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Great white shark
Carcharodon
carcharias (Linnaeus, 1758)
Class Chondrichthyes
Subclass
Elasmobranchii
Superorder Selachimorpha [Pleurotremata]
Order
Lamiformes
Family Lamnidae
Common names: White shark; maneater
(USA), white pointer, white death (Aus.), blue pointer, Tommy shark,
Uptail (S. Africa).
French: Grand requin blanc; requin blanc; Lamie
(Nice)
Spanish: Tiburón blanco; jaquetón blanco; Tauró blanc
(Catalunya); salroig (Majorca); Marraco (Barcelona); Sarda
(Canaries)
Italian: Squalo bianco; pescecane; mangia alice;
damiano (Naples); tunnu palamitu di funnu (Catania); pici bistinu
(Messina)
Croatia: Pas ljudozder
Portuguese:
Tubarão
German: Menschenhai
Maltese: Kelb
il-bahar; Kelb-il-bahar abjad; Silfjun; Huta
tax-xmara
Afrikaans: Witdoodshaai
Current IUCN Status Assessment: VULNERABLE globally
• Taxonomy & Early History
The
great white shark, within the monotypic genus Carcharodon, is
related to four other Mackerel sharks (Makos, Isurus spp. &
Porbeagles or Salmon sharks, Lamna spp.) in the Family
Lamnidae.
Only one white shark species recognised by taxonomists - but it was not
always known as Carcharodon carcharias, the 'Jagged-Toothed One'.
Carolus Linnaeus, in his 1758 tome Systema Naturae, named it
Squalus carcharias and thereafter the species was afforded a
variety of binomials, including Carcharias lamia, Carcharias verus,
Carcharodon smithii and Carcharodon rondeletii.
This shark was known from the Mediterranean in ancient times, most
probably being the fish referred to by Aristotle and other Greek writers
as the fearsome Lamia monster - a common-name still used for this
species both in Greece and in places along the coast of southern France
(where it is called the 'Lamie'). They were not uncommonly caught between
Sète and Nice in medieaval centuries, and specimens were of as much
interest to the writers of the time as they are today. In 1566, the
Montpellier-based naturalist Guillaume Rondelet noted the voracious
appetite of the Lamia ; a diet which, he commented, included tuna
and even the odd human - and suggested it was this animal, rather than a
whale, that was responsible for swallowing the prophet Jonah in the famous
biblical fable. It's not hard to see where Rondelet's reasoning
originated. The white shark was then - as it is now - a little-known,
rarely seen but greatly feared animal of mythical status, whose apparent
penchant for consuming humans (in a mystical sense!) was well-known
amongst the region's seafarers. It seems quite conceivable that, on some
ancient shoreline and unrecorded date, a white shark was caught and
eviscerated, leading to the rare discovery of human remains, perhaps
largely intact and fresh, in its stomach (e.g., see Conorelli &
Perrando, 1909, for a genuine example of this). Such an event would
unquetionably spark considerable public interest and quickly evolve into
local fable. Perhaps inserting the 'whale' element gave the story a more
benign feel, as befitting the religious context into which it is now
told.
Throughout much of the 18th and 19th Century, there was confusion in
the proper identity of the white shark amongst the Mediterranean
elasmobranch fauna. Its triangular, serrated teeth proved a cornerstone in
fuelling the nomenclaturial and descriptive mayhem that followed - not
least as a much more common Mediterranean species, the sandbar shark
Carcharhinus plumbeus, has teeth that may - at least when compared
solely by cursory, written description - fit adequately into the white
shark 'mould'. The thought of the essentially inoffensive sandbar shark
being unwittingly catapulted to 'maneater' status may seem amusing in
hindsight but, at the time, such fundamental errors of identification
generated many misrepresentative species accounts. The white shark was
often grouped collectively with carcharhinids on account of their rather
similar dentition. Poor illustrations of the white shark also abounded,
exasperating the problem. The simple fact was that very few scientists
describing this animal had actually seen one, either dead or alive, and
much of the topical knowledge explicating both its physical appearance and
behaviour drew more upon hearsay and mariner's lore than biological
fact.
Marcus Bloch's (1785-95) illustration of Squalus carcharias is a
typical case-in-point. The excised jaws are depicted upside-down - a
fundamental mistake later to be followed blindly by other authors - and
the shark itself bears only a limited resemblance to the fish we call
Carcharodon carcharias. With an asymmetrical tail, small gill-slits
and sail-like first dorsal fin, it might come as no surprise that the
drawing has more than a passing similarity to Carcharhinus plumbeus.
Arguably, it is only the single tooth, illustrated alongside, that can
be readily attributed to the white shark. Meanwhile, Bloch's white shark
"mugshot" doubtlessly condemned yet more benign sandbars to the maneater's
Hall of Fame. It is poignant to add that a much earlier depiction,
prepared by Guillaume Rondelet in 1554, was far more accurate than many
later images - correctly showing a crescentic caudal fin and caudal keels.
Even the relative positions of second dorsal and anal fins are
precise.
Similarly, C.L. Bonaparte (1832-1841) illustrated the white shark in
his description of Italian vertebrate fauna. His rendition is essentially
accurate and almost certainly based upon a freshly-caught specimen.
Interestingly, the black axillar blotch so often found on these sharks is
missing from the picture - and indeed is often absent on many
Mediterranean examples.
In 1838 L. Agassiz, a paleontologist, published a description of the
genus now called Carcharodon with some precision in a catalogue of
fossil fish, naming the living species as Carcharodon smithii. He
had adopted the new generic name following the British naturalist and
physician Dr. Andrew Smith who had, at some time whilst resident in South
Africa between 1820 and 1836, procured a small white shark specimen from
the Cape Province region. Smith was the first scientist to properly
distinguish the genus and proposed the generic name Carcharodon in
an 1838 work by the German anatomists, Johannes Müller and Fredrich Henle.
In an 1839 discussion of white sharks, Müller and Henle again followed
Smith's generic name and called the fish Carcharodon rondeleti.
They suggested that the South African shark was somewhat different
from other white sharks and might thus represent a second species.
As it happened, Andrew Smith was to personally describe his specimen in
a later publication of 1849, naming it as Carcharodon capensis in
reference to its capture-locality. He mentioned stomach-contents and noted
aspects of white shark behaviour with an air of reality far divorced from
the mediaeval-inspired writings and mythos that existed before. In 1851,
J.E. Gray synonymised Smith's animal with C. rondeleti, realising
that this was one and the same species, rather than a unique South African
endemic. This assertion has been followed ever since.
For decades, Smith's stuffed C. capensis holotype - a juvenile
female measuring just over 2 metres in length - lay gathering dust and
more than a few errant white paint-splashes in the storage basement hall
of the British Museum of Natural History, London - until re-discovered
there in June 1994 by Leonard Compagno, Oliver Crimmen (of the museum's
Fish Section) and the author. Manoeuvring the hefty specimen down from
it's ceiling-high resting place on a top shelf, and then lifting it up two
flights of stairs to a laboratory, was an exhausting episode taking
perhaps more physical effort than the process of actually catching it in
the first place. Despite showing its age, the shark still had a legible
pencilled label affixed to its wooden base, reading "Carcharodon
capensis, Cape Seas". Preservation was sufficiently good to even see
the black axillar blotch beneath each pectoral fin insertion. The anal
fin, however, was missing - perhaps accidentally destroyed during the
mounting process.
