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Transoceanic Migration, Spatial Dynamics, and Population Linkages of White Sharks

  • El Colegio de la Frontera Sur – Unidad Chetumal

Abstract and Figures

The large-scale spatial dynamics and population structure of marine top predators are poorly known. We present electronic tag and photographic identification data showing a complex suite of behavioral patterns in white sharks. These include coastal return migrations and the fastest known transoceanic return migration among swimming fauna, which provide direct evidence of a link between widely separated populations in South Africa and Australia. Transoceanic return migration involved a return to the original capture location, dives to depths of 980 meters, and the tolerance of water temperatures as low as 3.4 degrees C. These findings contradict previous ideas that female white sharks do not make transoceanic migrations, and they suggest natal homing behavior.
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subtracting each judge’s rating of the typical
American from his or her rating of the typical
compatriot for each NCS item. Assuming that
cultures agree on the typical American, this proce-
dure in effect subtracts the bias plus a constant and
leaves a potentially better estimate of national
character. We standardized the differences as T
scores, using difference score normative values from
the worldwide sample, excluding the United States.
The difference scores were highly correlated with
NCS scores (rs 0 0.65 to 0.91, P G 0.001) and
provided essentially the same results. ICCs between
difference scores and NEO-PI-R observer ratings
ranged from –0.44 for England to 0.48 for Lebanon
(median, 0.03). ICCs between differences scores and
NEO-PI-R self-reports ranged from –0.47 for Russia
to 0.53 for Poland (median, 0.01). For the five
factors, correlati ons with observer ratings across
cultures ranged from 0.08 to 0.23, and those with
self-reports ranged from –0.37 to 0.23. These results
suggest that the lack of correspondence between
NEO-PI-R and NCS profiles is not simply due to
different sta ndards of evalua tion in different
cultures. A different issue concerns the reference-
group effect (28), according to which self-reports
and observer ratings of individuals are implicitly
made by reference to the distribution of scores in the
rater’s culture. Such an effect would tend to make
aggregate personality scores uniform for all cultures,
and the failure to find correlations with NCS factors
would be due to a lack of variation in aggregate
NEO-PI-R means. However, NEO-PI-R means in fact
vary systematically across cultures and show strong
correlations across methods and with other culture-
level variables (12, 14). Thus, the reference-group
effect cannot explain the failure to find correlations
with NCS scales.
28. S. J. Heine, D. R. Lehman, K. P. Peng, J. Greenholtz,
J. Pers. Soc. Psychol. 82, 903 (2002).
29. F. van de Vijver, K. Leung, J. Pers. 69, 1007 (2001).
30. D. L. Hamilton, T. L. Rose, J. Pers. Soc. Psychol. 39,
832 (1980).
31. T. W. Adorno, E. Frenkel-Brunswik, D. J. Levinson, R. N.
Sanford, The Authoritarian Personality [Norton, New
York, 1969 (original work published 1950)].
32. F. H. Allport, The Nature of Prejudice (Houghton
Mifflin, New York, 1954).
33. R.R.M. receive s royalties from the Revised NEO
Personality Inventory. This research was supported
in part by the Intramural Research Program of NIH,
National Institute on Aging. Czech participation was
supported by grant 406/01/1507 from the Grant
Agency of the Czech Republic and is related to
research plan AV AV0Z0250504 of the Institute of
Psychology, Academy of Sciences of the Czech
Republic. S.G.’s participation was supported by the
Turkish Academy of Sciences. Burkinabe
and French
Swiss participation was supported by a grant from
the Swiss National Science Foundation to J.R. The
data collection in Hong Kong was supported by
Research Grants Council Direct Allocation Grants
(DAG02/03.HSS14 and DAG03/04.HSS14) awarded
to M.Y. Data collection in Malaysia was supported by
Univesiti Kebangsaan Malaysia Fundamental Re-
search Grant 11JD/015/2003 awarded to K.A.M.
Portions of these data were presented at the 113th
Convention of the American Psychological Association,
August 2005, Washington, DC. For helpful comments
on the manuscript, we thank Y. H. Poortinga; for their
assistance on this project we t hank F. Abal, L. de
Almeida, S. Baumann, H. Biggs, D. Bion, A. Butkovic
C. Y. Carrasquillo, H. W. Carvalho, S. Catty, C.-S.
Gonzalez, A. Gramberg, H. Harrow, H . Imuta, R.
Ismai l, R. Kamis, S. Ka nnan, N. Messoulam, F. Molina,
M. Montarroyos Calegaro, S. Mosquera, J. C. Munene,
V. Najzrova, C. Nathanson, D. Padilla, C. N. Scollon, S. B.
Sigurdardottir, A. da Silva Bez, M. Takayama, T. W.
Teasdale, L. N. Van Heugten, F. Vera, and J. Villamil.
