founder effect. A slight genetic structure was present for NEP localities in this study (FST = 0.045, P = 0.0001), mainly identified between the SCB and GI locations. A sibship assignment analysis indicated low and moderate probabilities of full-and half-siblings between white shark juveniles from coastal areas, suggesting a high degree of connectivity between nursery areas in the NEP. Our results suggest that juveniles can mask the genetic structure in coastal zones.
... En México, la norma oficial "NOM-029-PESC-2006" establece la prohibición de las capturas de tiburón blanco así como su retención y comercialización (DOF, 2007), así como el establecimiento de una prohibición total para la captura de esta especie, obligando a la liberación de cualquier organismo que sea capturado de manera incidental (DOF, 2014). Sin embargo, hay reportes de captura incidental de tiburones inmaduros de esta especie en aguas de la costa oeste de Baja California (Oñate-González et al., 2017;Santana-Morales et al., 2012), así como del Golfo de California (Galván-Magaña et al., 2010). ...
Article
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Tiburón blanco, dos palabras que inmediatamente al escucharlas o leerlas llaman la atención, causan al mismo tiempo, terror y admiración, y sin importar cuál es tu pensamiento o sentimiento, es casi imposible no dar al menos una rápida mirada hacia aquello que tiene tan fascinantes palabras.
... The GC is a highly productive ecosystem that can provide White Sharks with abundant demersal and pelagic prey throughout ontogeny (Lluch-Cota et al., 2007), and possibly support a local White Shark population. However, some of their prey are targeted by local artisanal and industrial fisheries, which explains by-catch of White Sharks by local fisheries inside the GC (Galvań-Magaña et al., 2010;Madigan et al., 2021;Malpica-Cruz et al., 2021). Further, thirteen California sea lion (Zalophus californianus) colonies are found in the GC mainly in the central and northern reaches which might serve as an important food source for adult White Sharks (Masper et al., 2019;Pelayo-Gonzaĺez et al., 2021). ...
Article
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The conservation and management of highly migratory sharks relies on understanding age-related movements and nursery habitat utilization. We reconstructed the habitat use and migratory history of young White Sharks (Carcharodon carcharias), a highly protected species, by utilizing natural chemical tracers (element:Ca ratios and stable isotope analysis, SIA) in vertebral cartilage growth bands. Two nursery areas in the northeastern Pacific are known, but migration patterns of immature White Sharks within the Gulf of California (GC) and natal philopatry are poorly understood. Vertebrae from coastal Mexican artisanal fisheries off central Baja California in the Pacific (12 neonates and juveniles; 139-280 cm total length) and the GC (3 subadults; 289-355 cm TL) were analyzed to characterize (1) trophic histories from collagen δ¹³C and δ¹⁵N values, and (2) in utero patterns and post-birth environmental histories from element:Ca time-series. Mean δ¹⁵N values from vertebral edges of GC sharks, representing the most recent feeding, was +5‰ higher than in the Pacific, reflecting the intense denitrification that permeates the regional food web and supporting SIA as tracers of migration between regions. A subadult from the GC likely resided within the system throughout its life, and two subadults migrated into the GC. Most neonate and juvenile sharks caught in the Pacific had SIA that did not overlap with those of the GC, but a single subadult likely migrated to the GC. Element:Ca ratios displayed ontogenetic trends, with Li:Ca, Zn:Ca, and Ba:Ca significantly higher before the birth mark in sharks captured in the GC. Edge values were significantly higher in Zn:Ca and Ba:Ca in the GC compared to the Pacific, suggesting elemental ratios may serve as tracers of migration between regions. Subadult sharks collected from GC displayed elevated maternal Zn:Ca and Ba:Ca, suggesting mothers may have resided in the GC for an extensive period pre-birth. Some White Sharks may reside within the GC from birth until at least the subadult stage (ca. 3 m TL), and there may be an unidentified nursery. Chemical tracers, coupled with genomic and tagging studies, should improve understanding of the importance of the GC to White Shark populations in the northeast Pacific.