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• Status and Biological
Summary
Arguably
equalled only by the killer whale (Orcinus orca) as a marine
macropredator, the great white shark occupies a cosmopolitan range
throughout temperate seas and oceans and will occasionally penetrate
tropical zones. Principally an epipelagic dweller of neritic waters,
Carcharodon is found from the surfline to well offshore, at the
surface and to depths over 250m on the bottom; commonly patrolling small
coastal archipelagos inhabited by pinnipeds , rocky headlands where
deepwater lies close to shore and offshore fish reefs, banks and
shoals.
Description
Adult female specimens of Carcharodon
carcharias (Linnaeus, 1758), above; and below, the shortfin mako
Isurus oxyrinchus (Rafinesque, 1810). Note morphological
differences in respective medial fin positions and pigmentation in living
specimens. Juveniles of Carcharodon are regularly confused for the
shortfin mako. (Illustrations © Ian K. Fergusson).
A fusiform, heavy-bodied shark with a crescentic caudal fin and large,
triangular, coarsely serrated teeth. In juveniles under 1.8 m, the teeth
have small lateral cusplets and in neonates, anterior lower-jaw teeth may
essentially lack marginal serrations. Typical tooth-count is:-
13 / 11-12
The snout is conical, blunt and dorsally flattened; the five gill-slits
are large but not encircling the head. The first dorsal fin, nearly an
equilateral triangle in shape with a slightly concave rear margin, has its
origin opposite, or slightly anterior, to the inner corner of the pectoral
fins. The first dorsal is rounded at the apex in neonates but becomes more
acutely-pointed within the first two years. The second dorsal fin is
minute and pivotable, its posterior margin above or slightly ahead of the
origin of the equally diminutive anal fin. The broad, dorsoventrally
depressed caudal peduncle is expanded laterally to form a prominent keel
on either side, but without secondary keels on the ventral caudal lobe
itself (as in the porbeagle Lamna nasus). The lunate caudal fin tends to
have acutely-pointed tips in sharks over 2.0 m TL. In neonates, the lower
(ventral) caudal surfaces may be more rounded and compressed but rapidly
expand soon after birth. The caudal lobes are almost of equal size, with
the lower (ventral) anterior margin measuring 76-92% of the same
measurement on the upper (dorsal) lobe. The pectoral fins are large and
moderately falcate.
• Colour
White sharks vary from
almost black to slaty-grey or dun above, with the ventral surfaces
predominantly white. A strong, variable line of demarcation separates the
dorsal and ventral surfaces with associated blotching, particularly near
the gill-slits and above the pelvic fin bases. Small, irregular dark spots
may be present on the flanks posterior to the 5th gill slit and the
lateral surfaces have a bronzy sheen that may be structural and manifested
only in strong sunlight. The ventral tips of the pectorals are black and
most specimens exhibit a black oval blotch in the axil of the pectoral
fin. The pelvic fins may be blotched with olive or grey; likewise the
ventral caudal lobe, with white marks and white anterior booting. The mode
of these demarcations vary greatly individually, but may exhibit common
trends amongst sharks in a given geographical remit. The variance in
dorsal pigment and tone is also very variable, especially between centers
of abundance but also within them. Californian examples are often very
dark slate-grey above, almost black. South African examples (Cape
Province) tend to be somewhat more dun or olive, as do Australian
specimens (but with much variance). Mediterranean specimens are
predominantly slate-grey or dark olive-brown dorsally.
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Size and
Reproduction
The maximum size attained by white sharks
remains a matter embroiled by debate and spurious information. Adult
females can reputedly attain 7 metres based on an unconfirmed
specimen from Kangaroo Island, Australia, taken in 1987. A further female
taken off Filfla, Malta, in the same year was reported as 713cm TL by
local sources but can be demonstrated, on the basis of a previously
unexamined photo scrutinised in October 1998, to be considerably smaller
at circa 530cm TL. It is realistic to suggest that maximum length of this
species actually lies in the range of 550 to 600 cm TL. The smallest
free-swimming examples, on the other hand, appear to be ca. 120cm TL.
Lengths at maturity for both sexes remain somewhat undetermined, and
based on (currently limited) age-growth data it may be possible that
different populations mature at varying lengths. The majority of females
mature at between 450-500cm TL (Francis, 1996), but have been reported as
immature at sizes as much as 472cm (Springer, 1939). Males mature at about
350-360cm (Pratt, 1996). A single study of age and growth, pooled from 21
specimens (Cailliet et al., 1985) suggests a generalised age of maturity
of 10-12 years. A mature female of 500cm is estimated to have reached ca.
14 to 16 years.
• Weight-at-Length
relationship
A recent allometric (size-on-size) equation for
weight (W) versus total length (TL) is given by Henry Mollet and Gregor
Cailliet (1996):
In W= 2.0686 + 3.0958 In TL (W in kg, TL in m)
y on x regression: In W= 2.1154 + 3.0542 In TL (N = 327; r2 =
0.973)
A further WT-TL regression was given by Compagno (1984), based on 98
specimens (mainly from California, with a range of 127 to 554cm):
WT = 4.34 x 10-6 TL 3.14
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•
Reproduction
Until very recently,
biological knowledge of white shark reproduction was simply informed
conjecture, based largely upon comparisons with other better-studied
Lamniform sharks such as sandtigers and porbeagles. Records of pregnant
white sharks in the literature were effectively confined to a single
Mediterranean report by Norman and Fraser (1937), who discussed the
capture of a 4.3 metre pregnant shark, reputedly a great white, taken in
the summer of 1934 off Agamy Beach at Alexandria, Egypt. The shark
contained 9 embryos, each about 61cm in length. Their account raises some
doubts over the accuracy of their original information and perhaps the
identification of the species. There was dearth of new information until
1985, since when six pregnant females have been verified and seven more
reported. Pacific records make up the majority, and include four from
Japan: a 555cm great white from Kin, Okinawa, taken on February 16 1985; a
ca. 470cm example from Taiji, Wakayama, on April 2 1986; a 480cm specimen
off Uchinoura on May 14 1992 and a 515cm shark from Toyo-cho, Kochi,
captured a few days later on May 22 (Uchida et al., 1996). A 530cm white
shark containing 7 full-term foetuses was taken on November 13, 1991 at
North Cape, New Zealand (Francis, 1996). As if to offer some contemporary
credibility to Norman and Fraser's report, the Mediterranean offered-up a
pregnant female in the shape of a five-metre-plus specimen taken in a tuna
net off Sidi Daoud, on Tunisia's Cape Bon, in the summer of 1992. She
contained two foetuses when eviscerated at the quayside, but may have
aborted more of a larger litter during capture (Fergusson, 1996). Further
recent but unconfirmed reports of pregnant white sharks originated between
1981 and 1996 from Queensland and South Australia. Three embryos of
ca.100cm were taken from a large great white caught near Taiwan in
February or March 1988, and off South Australia two embryos (one of 127cm)
were found during March 1994 in a net - probably aborted by the mother,
which had escaped, leaving a large hole. A very large female, reputedly of
640cm TL and containing five embryos, was taken 5 miles off Malindi,
Kenya, in early August 1996 (Rodney Salm, IUCN, pers.comm) and is
confirmed by good photographs, although no photos of the litter have come
to light.