Supporting Online Material
Materials and Methods
Tables S1 and S2
Appendix S1
11 July 2005; accepted 31 August 2005
Transoceanic Migration, Spatial
Dynamics, and Population
Linkages of White Sharks
n Bonfil,
Michael Mey
Michael C. Scholl,
Ryan Johnson,
Shannon O’Brien,
Herman Oosthuizen,
Stephan Swanson,
Deon Kotze,
Michael Paterson
The large-scale spatial dynamics and population structure of marine top
predators are poorly known. We present electronic tag and photographic
identification data showing a complex suite of behavioral patterns in white
sharks. These inclu de coastal return migrations and the fastest known
transoceanic return migration among swimming fauna, which provide direct
evidence of a link between widely separated populations in South Africa and
Australia. Transoceanic return migration involved a return to the original capture
location, dives to depths of 980 meters, and the tolerance of water temperatures
as low as 3.4-C. These findings contradict previous ideas that female white sharks
do not make transoceanic migrations, and they suggest natal homing behavior.
Great white sharks (Carcharodon carcharias)
occupy the apex of most marine food webs in
which they occur. Their major centers of abun-
dance are in the coastal waters of California–
Baja California, Australia–New Zealand, South
Africa, and, formerly, the Mediterranean Sea
(1–3). Management and conservation of this
threatened species (4, 5) have been limited,
partly because its space utilization and mi-
grations and the linkages between popula-
tions were poorly understood and difficult to
research until the development of sophisticated
telemetry instruments and high-resolution ge-
netic markers for the species (6–9). Long be-
lieved to primarily be shelf inhabitants, white
sharks are now known to be more pelagic and
to travel from California to Hawaii (6). Males
are assumed to move between distant popula-
tions, whereas females have been assumed to
be nonroving and philopatric (9).
We tagged white sharks off the Western
Cape of South Africa between June 2002 and
November 2003 with pop-up archival satellite-
transmitting (PAT) tags (n 0 25), near-real-time
satellite tags (from here onward, Bsatellite
tags[)(n 0 7), and acoustic tags (n 0 25) in
order to study their spatial dynamics (table S1).
Using high-resolution photographic identifica-
tion techniques, we have recorded the daily
presence or absence of individual white sharks
off Gansbaai (34-39S, 019-24E; Western
Cape) since October 1997 (10).
Electronic tagging and photographic identi-
fication records reveal complex spatial dynam-
ics in white sharks, which we categorized into
four behavioral patterns: rapid transoceanic re-
turn migrations, frequent long-distance coastal
return migrations, smaller-scale patrolling, and
site fidelity. A white shark performed a previ-
ously unknown fast transoceanic return migration
spanning the entire Indian Ocean, swimming
coast-to-coast from South Africa to Australia
and back. This È380-cm total length (TL;
measured as a straight line from the tip of the
snout to the end of the upper caudal lobe)
female shark (number P12), PAT-tagged on 7
November 2003 off Gansbaai, traveled in 99
days to a location 2 km from shore and 37 km
south of the Exmouth Gulf in Western Aus-
tralia (22-0105µS, 113-5313µE; Fig. 1A).
This shark_scourseofÈ11,100 km (11)en-
tailed a counterclockwise displacement of more
than 750 km off the southern tip of Africa,
followed by a remarkably direct path toward
northwestern Australia, indicating that white
sharks do not need oceanic islands as gate-
ways for transocea nic migrations, as previ-
ously hypothesized (12). Shark P12 traveled
at a minimum speed of 4.7 km hour
its migration to Australia (13), which is the
fastest sustained long-distance speed known
among sharks (14 –17 ) and comparable to
Wildlife Conservation Society, 2300 Southern Boulevard,
Bronx, NY, 10460, USA.
Marine and Coastal Manage-
ment Branch, Department of Environmental Affairs and
Tourism, Private Bag X2, Roggebaai 8012, Cape Town,
Western Cape, South Africa.
White Shark Trust, Post Of-
fice Box 1258, Strand Street 6, Gansbaai 7220, Western
Cape, South Africa; and Department of Zoology, Univer-
sity of Cape Town, Rondebosch 7700, Western Cape,
South Africa.
Department of Zoology and Entomology,
University of Pretoria, Pretoria 0002, South Africa.
*To whom corresponde nce should be ad dressed.
.Present address: Sea Technology Services, Ground
Floor, Foretrust House, Martin Hammerschlag Way,
Cape Town, Western Cape, South Africa.
th at of some of the fastest-swimming tunas
(18, 19). Records obtained through photo-
graphic identification revealed the return of
P12 from Australia back to its original tagging
site on 20 August 2004 (Fig. 2 and fig. S1),
evidencing site fidelity and an outstanding
navigational ability. Shark P12 performed the
fastest transoceanic return migration recorded
among marine fauna (14, 20), taking just
under 9 months to complete a circuit of more
than 20,000 km. Logged records from the
photographic identification study show that
P12 is a seasonal visitor (from June to De-
cember) to the Gansbaai area (table S2). It
has been recorded during 38 different days
spanning 1999–2004, suggesting that it is a
South African shark and that its transoceanic
return migration could be common. A second
PAT-tagged shark (unsexed, È200- to 230-cm
TL; number P3) traveled to an offshore lo-
cation 242 km SE of Port Elizabeth, where its
tag detached on 26 December 2003, in what
might have been the first leg of a migration
toward Australia (Fig. 1A).