Chapter
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This chapter synthesizes information on national and international regulations in force (as of July 2018) for fisheries management, conservation, and sustainable use of shark and batoid biodiversity in the Mexico. The document is a comprehensive review of relevant published information complemented with information derived from specific interviews conducted by the author to a large number of actors from all sectors (industrial fishing, artisanal fishing, sport fishing, government, NGOs, and academia) between October and December 2014. The focus of the interviews was on the effectiveness of existing regulations towards guaranteeing the conservation of shark and batoid species. The overall analysis indicates that there is a wide range of fisheries management and conservation instruments both nationally and internationally, which are generally a good starting point to ensure the conservation and sustainable use of sharks and batoids in the country, but this is not enough, since there were important gaps observed especially in fisheries management. Additionally, an analysis of 40 Protected Natural Areas (PNA) in place in Mexico as of 2014 and which have or could have species of elasmobranchs inside them (Bonfil 2014) indicates that 10 of them do not have Management Programs, and that 22 out of 30 existing management programs for PNAs do not contain specific measures for the conservation of elasmobranchs or do not list them as existing in the PNA. The main recommendations of the analisis are: a) to reinforce and expand the programs and mechanisms of inspection, surveillance, monitoring and follow-up of all regulations for the fisheries and conservation sectors; b) to prepare as soon as possible Management Programs for all PNAs where sharks and rays are found, and modify the existing ones so that they all explicitly include the species of sharks and rays that occur in each PNA and especially, to include specific measures for the conservation of elasmobranchs in them; c) as an integral part of a strategy for change, it is recommended to implement permanent programs of environmental education focused particularly onto the actors of the fishing sector (including fishermen, processors, intermediaries, wholesalers and retailers, exporters and consumers), who are the ones who interact daily with sharks and batoids, and by this means solve the great gap in environmental awareness that exists, and d) to reassess the conservation status of manta and devil rays as well as sawfishes, with the criteria of including or updating them in NOM-059-SEMARNAT-2010.
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There are reliable records from the Gulf of California for 30 species of marine mammals representing eight families: the Phocoenidae (one species), Delphinidae (12), Ziphiidae (three), Physeteridae (three), Eschrichtiidae (one), Balaenopteridae (six), Otariidae (two), and Phocidae (two). -from Authors
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El libro es una compilacion de reportes de investigacion sobre la importancia que revisten los Recursos Marinos y los servicios ecosistemicos en el desarrollo regional
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Sharks show high biological fragility and, given the intense fishing regimes to which they are exposed in the Gulf of California, it is necessary to establish a conservation and management strategy providing for the protection of their nursery areas. We reviewed the literature concerning shark reproductive biology to determine priority management areas in the Gulf of California by complementarity analysis and different selection criteria. Four levels of management and conservation priority were determined for six quadrants: level 1 corresponded to the area off Mazatlán (Sinaloa) and the area of El Sargento, La Ventana, and Punta Arenas (Baja California Sur); level 2 to the areas of Teacapán (Sinaloa) and Seri (Sonora); level 3 to the areas of San Francisquito-El Barril (Baja California) and Kino Bay (Sonora); and level 4 to the area of La Manga (Sonora). Analysis of space-time variables in a geographic information system indicated that 71% of the commercially important shark species concentrate in coastal zones, mainly in bays, coastal lagoons, estuaries, and wetlands (central and southern Gulf of California) during spring and summer (May-August), except for Prionace glauca, Isurus oxyrinchus, Alopias pelagicus, and Squatina californica that reproduce in winter and spring. The protection of recruitment areas (critical habitats) during peak breeding periods should be an essential part of any resource management plan.
Chapter
We report on 20 confirmed and five purported but unreliable incidents of unpro-voked attacks by white sharks on humans in California and Oregon between 1993 and 2003. All attacks involved white sharks (Carcharodon carcharias). The discussion , map, and tables from McCosker and Lea's (1996) report are updated. The majority of attacks occurred at or near the surface, near shore, and often in the vicinity of pinniped colonies and/or river mouths and harbors. Attacks have now occurred during all months, and on surfers, breathhold and scuba divers, swimmers, hookah divers, kayakers, and, for the first time, on bodyboarders, a windsurfer, and a scuba diver using an electric propulsion device. Typical attack scenarios suggest that an adult C. carcharias mistakes its victim for a pinniped, its normal prey. Shark attacks were fewer during the extreme 1997–1998 ENSO (El Niño/Southern Oscillation) oceanographic warming event. The defensive activity of humans after being attacked and its effect are discussed. We also comment on recent legislation concerning white shark protection and disallowing the attraction of white sharks by chumming. In 1996, we (McCosker and Lea, 1996) reviewed the history, human activity, and shark activity involved with unprovoked attacks by white sharks (Carcharodon carcharias) upon humans in the eastern North Pacific Ocean (ENP). The last attack that we reported upon was that involving Rosemary Johnson on 10 October 1993. We begin this study with an attack that occurred so late in 1993 that we were unable to include it in our earlier paper. In the subsequent decade 20 unprovoked attacks upon humans by white sharks have occurred in the ENP. We herein report upon those attacks and update our analysis and conclusions. The following is a brief review of literature concerning attacks by white sharks in the ENP.
Article
Carcharodon carcharias was studied at Dangerous Reef, South Australia. A single bit action is composed of a uniform sequence of jaw and head movements. Various approach behaviors to baits were documented. Small sharks (<3 m) feed primarily on fish prey, while larger sharks feed on marine mammals, especially pinnipeds. Telemetric studies of white shark thermal biology show that they are warm-bodied, c4-5oC above ambient water temperature. -from Sport Fishery Abstracts