Verified litter-sizes have ranged from 5 to 10
near-term foetuses, with unconfirmed reports of up to 14 embryos. Size at
birth, based on examined foetuses and free-swimming neonates, is within a
range of 120-150cm TL. The reproductive mode is viviparity without a
placenta and embryos are nourished by oophagy - the ingestion of
unfertilised eggs. Whilst in-utero, the embryonic white sharks swallow
their own sets of shedded teeth, perhaps to re-utilise calcium and other
minerals. Gestation times are unknown but doubtless long - close to a
year, perhaps. It is possible that any one female only reproduces
biennially, mating soon after giving birth, but this remains to be
confirmed.
Some incidents of fresh and healed bite-marks found
on the dorsum, flanks and particularly the pectoral fins of mature female
white sharks has been interpreted as an indicator of mating activity,
wherein males have grasped the female during copulation (as witnessed with
other species of sharks). Copulation has not been reliably witnessed in
this species, although an observation was reported by a volunteer seal
researcher describing the curious surface behaviour seen between two great
whites off the Nuggets, on the Otago Peninsula of New Zealand's South
Island, that may have been mating (Francis, op. cit.).
Scrutiny of worldwide records of pregnant females,
coupled with the localised, seasonal abundance of newborns, suggests that
parturition occurs during the Spring to late Summer in temperate shelf
waters. Areas where large adults of both sexes and neonates occur
together, indicating their likely significance for reproduction and as
nursery-grounds, include the shelf waters off the Northeastern United
States (the Mid-Atlantic Bight); Southern California and Baha; Southern
and Eastern Australia; New Zealand; Japan; Eastern Cape Province of South
Africa and the Southern-Central Mediterranean Sea, especially the waters
between Western Sicily and Tunisia. Young white sharks of a year-old or
less have also been caught elsewhere in the Mediterranean - off Algeria,
France and in the North Aegean, for example. The majority, however,
originate from the Sicilian Channel during high summer, when
Sicilian-based trawlers net the young sharks on the seabed at surprising
depths of up to about 200 m.
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Distribution
White sharks occupy a cosmopolitan distribution throughout temperate
seas and oceans and will occasionally penetrate tropical zones.
Sporadically, they make incursions to cold, boreal waters and have been
recorded from off the south Alaskan and Canadian coasts (Gulf of St.
Lawrence). Principally an epipelagic dweller in neritic waters, the white
shark is found from the surfline to well offshore, often in association
with isolated islets and archipelagos inhabited by pinnipeds (e.g., the Farallon Islands, Marin Co., California; Neptune Islands and
Dangerous Reef, Spencer Gulf, South Australia; Dyer,
Seal and Bird Islands, South Africa), rocky headlands where deepwater lies
close to shore (California and Oregon coasts; Central Chile; Ligurian Sea,
Italy), or near offshore fish reefs and shoals (e.g., Adventure Bank,
Sicilian Channel; Struis Bay area, Cape Agulhas, South Africa).
A synopsis of confirmed worldwide occurrences are listed below by
geographic region. Indices of relative abundance (based on
capture-records, sightings, interactions with man) are abbreviated thus:
CA: Center of Abundance F: Frequent; O: Occasional; I: Infrequent; R:
Rare; VR: Very Rare. Further remarks are added where relevant.
Northwest Atlantic and Caribbean:- Gulf of St Lawrence,
Newfoundland, St. Pierre Bank, Sable Island, Bay of Fundy (O-R); New
Brunswick, Maine, Massachusetts, Rhode Island, Martha's Vineyard, Long
Island, New York coastline and offshore, particularly within the 30-fathom
contour (CA; F); south along US coast through the Carolinas to Florida
(R-O). Gulf of Mexico, principally western Florida shores (I) but ranging
past the Mississippi Delta to at least Corpus Christie, Texas (R);
Caribbean occurrences - Florida Keys, Cuba (Cojimar), Bahamas
(R).
Literature: Pratt and Casey (1985); Bigelow and Schroeder
(1948); Schroeder (1938, 1939); Springer (1939); Piers (1934); Scattergood
(1962); Scud (1962); Day and Fisher (1954); Templeman (1963); Guitart and
Milera (1974).
Southwest Atlantic:- Central and Southern Brazil (R-VR), 10
examples known to 1993 of which 6 were from Rio de Janeiro State, 3 from
Ceará State and 1 from Espírito Santo State; Argentinean coast at Puerto
Quequén (Necochea) and south to at least C. Blanco (R).
Literature:
Siccardi et al. (1981); Gadig and Rosa (1996); Gadig, pers. comm.
Northeast Atlantic:- Charente-Maritime coast of France (La
Rochelle and Pertuis d'Aintoche; VR), north to the mouth of the Loire (VR,
1 old record); Gulf of Gascogne, Northern Spanish and Portuguese coast
southwards to Tarifa and Gibraltar (VR). Azores Archipelago (I); Madeira
(VR). Morocco, Mauritania, to Senegambia (Dakar region at Île de Gorée and
environs), Ghana and Cape Verde Is. (R). Canary Islands at Gran Canaria
and Tenerife (VR?); probably Lanzarote. Possibly Zaire but literature
confusion likely with bull sharks, Carcharhinus
leucas.
Literature: Quéro et al. (1978); Cadenat and Blache
(1981); Fergusson (1996); Ellis and McCosker (1991, for Azores).
Mediterranean Sea (CA): Spain and Balearics, including
Catalon Sea at Valencia, Vinaroz and Islas Columbretes; also recently
(1992) from Tossa de Mar and Andraitx, Majorca; Cabo Salinas, Majorca;
Menorca (R). Gulf of Lyons, particularly Sète, Palavas and Grau-du-Rois
(I-O); Riviera and Côte D'Azur (I), Ligurian Sea, especially from Camogli
and Portofino to La Spezia (O-R). Western Italy (Tyrrhenian Sea: Elba,
Anzio, San Felice Circeo, Ponza, Lipari Islands, Naples, Calabria Region),
Corsica, Sardinia, especially northern part at Capo Testa; southwest
region at Isola di San Pietro (O); Morocco and Melilla (O); Algerian coast
(I-O?), Tunisia, principally La Galite Islands, Cape Bon area and Gulf of
Gabès near Kerkennah Islands and Djerba (O), Sicily (cosmopolitan,
especially Egadi Islands, Trapani Region and Messina); Sicilian Channel,
Pantelleria, Isole Pelagie and offshore banks (F-O); Malta and Gozo (I).