Fig. 1. Transoceanic
migration of a white
shark from South Af-
rica to northwestern
Australia and possible
first leg of a second
shark. (A) Positions of
(dots) and track fol-
lowed by (black line)
shark P12 during coast-
al and transoceanic
movement; geolocation-
estimated positions
were corrected using
SST data to derive
positions shown (11).
The first leg of another
possible transoceanic
migration to Australia
(or an offshore move-
ment toward the north-
east coast of South
Africa) is shown by the
pop-up location of the
PAT tag from shark P3
(blue line and square).
Tagging and pop-up
for P12, 7 November
2003 and 28 February
2004; for P3, 14 April
2003 and 25 December
2003. SST is an average
composite at 4 km
resol utio n for daily
Moderate Resolution
Imaging Spectro-
radiometer data
from 23 November
2004. Southwest In-
dian Ridge shown as
white depth contours
(100 to 2000 m). The
scale bar represents
5000 km; the white
arrow marks the tag
deployment location.
(B) Differential time-
at-depth patterns dur-
ing the coastal and
oceanic legs of shark
P12’s trip, showing a
bimodal pattern with a
strong preference for
the depths of 0.0 to
0.5 m and 500 to 750 m
during transoceanic
travel. (C) Minimum
(black line and squares)
and maximum (bright
blue line) depths and
minimum temperature
(orange dots) visited during the coastal and oceanic phases of movement; all data are in 6-hour periods.
Transoceanic return migration is previously
unknown in white sharks and only suspected in
other chondrichthyans. Our results provide
direct evidence of a physical link between
two of the most important and widely sepa-
rated white shark populations, and they con-
firm philopatry in white sharks. They also
prove that female white sharks are capable of
transoceanic migrations and indicate that the
sex-biased dispersal of this species (9) is not
necessarily based on differences in the pro-
clivity of either sex to undertake transoceanic
migrations, but is probably attributable to
differences in how these migrants become
reproductively integrated into the Brecipient[
population. In light of our data, the transmis-
sion of nuclear, and not mitochondrial, genetic
material between South Africa and Australia
(9) could be explained if (i) both sexes make
transoceanic migrations, but only males repro-
duce in the recipient population, and/or (ii)
females make transoceanic migrations and
mate with males from the recipient popula-
tion, only to return to their original location to
give birth. Indeed, the migration of P12 from
South Africa to Australia corresponds to what
is thought to be the mating season in this re-
gion (21). An eventual return of this shark to
give birth in South Africa would prove natal
homing in white sharks, as has been sug-
gested for other shark species (22, 23), and
would support recent theories about the simi-
larity of reproductive strategies among a wide
range of marine taxa (24).
The mechanisms used by P12 to navigate to
Australia and back remain unknown; aside
from a few shallow seamounts on the South-
west Indian and Ninety East Ridges, there are
no other topographic features that could be
used for orientation on the route it followed
(Fig. 1A). We analyzed the satellite-transmitted
summary data to reveal the diving pattern of
P12 and found that during eastward trans-
oceanic migration, it made frequent deep dives,
reaching record maximum depths (980 m) (25),
experienced record ambient temperatures of
3.4-C, and spent 18% of the time at depths
of 500 to 750 m (Fig. 1, B and C). This shark
spent considerably more time (61%) just be-
low the surface (0.0 to 0.5 m) while in oceanic
waters than when in coastal waters (23%),
swimming most of the time (66%) above 5 m
during this trip. A strong preference for sur-
face swimming during oceanic travel is a be-
havioral pattern previously unreported in white
sharks (1, 2, 6, 26 ). We speculate that, like
many other vertebrates (14), white sharks could
be using visual stimuli such as celestial cues
as an important navigational mechanism in
addition to, or instead of, following gradients
in Earth_smagneticfieldasiscommonlyac-
cepted behavior for sharks (27).
Great white sharks undertake long-distance
return migrations along the South African coast
with relative frequency, as revealed by the track-
ing of satellite tags and by PAT tag pop-up
locations (Fig. 3 and fig. S2). They travel from
high-abundance sites in the Western Cape
(28, 29) to waters as far as 92000 km away off
kwaZulu-Natal and beyond, using underwater
routes along the continental shelf, then return
to their original tagging sites off the Western
Cape after 4 to 6 months. A 284-cm TL female
(S1) was fitted with a satellite tag in Mossel
Bay (34-08S, 22-07E) on 24 May 2003 and
completed the first tracked long-distance return
migration for a chondrichthyan, moving in
65 days to waters northeast of Delagoa Bay
(Mozambique) and outside the South African
Economic Exclusive Zone, where white sharks
are legally protected (Fig. 3). S1 returned to
Mossel Bay 162 days after being tagged, and
was photographed with its transmitter still at-
tached. Shark S2, a 310-cm TL female double-
tagged with satellite and acoustic tags in Mossel
Bay on 31 May 2003, was tracked for 46
days to the Tugela Bank, then recorded by our
acoustic-tag bottom monitors back in Mossel
Bay 123 days after being tagged (Fig. 3). In
total, 25% of tagged sharks that yielded in-
formation moved from the Western Cape to
kwaZulu-Natal and beyond, and 12.5% showed
return migrations (Fig. 3 and fig. S2). The high
proportion of immature white sharks (table S1,
Fig. 3, and fig. S2) moving to the rich en-
vironment of the Tugela Bank (30, 31) suggests
that these long-distance coastal return migra-
tions might be feeding-related events.
Records obtained from satellite and PAT tags
reflect additional spatial dynamics patterns in
white sharks, including smaller-scale patrolling
behavior and site fidelity (Fig. 3 and figs. S3 and
S4). These patterns and the return migrations
described above suggest a wider and more com-
plex range of behavioral patterns in white sharks
than was previously thought to exist. The dis-
covery of a trans–Indian Ocean return-migrating
white shark after a relatively low tagging effort,
in addition to its periodic absence from Gansbaai
as evidenced through photographic records, im-
plies that the Australian and South African pop-
Fig. 2. Photogr aphic identi fi-
cation records of shark P12 at
tagging (7 November 2003) and
upon return to the tagging loca-
tion at Gansbaai (20 A ugust
2004) after its transoceanic mi-
gration to Western Australia. (A)
Trailing edge of the first dorsal
fin, showing a unique notch
pattern allowing identification;
the white lines connect corre-
sponding notches in both photo-
graphs. (B) Right side of the first
dorsal fin, with magnified details
(left insets) showing a unique
black pigmentation pattern aid-
ing identification.
ulations maintain a physical link within a single
generation and that this return migration might
be more common than is presently known.
Our studies show that we do not have a full
understanding of the ways in which identified
populations are connected. The movement of a
female to a region of Australia known for the
presence of Australian white sharks and its
return to South Africa, in conjunction with pre-
vious genetic studies, implies that earlier hypothe-
ses about sex-biased dispersal might need to be
modified. Males are currently considered to be
the ones who move between populations (9), but
our data suggest that the connectivity between
populations could be facilitat ed also or exclu-
sively by females. The return of females mating
in Australia to give birth in South Africa would
be consistent with genetic analyses; the finding
of a rare male of South African Borigin[ in
Australia (9) might reflect equally rare birthing
in Australia by South African females.
The discoveries presented here and our lack
of evidence of sex- or size-related patterns of
space utilization in white sharks underscore the
need for additional research. Multidisciplinary
studies integrating population genetic analyses
and electronic tagging, as well as the devel-
opment of improved monitoring instruments,
should be encouraged.
Long-distance and transoceanic migrations
expose great whites to increased risk of mor-
tality as they leave domestically protected
waters in South Africa/Australia and travel into
neighboring or remote countries, sometimes
located across entire ocean basins. An in-
creasing global demand for shark products
(32), coupled with our findings, suggests that
global protective measures, such as the recent
listing of the white shark in CITES Appendix
2 (CITES, Convention on International Trade
in Endangered Species of Wild Fauna and
Flora), are warranted to ensure the effective-
ness of local protective legislation currently in
place in a handful of countries.
References and Notes
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FAO Species Catalogue for Fishery Purposes No. 1 (Food
and Agriculture Organization of the United Nations,
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10. Materials and methods are available as supporting
material on Science Online.
11. The positions estimated from archived light-level data
using geolocation algorithms provided by the manu-
facturer of the tags were corrected using satellite sea
surface temperature (SST) data with the method
described in the supporting online material.
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Elst, S. P. Wintner, S. Afr. J. Sci. 96, 365 (2000).
13. The widely accepted definition of migration is ‘the
act of moving from one spatial unit to another’ (14).
This definition is general enough to be applicable to
all animal taxa, independently of spatiotemporal
scales, and includes at its core individual migration.
14. R. R. Baker, Migration: Paths Through Time and Space
(Hodder and Stoughton, London, 1982).
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33. We thank the Natal Sharks Board and particularly S.
Dudley, G. Cliff, K. Cox, and W. Harrison for valuable
fieldwork assistance and helpful discussions in the
satellite tag study and S. Dudley for assistance in the
design and supervision of the acoustic tag study;
B. Mangold, C. Masterton, S. Parsons, P. Koen, D.
Woodborne, and P. Fre
on for the health maintenance
of sharks; R. and J. Portway, L. Staverees, D. Reynolds, T.
Keswick, and M. Rutzen for support and assistance with
fieldwork; L. Drapeau for Geographic Information Sys-
tems assistance; Smit Marine for maintaining bottom
receivers; M. N. Bester for supervision and D. Sadie for
conception of the acoustic tag study; and the Roe Foun-
dation, Wildlife Conservation Society, the South African
Government, International Fund for Animal Welfare,
World Wide Fund for Nature, and Professional Associ-
ation of Diving Instructors–Aware for financial support.