Ionian Sea off Calabria (Capo Spartivento) and Galipolli. Southern and
Central Adriatic off Puglia, Manfredonia, Ancona and Termoli; also
Dalmatian coast near Split (I-O), Northern Adriatic, principally Istria
and Kvarner Gulf of Croatia (I, formerly F), sporadically at Riccione,
Rimini and in the Gulfs of Venice and Trieste. Corfu, Greek Mainland,
Aegean Sea (Thermaikos Gulf, Thassos, Kavalla, Alexandroupolis) through
Turkish coast (Foça region) to Bosphorus (R) but not Black Sea. Cyprus
(O), Israel ('Akko) and Egypt (Agamy, near Alexandria)
(R).
Literature: Doderlein (1881); Lozano Rey (1928); Tortonese
(1956); Postel (1958); Bini (1960); Capapé et al. (1976); Fergusson (1995,
1996); Mojetta et al. (in press). See Bibliography for detailed listing.
Southeast Atlantic:- Gough Island (single recent record).
Namibia, from Cape Cross and Swakopmund southwards (O, but little data)
possibly north to mid-Angola?, entire Cape Province, especially eastwards
of the Cape of Good Hope in False Bay, Walker Bay, Gansbaai, Danger Point,
Kleinbaai, Dyer Island group (CA; F), Cape Agulhas region (Struisbaai, Die
Mond, Arniston) and entire Wild Coast (F) to Port Elizabeth; Algoa Bay
(especially Bird Island) to Natal (F); northerly extent of range along the
Indian Ocean coast of Africa uncertain.
Literature: Bass et al.
(1975); Cliff et al. (1989); Compagno (1991 and pers. comm); Compagno and
Fergusson (1994); Levine (1996); Smith (1951).
Indian Ocean:- Northern Natal coast (F) but more sporadic
towards tropical extremes, perhaps more extensive around Southern
Mozambique and Madagascar than previously supposed, based on recent
sightings. Kenyan coast at Malindi; limits to northerly range in Western
Indian Ocean currently unclear. Appears absent in the Red Sea (one old,
doubtful record) or a very occasional outlier at best. Kuwait coast and
Persian Gulf (VR); Seychelles Island (VR), Cargados archipelago (VR); Sri
Lanka (VR).
Literature: Cliff et al. (1989); Khalaf (1987);
L.J.V. Compagno (pers. comm.); R.V. Salm (pers. comm.).
Indo-Pacific and Western Pacific:- Kamchatka region (VR,
possibly dubious), Japanese Islands (Honsu and Hokkaido, including Inland
Sea) (CA; O); Okinawa (I), Eastern Chinese Coast (VR), Korean Peninsula at
Pusan (VR), Taiwan at Keelung (VR); possibly South China Sea along the
Chinese coast and off Hong Kong (VR, dubious); Coral Sea (VR); Philippines
(Palawan, Mindanao) and Bonin Island (VR). Australia: Queensland (F-O),
entire coastline to NSW and South Australia (CA; F), Tasmania (F-O), Great
Australian Bight (CA; F), Western Australia (CA; F-O). New Zealand, both
North and South Islands (CA; O), particularly Dunedin, Otago peninsula and
environs on South Island (F-O). Stewart Island, Chatham Islands (O);
Campbell Island, recent attack there upon a diver (I-R?). New Caledonia
(VR).
Literature: Nakano and Nakaya (1987); Uchida et al.
(1996); Bruce (1992); Last and Stevens (1994); Francis (1996); Ayling and
Cox (1982); Cappo (1988).
Central Pacific:- Hawaiian Islands off Oahu, Hawaii and
Northwestern Islands (R); Marshall Islands at Bikini (VR); Easter Island,
based on recent shark attack.
Literature: Taylor (1985; 1993);
G. Burgess (pers. comm.).
Northeast Pacific:- Gulf of Alaska (VR), British Columbia,
Washington State (R), Oregon Coasts (O), abundance increases southwards to
Northern California (CA; F), Central California (CA; F, particularly from
Sonoma County, Marin Co., the Gulf of the Farallones, Año Nuevo Island,
Santa Cruz, Monterey Peninsula to the Big Sur); Southern California and
Channel Islands (CA; F-O), Baha and offshore at Isla de Guadalupe (O). Sea
of Cortez (I-R), Mexico (R) to Panama (R).
Literature: Klimley
(1985); Royce (1963); Pike (1962); Fitch (1949); Kenyon (1958); Follet
(1966); LeMier (1951); Kato (1965); Bonham (1942).
Southeast Pacific:- From Panama south through Ecuador and Peru
to Chile; data sketchy, however, for range north of Chile. Northern and
Central Chile (CA; O) to Archipelago de los Chonos (45úS), possibly more
southerly to Cape Horn.
Literature: Engaña and McCosker
(1987)
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•
Abundance
Overall population estimates for this species are
unknown and even regional or localised estimates are sketchy. Inter-annual
abundance of these sharks can be very variable and unpredictable, giving
rise to 'good' and 'bad' years, in a colloquial sense, for great white
numbers, albeit that the causal factors are essentially unknown. After
field observation and tagging work, Rocky Strong et al. (1996) calculate
the number of white sharks frequenting the Dangerous Reef area of South
Australia at circa 200 animals. On a wider level, some landings data is
available to (very roughly) indicate the proportional abundance of white
sharks, when compared to other species. Game fishery captures of sharks in
S.E. Australia between 1961 and 1990 indicated a catch-ratio of great
whites of 1:22 in the 1960's, declining to 1:38 in the 1970's and 1:651 in
the 1980's (Pepperell, 1992). South Australian game fishery catches from
1980-1990 averaged 1.4 sharks per year and has declined since the 1950's,
possibly through a reduction in effort (Bruce, 1992). Off the eastern USA,
National Marine Fisheries Service statistics from 1965 to 1983 show a
decline in ratio from 1:67 to 1:210 (Casey and Pratt, 1985). Other indices
of catch-rates are available from: a) California, between 1960-85 as 0 to
14 sharks per year (mean 3.2; Klimley, 1985); b) Natal, between 1974-88 as
22-61 sharks per year (Cliff et al., 1989); c) Central Mediterranean Sea
(Sicilian Channel), between 1950-94 as 0-8 sharks per year (mean 2.2,
author, unpublished data). In other areas such as Brazil and Hawaii,
captures are much more nominal and sporadic over time.
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• Movements and
Nomadicy
Occurrences are known within a wide sea-surface
temperature (SST) range of ca. 7.0 to 26ûC, but the species seems most
frequently encountered in temperate waters between 13 to 20ûC. Patterns in
movement and abundance within some areas (e.g., the seasonal position of
the 15ûC isortherm in the Northwest Atlantic [Casey and Pratt, 1985])
appear linked with seasonal variations in sea surface temperature, as
warmer waters influx poleward towards the northern limit of regional white
shark distribution. However, temperature may have only a limited effect on
the distribution of these sharks. An anomaly in white shark distribution,
at least on face-value, is their absence (or extreme scarcity) within
temperate coastal waters of Atlantic Europe - despite suitable habitats
and prey (including seals) being available to them.
Tracking of white sharks by telemetry has afforded an insight into
facets of their spatial behaviour, both in the horizontal and vertical
sense. An efficient, graceful cruiser at slow speeds (averaging 3.2km/h
over a distance of 190km, in a classic experiment off New York by the late
Frank Carey et al., 1982), the white shark, in keeping with other lamnids,
maintains elevated temperatures within the swimming muscles, brain, eyes
and gut to at least 13.7ûC above the surrounding sea temperature - an
adaption which may provide an increase in neural, digestive and muscle
activity and function. The species is also capable of short-duration,
high-velocity pursuits, even launching entirely clear from the surface in
spectacular repeated leaps. 'Blind' traditional telemetry and more recent
remote videography using parasitic 'Crittercam' video cameras reveals that
white shark predominantly cruises in a purposeful manner, either just off
the bottom or near to the surface, but spending very little time at
midwater depths unless stimulated by baits (Strong et al., 1992; Goldman
et al., 1996; Greg Marshall, pers. comm.).
This species is freely capable of making long-distance movements on
localised, regional and intercontinental scales. Although information is
rather limited by the essential rarity of these animals, some data on
movements has been afforded through tag-and-release programmes in America,
South Africa and Australia. For example, two white sharks tagged by a
joint Cousteau Society and South Australian Department of Fisheries (SADF)
Team near Dangerous Reef were later recaptured some 220km to the east,
near Antechamber Bay on Kangaroo Island. Similarly, a South African
specimen was found to have travelled approximately 780km in just 28 days.
But whilst tagging has demonstrated these rather long-distance movements,
the same studies have also highlighted an interesting propensity for white
sharks to exhibit a high degree of localised, temporary residency. At the
Farallon Islands, a stark archipelago some 40km due west of
San Francisco, researchers have identified a number of individual adult
white sharks through distinctive body-markings and fin abnormalities -
rather as accomplished in equatable studies of whales and dolphins. Over
the course of successive yearly field studies on the island since the
early 1970's, it has been shown quite conclusively that some of the
Farallon sharks return to the locale annually in the Autumnal months,
often arriving and departing on virtually the same repeated days or weeks
with surprising homogeneity. White sharks are scarce at the islands
between January and September, but precisely where those seen in Autumn
move away to through the remainder of the year is presently unknown.
Comparable recent work at Dyer Island,
South Africa and Dangerous Reef has yielded similar results to the
Californian study - some tagged (and thus readily identifiable) sharks
returning repeatedly to the same places, where they are then resighted by
observers with considerable frequency. Nevertheless, an even greater
proportion of tagged sharks are never resighted again - testimony to the
nomadic side of these fish.
Equally, it is clear that voyages by
white sharks can cover great distances. Although primarily occupying and
journeying within continental and insular shelf habitats, some white
sharks - and generally individuals from the larger size classes -
undertake long-distance journeys across the great ocean basins. They have
been found, albeit sporadically, both in mid-Atlantic at the Azores
archipelago and mid-Pacific at the Hawaiian Islands. Nominal captures have
also been reported from other discrete oceanic locales - including Gough
Island in the South Atlantic and Bikini Atoll in the Pacific's Marshall
Islands, as well as rather more captures from pelagic gillnetting
operations for squid in the epipelagic zone of the North Pacific. There is
no evidence to suggest that these treks have some reproductive
significance and the occurrence of white sharks at any one of these
localities is very variable in terms of both numbers, seasonality and bias
of gender. Taylor (1985, 1994) suggested that white sharks may frequent
Hawaiian waters through some predatory interrelationship with humpback
whale calving cycles. A similar hypothesis of a relationship between white
sharks and sperm whales may be applied to explicate occurrences at the
Azores, although in both cases this is very tentative. It is equally
likely that the phenomenon simply manifests the opportunistic, nomadic
behaviour of some larger white sharks - a trait that may conceivably
increase with older individuals that can readily subsist on large oceanic
bony fishes, cetaceans and other sharks. Whatever the case, these records
demonstrate that despite the wide geographic separation between known
centers of abundance, the white shark's distribution cannot be considered
as disjunct. For example, inter-hemispherical movement between temperate
areas, whereby white sharks traverse very warm equatorial zones, is
plausible. A possible mechanism is tropical submergence, where the shark
descends into and travels within deeper, cool oceanic waters across the
equatorial zone. However, white sharks also occur in shallow inshore and
offshore waters in the tropics and may may not need to use this mechanism
unlike some epipelagic and deep-water sharks.
So there appear to be
two sides of the same coin: the nomadic, 'just passing through' style of
spatial behaviour and the more systematic pattern of repetitive
occurrence, as demonstrated at select sites such as the Spencer Gulf, the
Farallons, and the Dyer Island Channel by tagging and field observation.
Clearly, the populaces of these 'classic' white shark localities are in a
state of continual flux, with numbers of sharks on any one day comprising
both 'resident' individuals and short-term nomadic visitors, and with all
of them moving around and seldom staying close to observers. It is
suspected that some white sharks occupy and patrol a favoured home range
in the broad sense of the word (particularly some large individuals at
Farallons), and that a proportion of attacks on divers are actually an
aggressive if limited response to the invasion of this 'personal space'.
The issue of white shark spatial behaviour is an enigmatic topic, whose
secrets may ultimately be revealed through current advances in electronic
tagging, data-logging tags, seabed-monitor arrays and long-distance
satellite telemetry..
[Back to CONTENTS]
Predatory Biology
The white shark is a formidible macropredator, with its
primary prey marine vertebrates and its most important prey bony fishes,
cartilaginous fishes, and marine mammals. Smaller sharks are primarily
piscivorous, but with growth the maximum prey size becomes larger and
larger juveniles and adults feed on a wide variety of small
to large bony fishes, elasmobranchs, cetaceans, and pinnipeds as their
principal prey, with other marine vertebrates and invertebrates also
taken. Fish prey recorded from across the size-range of this species
includes a number of elasmobranchs, such as juvenile dusky sharks, sandbar
sharks, tope, spiny dogfish, smoothhounds and other houndsharks, bronze
whalers, milk sharks, and blue sharks, shortfin makos, sandtigers,
scalloped hammerheads, whiptailed stingrays (Dasyatidae), batrays, eagle
rays, guitarfish (Rhinobatidae), wedgefishes (Rhynchobatidae), and
elephantfish (Callorhynchidae). Bony fish taken include bluefin tuna,
Atlantic bonito, albacore, bullet tuna and other scombrids such as frigate
mackerel; hake, bluefish, swordfish, sardines and other herring-like
fishes, sturgeons, sea catfish, cabezon, lingcod, rockfish, sea breams,
croakers, jacks (Carangidae), barracuda, striped bass, Pacific salmon,
halibut and flounders, and even ocean sunfish. Marine reptiles are
sporadically ingested, and within Mediterranean waters white sharks have
been caught with the remains of Loggerhead Caretta caretta and
green turtles Chelonia mydas in their stomachs (Fergusson et al.,
in press). Cephalopods (such as squid and cuttlefish), gastropods and
crustaceans are less important prey but benthic crabs may be ingested in
suprising numbers by large sharks, which don't necessarily spurn small
prey.