Supporting Online Material
Materials and Methods
SOM Text
Figs. S1 to Fig. S4
Tables S1 and S2
16 May 2005; accepted 21 July 2005
Fig. 3. Northeastward long-distance return migrations of South African white sharks. The figure
shows the tracks of two satellite-tagged sharks showing long-distance return migrations and
crossing to Mozambique. Shark S1 (black trace) left Mossel Bay after tagging (24 May 2004); moved
rapidly to Bird Island, residing within a limited area (385 km
) for 27 days; and continued northeast
along the shelf edge, then in oceanic waters beyond the Agulhas Current, reaching Mozambique 65
days after tagging. Transmissions ceased 11 days later, to resume on Bird Island 62 days later, then
at the original tagging location on 2 November 2003. Shark S2 (white trace), tagged on 31 May 2003
with satellite and acoustic tags, traveled steadily along the coast to the Tugela Bank in 37 days,
where it ceased transmitting 9 days later and was recorded by acoustic bottom receivers back in
Mossel Bay on 1 October 2004. The red star indicates the tagging location; the dashed line indicates
projected movement during long periods without transmissions.
... Fish, including elasmobranchs, also detect subtle variations in magnetic field components (i.e. polarity, inclination angle, and total intensity), which are assumed to assist large-scale and homeward orientation (Kalmijn, 1978;Bonfil et al., 2005;Weng et al., 2007). For example, the European eel (Anguilla anguilla), displayed orientation shifts in response to very subtle variations in the ambient field (e.g. a 2.4 µT intensity increase and a 2° inclination decrease) (Naisbett-Jones et al., 2017). ...
Ces dernières années, la volonté d’exploiter les énergies marines renouvelables s’est renforcée et les projets de construction en haute mer se multiplient. L’électricité ainsi produite est acheminée jusqu’à la côte par un réseau de câbles sous-marins généralement enfouis dans le sédiment. Or, ces derniers émettent des champs magnétiques alternatifs AC ou continus DC d’intensité élevée (jusqu’à 30 fois supérieure au champ géomagnétique), dont les effets potentiels sur la faune marine sont encore mal connus. De nombreux organismes marins utilisent en effet le champ magnétique terrestre pour orienter leur déplacement à petite et large-échelle. Dans ce contexte, cette thèse avait pour objectif d’explorer les réponses comportementales d’organismes benthiques, lors d’exposition à des champs magnétiques d’intensités similaires à celles théoriquement émises par les câbles sous-marins. Selon une approche multi-modèles ciblant des groupes taxonomiques variés, les expérimentations ont été menées en milieu contrôlé, sur la raie bouclée Raja clavata, l’étrille Necora puber, la moule bleue Mytilus edulis et le couteau arqué Ensis magnus. Les champs magnétiques artificiels ont été émis grâce à un dispositif, surnommé le Magnotron, basé sur le principe des bobines de Helmholtz et couplé à une interface numérique permettant le contrôle des intensités générées. Des comportements à forte valeur écologique ont été étudiés : chez la raie le comportement de camouflage, chez l’étrille les comportements de mise à l’abri, d’alimentation et de déplacements et chez la moule et le couteau, les activités de filtration et de bioturbation, respectivement. De manière générale, les expositions aux champs magnétiques artificiels n’ont pas causé de changements comportementaux significatifs chez aucune des quatre espèces. Ces travaux de thèse sont les premiers à évaluer la magnéto-sensibilité des mollusques bivalves et fournissent des données précieuses pour de futures recherches. Il est maintenant nécessaire d’évaluer les effets d’expositions de moyenne et longue-durée et d’explorer la sensibilité des jeunes stades de vie.