The role of Carcharodon as a primary predator upon
marine mammals, particularly pinnipeds, is oft-cited but sometimes
overemphasised versus the fish components in its diet. It is sometimes
stated that larger sharks switch to pinnipeds as prey and are narrowly
dependent on them, but this is apparently erroneous. In areas where
pinnipeds are abundant and sympatric with white sharks, such as along the
coasts of California, the Cape Province of South Africa,islands off South
Australia, and the Otago region of New Zealand, these sharks will lurk off
haul-outs and prey upon a variety of species including northern elephant
seals Mirounga angustirostris, fur seals Arctocephalus spp.,
harbour seals Phoca vitulina, grey seals Halichoerus grypus,
and sea lions including California sea lions Zalophus californianus
and Australian sea lions Neophoca cinerea. The dynamics of such
predator-prey relationships have been the focus for recent Californian
studies, primarily at the Farallon Islands (Ainley et al., 1981; 1985;
Klimley et al., 1992 and 1996) and at Año Nuevo Island, a low, sandy
feature north of Santa Cruz (Le Boeuf et al., 1982; S. van Sommerman,
pers.comm.). Similar field studies have been pursued off Cape Province,
South Africa, by the Shark Research Center (SRC) of the South African
Museum.
Cetaceans - and especially dolphins - are a common
prey-item in the Mediterranean and elsewhere, including within regions
where pinnipeds also occur and are preyed upon (e.g., Spencer Gulf of
South Australia; Bruce, 1992;Western Cape, South Africa). Taken
free-swimming and opportunistically scavenged from the nets of fishermen
and beach meshing programmes, dolphins are known to fall prey to great
whites off South Australia (Bruce, 1992), Western Australia (Cockeron et
al.) South Africa (Cliff et al., 1989; Compagno, 1991) and in the
Mediterranean (Postel, 1958; Fergusson, 1994). In the latter area,
bottlenose dolphins Tursiops truncatus are the most frequent prey
species. Other odontocetes (toothed whales) taken by these sharks include
common dolphins Delphinus delphis off Tunisia (Postel, 1958),
harbour porpoises Phocoena phocoena in the Canadian Atlantic
(Arnold, 1972), pygmy sperm whale Kogia breviceps and Dall's
porpoise Phocoenoides dalli off California (Long, 1992; 1996); also
dusky dolphins Lagenorhynchus obscurus and Indo-Pacific humpback
dolphins Sousa plumbea within other regions. The carcasses of great
whales are readily scavenged by white sharks in feeding aggregations off
Long Island (e.g., Carey et al., 1982; Pratt et al., 1982), California (P.
Pyle, pers. comm; R. Collier, pers. comm), South Africa and elsewhere.
This interrelationship between white sharks and cetaceans is by no means a
new one - scars attributable to these sharks have been found marking the
fossilised skeletons of bottlenose dolphins (see Cigala Fulgosi, 1990, for
a detailed example from Italy) and cetotheriid whales (Demere and Cerutti,
1982).
Interestingly, the white shark will often bite, but rarely
ingest, two groups of prey. Firstly, seabirds - particularly jackass
penguins Spheniscus demersus on islands off the South African coast
- are commonly found to have suffered cursory injurious or mortal
'grab-release' , 'slash' (apparently with the tips of the lower and upper
teeth), and 'bash' (with the upper teeth) bites from white sharks (Randall
et al., 1988; M.A. Marks, pers. comm.) but are rarely ingested. Other
avians including brown pelicans, cormorants, gannets and gulls suffer
similar fate, albeit not always culminating in some disabling injury. Ian
Fergusson witnessed an entire sequence at Dyer Island wherein a cormorant
(Phalacrocorax sp.) was grab-released by a white shark, commencing
with the surface-resting bird being taken suddenly by a leaping white
shark and carried airborne in its mouth, before being taken subsurface for
a few seconds. Much to his incredulity, the bird then re-surfaced and
flew-off, showing no visible sign of mishap after the impromptu
'slam-dunk' (Fergusson, 1995). Birds are also 'bounced' (sharks come up
underneath gulls and other seabirds sitting on the surface and send them
tumbling with an upward flip of their heads), and are either grabbed or
not. Sea otters (Enhydra lutris) are mortally injured by white
sharks off central California, especially near Monterey and Carmel (Ames
and Morejohn, 1980; Ames, 1996) but have yet to be found in white shark
stomachs. Exactly why birds and sea-otters are almost exclusively rejected
as prey is unclear, but perhaps this phenomena has some enigmatic bearing
upon the reasons why most human victims of white shark attack are also
released, usually after a very limited and non-energetic contact of a
nature that is at odds with the unquestionable power of these fish and the
massively traumatic and swiftly lethal nature of full-fledged feeding
attacks on similar-sized pinnipeds and other marine vertebrates. However,
even regular prey animals such as young of the year Cape fur seals may be
lightly grabbed by white sharks and released with little injury (M.A.
Marks, pers. comm.).
White sharks will scavenge from fishermens
nets and longlines and will take all manner of hooked fish, including
conspecifics, taken by rod-and-line. This propensity often results in
their own accidental entrapment. In Mediterranean waters and elsewhere, it
is because of this opportunistic behaviour that many white shark captures
are made by means of the predators scavenging large fish and other sharks
taken by longlines, or entrapped in gillnets, on setlines or other fishing
modes. In addition, large specimens are sporadically taken by swordfish
harpoons within the Straits of Messina, Sicily. Firm evidence of these
sharks scavenging fishery discard is afforded by the discovery of a 2
metre bottlenose dolphin carcass in the stomach of a 535cm white shark
taken at Favignana, Sicily, in May 1987. The dolphin remains, bitten
cleanly in two at the abdomen, were relatively fresh but clearly scavenged
- a tightly-knotted nylon rope was bound around the caudal peduncle, an
unmistakable sign that the mammal had been entrapped by driftnet, drowned
and then retrieved by fishermen. At the time, fearful of environmental
lobbying over cetacean mortality in these fisheries, local operators would
habitually sink dolphin carcasses by knotting rope around the tails and
attaching a stone anchor (Giuseppe Notarbartolo di Sciara, pers. comm.).
In all likelihood, this dolphin was ingested post-mortem by a white shark
which severed the carcass's anchor-rope during feeding.
[Back to CONTENTS]
Social
and Complex behaviour
Contrary to the lonely JAWS spectre of
an idiot eating-machine, the white shark is actually a social animal,
exhibiting a raft of complex behaviours. Intraspecific ethology and
sociobiology in this species are now receiving dedicated research
attention, and are considerably more complex than previously recognised or
embodied within the archetypal 'lone killer' image. Field-observations
have described pecking-orders at feeding aggregations at carcasses which
seem based upon a size-hierarchy (see Pratt et al., 1982), where larger
sharks dominate in eating; this has also been seen off South Africa with
floating baits, but is complicated by individual motivation. Some of the
great white's swimming-modes are interpreted as ensuring avoidance of
conspecifics and maintenance of a personal space, such as cautiously-timed
'turn-aways' between two animals converging on reciprocal approaching
courses. Similarly, the 'parallel-swim' mode is often seen, whereby two
sharks heading on the same vector retain an unfluctuating distance from
each other, again as what seems to be maintenance of personal space
(L.J.V. Compagno, M.A. Marks and I.K. Fergusson; personal obs. and in
press). What appears to be a non-injurious means of deflecting competition
whilst feeding at the surface has been observed off California and South
Africa, whereby white sharks strike or splash conspecifics with the caudal
fin in a spectacular exhibition dubbed 'tail-slapping' (Klimley et al.,
1996). White sharks will also shove or 'body-slam' other white sharks (and
boats) by lateral movements of their bodies, and also use their caudal
fins to strike boats and even observers aboard them (M.A. Marks, pers.
comm.).