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Climate change influences marine environmental conditions and is projected to increase future environmental variability. In the North Atlantic, such changes will affect the behavior and spatiotemporal distributions of large pelagic fish species (i.e., tunas, billfishes, and sharks). Generally, studies on these species have focused on specific climate-induced changes in abiotic factors separately (e.g., water temperature) and on the projection of shifts in species abundance and distribution based on these changes. In this review, we consider the latest research on spatiotemporal effects of climate-induced environmental changes to HMS' life history, ecology, physiology, distribution, and habitat selection, and describe how the complex interplay between climate-induced changes in biotic and abiotic factors, including fishing, drives changes in species productivity and distribution in the Northwest Atlantic. This information is used to provide a baseline for investigating implications for management of pelagic longline fisheries and to identify knowledge gaps in this region. Warmer, less oxygenated waters may result in higher post-release mortality in bycatch species. Changes in climate variability will likely continue to alter the dynamics of oceanographic processes regulating species behavior and distribution, as well as fishery dynamics, creating challenges for fishery management. Stock assessments need to account for climate-induced changes in species abundance through the integration of species-specific responses to climate variability. Climate-induced changes will likely result in misalignment between Frontiers in Marine Science
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The reef manta ray, Mobula alfredi (Krefft, 1868), is a highly mobile and plankton-feeding species, classified vulnerable to extinction on the IUCN Red List for Threatened Species. Knowledge on their spatial ecology and the extent of their dispersal remain incomplete, especially within island-fragmented habitats as found in New Caledonia. Satellite telemetry was used to investigate the horizontal movement ecology of reef manta rays in New Caledonia. A total of 21 reef manta rays were tagged with pop-up satellite archival transmitting tags (21 Fastloc and 2 MiniPAT) that remained deployed for a duration ranging from 3 to 180 days (mean ± SE = 76.7 ± 50.3). Rays presented a strong site fidelity and an important affinity for coastal waters. Long-distance migrations (>300 km) were also observed, mainly through coastal and shallow water paths. Horizontal movements were compared to a home range area and classified into four distinct patterns: Fidelity, Excursion, Fidelity + Relocation and Relocation. The most dominant pattern was Fidelity, where manta rays remained within their home range for the whole duration of the tag deployment. Our findings may assist in the design of more appropriate management strategies for the species in New Caledonia and other regions worldwide. Key Contribution: This paper presents unique information on the horizontal movement ecology of reef manta rays (Mobula alfredi) in a context of an archipelago that combines continuous coastlines and islands separated by deep waters. The main results show a consistent use of shallow coastal waters for dispersal and that deep water might be a restraining factor but not a complete barrier to connectivity.
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Tonic immobility remains one of the least understood behaviors in nature. Despite this, the behavior has been described in a diversity of species across the animal kingdom. Tonic immobility has been observed in sharks and rays both in the laboratory and field. However, actual scientific studies of tonic immobility have been completed on only a few species of elasmobranchs. The behavior is frequently induced by handling an animal in a certain way rather than utilizing chemical anesthesia in order to assess body condition and implant electronic tracking devices. This behavior functions as (1) an innate defensive passive response against a predatory attack, (2) a component of courtship and copulation, and (3) a protective mechanism limiting the effect of overwhelming sensory stimulation. We present a review of the behavioral, physiological, and neurological processes that result in tonic immobility in sharks, and compare this information to the processes of tonic immobility that are better understood in mammals.
The quintessential example of evolutionary convergence is that between the shark, ichthyosaur, and dolphin. Although not closely related, the three exemplar taxa have independently evolved adaptations in morphology, physiology, and behavior that result in concomitant levels of performance that meet the requirements associated with operating in a dense, viscous, and thermally conductive marine environment. These apex marine predators display a remarkable amount of homoplasy. All three taxa have developed streamlined fusiform bodies to reduce drag when swimming. The position, type, and morphology of the control surfaces (i.e., fins, flippers, flukes) are similar for the convergent taxa. The control surfaces have different internal support structures, but function similarly to generate lift forces for stability and maneuverability. The main departure in control surface design among the three taxa is that dolphins lack pelvic fins. For dolphins, the loss of pelvic appendages is directly related to the possession of horizontally oriented caudal flukes, which perform double duty as a propulsive device and posterior stabilizer for trim control. The flukes of dolphins and caudal fins of ichthyosaurs and sharks have a lunate shape that function as an oscillating wing to generate high efficiency, lift-based thrust for high-speed swimming. The three convergent taxa are homeothermic, with a body temperature above that of the water in which they live. The advantages of an elevated body temperature are the attainment of higher maximum swimming speeds, longer and faster sustained swimming speeds, improved digestion, brain heating, and enhanced visual acuity. The convergence of the shark, ichthyosaur, and dolphin with respect to morphology, physiology, and locomotor performance reflects similar selective pressures imposed by the physical fluid environment that have dictated the independent evolutionary trajectories of these high-performance marine predators.
Achieving long-term retention of pop-up satellite archival tags (PSATs) has proven difficult for all fishes but is particularly challenging for small migrant species due to the relatively large size of tags. In this study we tested the latest and smallest PSAT model on the market, the mark-report satellite tag (mrPAT), and developed a simple, cost-effective method of tag attachment on sheepshead Archosargus probatocephalus (Walbaum 1792), a small marine fish. During laboratory trials, our method of tag attachment outperformed existing methods with two ~40 cm fish retaining their tags for three months (the duration of the laboratory study). During field deployments, data were successfully obtained for 17 of the 25 tagged fish (37-50 cm fork length). Of these, 14 tags (82%) remained on the fish until the pre-programmed release date resulting in tag retention times of up to 172 days (mean: 140 days). Our investigation represents the first extensive study into the feasibility of PSATs for monitoring fishes in this size range. We demonstrate that our method of attachment, and this latest PSAT model, are feasible for ~5-month deployments on fishes that are relatively small (~45 cm fork length). These results with A. probatocephalus represent a potentially significant advance in PSAT methodology for fishes of this size. Future investigations are needed to determine if this method is transferrable to other species in the same size range.