Many white sharks, both adult and immature, have slash and
puncture wounds of superficial nature to the head and dorsum, which are
inflicted by the teeth of rivals during brief bouts of intraspecific
aggression and competition, especially near food resources but very likely
also through courtship or other social interactions. In the past, these
marks were almost exclusively explained as being caused by the flipper
nails or teeth of pinniped prey, but closer inspection and further
observation in the field largely excludes this theory. Aggression between
these sharks is very inhibited, considering the potential for severe
wounding or worse, and includes rather cursory bashing, slashing and
grab-release biting with both the upper and lower-jaw teeth. Where
elicited on inanimate items offered to white sharks, much of this casual
mouthing seems to be investigative rather than any attempt to ingest, and
the observer is left with an overwhelming image of the shark using its
fearsome jaws with very fine control for tactile sense and manipulation as
well as for actual feeding (authors, personal obs.). By the same token,
such rather low-intensity biting is typical in attacks on humans, with
puncture marks, as opposed to actual flesh removal, being commonplace.
Whilst white shark attacks are often explained through a process of
'mistaken identity' with natural prey, underwater observations suggest
that the sharks readily distinguish between humans and prey-animals such
as pinnipeds. A more compelling hypothesis is that many such 'hit and run'
interactions are motivated by interspecific aggression; perceived invasion
of personal space, or other motives not directly allied to feeding such as
'play'. As white sharks apparently interact socially by low-intensity
biting and grabbing, at least some oral contact with humans and other
animals that are not regular prey may have a social framework, with sharks
behaving with humans as they would with other sharks. Humans in such
interactions may not understand what the shark's body language (including
displays such as gaping and hunching) may signify (if they notice them at
all) and what responses are appropriate to the context, until the shark
proceeds further in the interaction and grabs the person. Work in progress
off South Africa suggests that white sharks as individuals and groups
confronted by free-swimming skin and SCUBA divers are usually not
aggressive even when baits and chum-trails are present but may investigate
the divers quite closely without showing any signs of perturbed, agonistic
behavior (M. A. Marks, pers. comm.).
White sharks attracted in
baited situations exhibit curious behaviours, such as inverted
surface-swimming with the mouth agape and gape-displays on the approach to
shark cages, divers and so-on, at least some of it being thwart-induced
(see Strong, 1996) or displacement behaviour, in a generic sense, as well
as int. This activity that is not unlike that observed with the shortfin
mako Isurus oxyrinchus. It may appear simply maniacal on films, but
such ethology must have a more deep-rooted purpose. In the gape-displays,
the palatoquadrate (upper jaw) is exposed for a protracted period during
non-feeding, rather akin to a dog snarling and bearing its canine teeth.
Indeed, its purpose may be exactly that of the dog - an agonistic threat
display that warns-off competitors or intruders of personal space with a
display of natural weaponry that requires little further explanation! Some
white sharks couple this type of behaviour to a unnaturally stiff swimming
mode, with pectoral fins held markedly downwards, and back slightly arched
('hunch' display) and accompanied by periodic gaping that may be directed
both intraspecifically (to other white sharks) and interspecifically (for
example, to people - but quite possibly, or probably, also to seals,
dolphins and other animals). The conspicuous dark axillar blotch
(highlighted by bare white axillar skin around it), which is only normally
exposed by the 'pecs-down' hunching style of swimming, may play a visual,
communicative part in this posturing. Notably, it is a feature of
pigmentation found on both white sharks and the shortfin mako (but not the
porbeagle or salmon shark) - suggesting that its role, if any, is
duplicated or at least overlapping in both species. It's occasional
absence as a feature on Mediterranean white sharks may be evidence of a
low population density, with very limited intraspecific contact; i.e., the
feature has been progressively lost in an adaptorial, evolutionary sense.
However, white sharks without axillary spots also occur off South Africa
and California where white shark numbers are greater and social contact
injuries are commonly seen on sharks. Whilst this explanation remains
totally speculative, the apparently low degree of contact between
Mediterranean great whites other than for reproduction is further
indicated by the dearth of scratches, stabs and other allied marks as seen
on the heads and anterior parts of these sharks in regions elsewhere (see
above).
[Back to CONTENTS]
Conservation of the great white shark
Threats
• Directed
Fisheries
In directed terms, white
sharks are primarily exploited for the curio trade, with jaws and
individual teeth fetching high prices on both local and international
markets; a recent large set of jaws from South Africa being valued at
$50,000. Often associated with these commercial ventures are
sportfisheries, as formerly undetaken in a high-profile manner off
Southern Australia, South Africa, and to a lesser degree in other regions
such as the eastern USA. Whilst a number of white sharks are taken
annually by rod-and-line charter-boats, a further, more unscrupulous
method employed by some operators involves passive-fishing by means of
large baited meathooks secured to anchored oil-drum floats by heavy-gauge
chains. These 'chain-line' and associated 'big hook' fisheries are
generally unstructured, unregulated or downright illegal; their aim being
solely the procurement of white shark jaws or teeth for trade. Individual
dentition removed from smaller white sharks may sell for a higher price in
aggregate than complete sets of small jaws, and the threat posed by the
curio-trade encompasses white sharks across the entire size and
maturity-range. This trade is not restricted to jaws and teeth; even
entire specimens, some attaining in excess of 5 metres, have been
preserved by freezing or taxidermy for static public display or as private
trophies and curios.
In some areas, the excellent, palatable flesh
of this species, rich in red muscle when properly filleted, can fetch high
retail prices for human consumption and considerably more than that of
other similarly-exploited sharks such as the shortfin mako Isurus
oxyrinchus. However, coupled equally to consumer disquiet over the
'maneater' tag, and the fact that white shark meat is not uncommonly high
in mercury, commercial use for human cuisine is geographically and
culturally patchy. Because very few specimens marketed by fisheries are
listed under species-specific landings statistics, consequently the
precise level of such exploitation remains poorly documented.
Some
rod-and-line sports fisheries have operated both on the Atlantic and
Pacific coasts of North America, but rarely are these directed solely at
white sharks. In the Mid-Atlantic Bight, juveniles are occasionally landed
in angling tournaments - some 140 specimens were taken in those waters
between 1971 and 1991, by tournaments and research vessels (Pratt, 1996).