Addressing important questions in animal ecology, physiology, and environmental science often requires in situ information from wild animals. This difficulty is being overcome by biologging and biotelemetry, or the use of miniaturized animal-borne sensors. Although early studies recorded only simple parameters of animal movement, advanced devices and analytical methods can now provide rich information on individual and group behavior, internal states, and the surrounding environment of free-ranging animals, especially those in marine systems. We summarize the history of technologies used to track marine animals. We then identify seven major research categories of marine biologging and biotelemetry and explain significant achievements, as well as future opportunities. Big data approaches via international collaborations will be key to tackling global environmental issues (e.g., climate change impacts), and curiosity about the secret lives of marine animals will also remain a major driver of biologging and biotelemetry studies.
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In the present work, key aspects of the biology and ecology of the shortfin mako were studied. Feeding habits, analysed in two ocean basins, indicated that pelagic fish and cephalopods were the main prey items. In the South Pacific Ocean, a marked sexual segregation was found, with females being more common in the SE region; this was also the area with a higher abundance of juveniles and of late-stage pregnant females. In the North Atlantic Ocean, large-scale horizontal movements (including trans-Atlantic migrations) were identified and diel vertical behaviour patterns described. Importantly, individuals that performed wider movements away from the tagging location were less at risk from surface longline fishing. Using tagging and recapture data that spanned a ten-year period, survival, dispersal, and fishing mortality rates for both mako and blue sharks were estimated. The presence of plastics and hooks was also observed for both species, in two studied ocean basins. Finally, bycatch rates for other internationally protected shark species that are commonly caught using surface longlines was estimated based on direct observations, which were several times higher than the official reported data. The results presented here are especially relevant for improving the management measures focused on pelagic sharks.
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Modern sharks have an evolutionary history of at least 250 million years and are known to play key roles in marine systems, from controlling prey populations, to connecting habitats across oceans. These ecological roles can be quantified based on their functional traits, which are typically morphological (e.g., body size) or behavioural (e.g., feeding and diet). However, our understanding of such roles of extinct sharks is limited by the inherent incompleteness of their fossil record, which consists mainly of isolated teeth. As such, establishing links between tooth morphology and ecological traits in living sharks could provide a useful framework to infer sharks’ ecology from the fossil record. Here, based on extant sharks from which morphological and behavioural characteristics are known, we assess the extent to which isolated teeth can serve as proxies for functional traits. To do so, we first review the scientific literature on extant species to evaluate the use of shark dental characters as proxies for ecology to then perform validation analyses based on an independent dataset collected from museum collections. Our results reveal that 12 dental characters have been used in the shark literature as proxies for three functional traits: body size, prey preference and feeding mechanism. From all dental characters identified, tooth size and cutting edge are the most widely used. Validation analyses suggest that seven dental characters – crown height, crown width, cutting edge, lateral cusplets, curvature, longitudinal outline and cross‐section outline – are the best proxies for the three functional traits. Specifically, tooth size (crown height and width) was found to be a reliable proxy of all three traits; the presence of serrations on the cutting edge was one of the best proxies for prey preference; and tooth shape (longitudinal outline) and the presence of lateral cusplets were among the best indicators of feeding mechanism. Taken together, our results suggest that in the absence of directly measurable traits in the fossil record, these seven dental characters (and different combinations of them) can be used to quantify the ecological roles of extinct sharks. This information has the potential of providing key insights into how shark functional diversity has changed through time, including their ecological responses to extinction events. This article is protected by copyright. All rights reserved.
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Purpose: Among 29 different species of sharks reported in the Adriatic, the great white shark and the basking shark are included as very rare species. These two species, like other sharks, have life history characteristics, such as slow growth, delayed ages at maturity, low fecundity and long gestation periods, that make them particularly vulnerable to overfishing. A number of studies carried out throughout the world indicate that numbers of these two species decline. Methods: This paper gives collected data of records of these two species in the Eastern Adriatic, based on bibliographical research and collaboration with numerous persons and institutions. Conclusion: Since 19th century 61 records of the great white shark and 27 records of the basking shark have been collected in the Eastern Adriatic. According to obtained results, a proposal of their protection in the same area has been presented.
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Evidence of philopatric behavior in diverse species of sharks is accumulating through various sources of data, including studies of shark behavior, genetics and fisheries. If sharks display natural tendencies to return to a home area, birthplace or another adopted locality during portions of their life cycles, as opposed to roaming and dispersing throughout their overall ranges, the impact of fisheries removals and habitat alterations on shark populations and stocks could be profound, and the use of shark catch data to assess stocks could be complicated. We review the accumulating evidence for philopatry in sharks and discuss its implications for fisheries management and conservation of shark species.
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Tracking movements of marine animals for extended periods at sea is very expensive and labour intensive. The only method that shows promise for world-wide tracking in long-term studies is satellite tracking.The purpose of this study was to test this technique under operational conditions on basking sharks in the North Atlantic Ocean. These fish feed on plankton near the surface, and the long-term objective is to investigate the foraging and migratory movements in relation to sea surface temperature and plankton distribution patterns.A basking shark equipped with a special UHF radio transmitter was tracked for 17 days off the West Coast of Scotland using the ARGOS satellite data collection and location system. The shark surfaced during warm sunny weather and its movements were rather localised. Swimming speed was estimated as 0.106 body lengths per second between locations on successive satellite orbits. Simultaneous infrared imagery using the NOAA 7 AVHRR indicated the shark's movements relative to sea surface temperature variations.This preliminary experiment clearly demonstrates the feasibility of satellite-based monitoring of movements of marine animals using currently available operational satellite systems.
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The deployment of electronic data storage tags that are surgically implanted or satellite-linked provides marine researchers with new ways to examine the movements, environmental preferences, and physiology of pelagic vertebrates. We report the results obtained from tagging of Atlantic bluefin tuna with implantable archival and pop-up satellite archival tags. The electronic tagging data provide insights into the seasonal movements and environmental preferences of this species. Bluefin tuna dive to depths of >1000 meters and maintain a warm body temperature. Western-tagged bluefin tuna make trans-Atlantic migrations and they frequent spawning grounds in the Gulf of Mexico and eastern Mediterranean. These data are critical for the future management and conservation of bluefin tuna in the Atlantic.
Distribution records of white sharks in the tropical southwest Indian Ocean are both sparse and speculative. This paper provides the first confirmed records of white sharks from four localities in the region. A male white shark of about 5 m total length was taken by a fisheries vessel off Le Morne on the island of Mauritius in 1971. A white shark over 4 m long was caught at Matemwe Beach, Zanzibar, in 1993. A female white shark, estimated at 3.8 m, was taken in an artisanal net fishery near Antsiranana, in the Baie de Diego Suarez on the northeastern tip of Madagascar in 1994. A pregnant white shark, reported at 6.4 m, was taken in an artisanal net fishery near Malindi, Kenya, in 1996. At least seven embryos, 1.1 m long and weighing 10-20 kg, were found. White sharks in the tropical Indian Ocean may be predominantly large, possibly mature, specimens. Their occurrence in oceanic island waters may facilitate trans-oceanic movements, which has important consequences for the conservation and management of this species.
Species composition, sizes, trends in occurrence and catch rates of elasmobranchs caught by prawn trawlers on the Tugela Bank of Natal, South Africa, were examined from May 1989 to June 1992. Seven endemic species were recorded, the remainder having Indo-West Pacific or western Indian Ocean distributions. Most sharks were between 0,5 and 1 m long and most of the Myliobatiformes were 0,5 m in disc width. The small sizes of trawl-caught elasmobranchs indicates that the Tugela Bank functions as a nursery area for several species. None of the species examined exhibited diel patterns in frequency of occurrence, but Gymnura natalensis, Himantura gerrardi, Dasyatis chrysonota chrysonota, Sphyrna lewini and the rhinobatids occurred more frequently in warmer months. One species, Halaelurus lineatus, was more frequently taken during cooler months. Himantura gerrardi, Sphyrna lewini, Mustelus mosis and Rhizoprionodon acutus were recorded more frequently in shallower trawls (20–33 m) and G. natalensis and D. c. chrysonota more frequently in deeper trawls (33–45 m). Trawl-induced mortality was shown to be species specific, S. lewini having the highest mortality (98%). Based on catch rates recorded and trawl fleet effort, it is calculated that 44 600 elasmobranchs were caught by Tugela Bank trawlers from 1989 to 1992. About 57% of these were returned to the water alive. These figures are compared to catches made by recreational anglers and the Natal Sharks Board during the same period.
The tagging of sharks using conventional tags has long been recognized as a valuable means for studying various aspects of their life history, migrations and movements, and population structure. Conventional tags are defined as those that can be identified visually without the use of special detection equipment. Tagging studies specifically targeting sharks began in the late 1920's, and today numerous cooperative shark tagging programs exist worldwide. Cooperative programs depend on the joint participation of scientists and public volunteers to accomplish research objectives. Benefits and problems of these programs are discussed using the tagging methodologies, protocols, and results of the National Marine Fisheries Service Cooperative Shark Tagging Program. An additional 63 shark tagging studies and programs of all types are reviewed. Information useful for behavioral, biological, and fishery management studies can be derived from data resulting from these studies, including species and size composition, sex ratios, spatial and temporal distribution, migrations, movement patterns, rates of travel, delineation of pupping grounds, distribution of maturity intervals, indices of relative abundance, and recognition of individuals. Specific tagging experiments can be designed to provide additional data on age and growth, homing and site fidelity, dispersal rate, residence time, movement rates, tag shedding, and population parameters (e.g. size, mortality, recruitment, exploitation, interaction rates, and stock identity). Sources of bias inherent in tagging and recapture data include mortality, variation in tagging effort and fishing pressure, non-recovery and non-reporting of tags, and tag shedding. Recent advances in tagging methodologies that complement and extend conventional tagging studies will further our knowledge on shark movements and migrations, particularly in the areas of resource utilization and management, space utilization, and population dynamics.