In the past, big-game charters were run with some success to target adult
specimens in the same area. One operator, Frank Mundus of Montauk, Long
Island, was particularly active in this regard and his association with
catching big white sharks inspired the 'Quint' character in Peter
Benchley's JAWS. More opportunistic ventures, such as the harpooning of
sharks feeding on whale carcasses, was not unknown in the waters off Long
Island. The National Marine Fisheries Service (NMFS) now seeks to control
and outlaw targeted captures of white sharks in the northwest US Atlantic
(now supported by legislation enforced since early 1997) and has
successfully encouraged and coordinated the tagging and releasing of these
and other species of sharks for many years.
On the US Pacific coast,
white sharks have been targeted in the past off both central and southern
California, albeit with variable success. Particularly in the wake of
"Jaws" (1975), white sharks were a popular but somewhat elusive quarry for
anglers in Southern Californian waters. Their activities were frequently
inspired by the large cash rewards offered at the time by oceanariums, who
sought great whites (or bits and pieces thereof) for public display as a
cash-in on the 'Jaws-mania' of the era. Juvenile sharks were often taken
very close inshore and larger specimens fell victim to harpoon-wielding
hunters. More recently, in the mid-1980's, one-off opportunistic ventures
were undertaken to capture white sharks at the Farallon Islands near San
Francisco, a National Marine Sanctuary reknowned internationally as a
white shark locality. The virtually simultaneous capture of four sharks at
the islands in 1984 was met with dismay by the scientific establishment
and some sectors of the public and media. Since then, fishing-forays to
the islands or elsewhere in Californian waters in search of white sharks
have been outlawed by State Legislation SB-144.
[Back to CONTENTS]
• Indirect
Mortality and Beach Meshing
The propensity for white sharks to
scavenge from commercial longline and net fisheries makes them very
vulnerable to accidental entrapment. Worldwide, specimens are reported
annually from gill-nets, trammels, herring-weirs, purse-seines,
tuna-enclosures and hooked upon surface and bottom longlines and
set-lines.
Somewhat more directed pressure is manifested in the form of anti-shark
beach netting, installed to ensure the safety of bathers at selected
localities. Shark nets have been installed at some Australian beach
resorts in New South Wales since 1937, and along Queensland's Gold Coast
since 1962. Similar measures are taken in South Africa where in 1952,
responding to a series of high-profile local shark attacks, the first nets
were installed off Durban. This was followed by the installation of two
further nets at Amanzimtoti in August 1962. As of 1990, 14% of the 326 km
of Natal coastline between Mzamba and Richard's Bay was protected by 44.4
km of gillnets (Dudley and Cliff, 1993), with the operation controlled by
the Natal Sharks Board.
In the Queensland Shark Control Programme and NSW meshing operation,
there is data to indicate an irregular decline in white shark captures
over the past three decades. The Natal net-catches - a total of 591 white
sharks between 1974 and 1988, with from 22 to 61 examples caught annually
(Cliff et al., 1989) - indicates a similar but less clearly-defined
downward trend. Conscious of mounting environmental concern and criticism,
there is an increasing willingness by meshing contractors to tag and
release sharks found alive in the nets, although mortality remains high
overall both to sharks and other inoffensive marine creatures including
rays, guitarfish, dolphins and turtles. The broad effect of these meshing
programmes on marine ecology - not least because they are totally
unselective by its very nature - has created considerable controversy and
some current research is directed at developing harmless alternative
measures, such as electronic barriers to repel sharks.
[Back to CONTENTS]
• Habitat Loss or
Degradation
Being a highly mobile, pelagic species the
threat of habitat loss may appear generally minimal to white sharks.
However, disruption of prey availability poses potential threats and in at
least one area - the north Adriatic Sea - white shark captures and
sightings have declined markedly in the latter half of this century,
possibly through depletion of teleost prey stocks, dolphins and possibly
monk seals. All of these factors may themselves be the effects of
increased pollutants, overfishing or both. Despite this, white sharks are
adaptable predators capable of shifting diet as conditions dictate and may
simply cease inhabiting a degraded area and move elsewhere. As tagging
studies have demonstrated, these sharks can display a varying degree of
localised residency - a trait that may make them vulnerable to habitat
loss, at least within the short-term.
[Back to CONTENTS]
•Other
Factors
In recent years, cage diving for white sharks has
become an important 'spot' industry in some parts of the world, most
notably in Australia's Spencer Gulf (Dangerous Reef and Neptune Islands),
along the South African Cape Coast (especially at Dyer
Island) and to a lesser degree in the warm waters of Baja
California.
Originally, cage diving and white shark viewing blossomed in Australia,
following the success of early endeavours by filmmakers of the 1960's and
1970's including Ron and Valeria Taylor, Stan Waterman, Peter Gimbel and
others (e.g., Blue Water, White Death). South African efforts came
later through operations in False Bay and elsewhere on the Cape Coast, but
are arguably are now more prominent given that reported successes of
Australian 'pay-for-view' operations seemed to diminish in the 1990's, as
indeed did the Spencer Gulf's population of white sharks. In the 1990's,
Californian cage diving operations started opportunistically near Santa
Cruz but were banned by legislation in the wake of fierce local opposition
by surfers groups, scientists and others. All deliberate attraction of
white sharks in Californian waters has since been outlawed by state
legislation, and no cage diving operation directed solely at white sharks
now exists there.
In South Africa, a variety of commercial cage tour operators have
jostled for position and clientele - sometimes quite literally so - in the
narrow confines of the waters that separate Dyer Island from Geyser Rock.
In recent months, local conservation authorities and regulatory bodies
expressed concerns over the increasingly 'circus' atmosphere prevailing at
the locale, sometimes coupled with operator's indifference to the area's
status as a nature reserve, and the process has resulted in a temporary
moratorium on various white shark related activities there (see News piece for fuller description).Various activities that
could ultimately prove injurious to sharks, such as repeated biopsy
sampling, have been included in the temporary ban and all further
applications to pursue research at the islands must be first scrutineered
by local recognised experts (Chondrichthyan Working Group). The motivation
behind the current moratorium is perhaps best explained by Leonard
Compagno (pers.comm), who draws parallels to the protection of South
Africa's terrestrial predators. "If I were to pull-up in my car at Kruger
Park," says Compagno, "and start firing dart tags and such like at lions
or cheetahs, without any sort of research permit to so so, I'd be quickly
arrested." In other words, the current closely-guarded and vetted access
to lions, cheetahs and other terrestrial mammalian predators should be
quite properly extended to an equally protected marine piscine predator,
the white shark. Few would disagree with this rationale.
Whilst cage diving can clearly benefit the white shark in many ways,
and offer a more passive and profitable incentive to former game or
commercial fishermen, the South African example demonstrates that as much
attention should be given to vetting and licensing such activities as is
afforded to banning directed fishing itself.
[Back to CONTENTS]
Conservation measures
• Present and Planned action
The most significant problem in applying
definitive conservation measures in favour of white sharks remains the
lack of baseline data on basic parameters such as the fecundity, age and
growth and population-numbers of the species. Such data is particularly
difficult to obtain for white sharks, principally as they are generally
rare wherever they occur; esentially cryptic, and pregnant females are
scarcely captured let alone examined by fisheries workers.
Recruitment-rates for this species are unknown and tagging studies, until
recently involving unsuitable methodology for white sharks, provides data
that in this species takes a considerable number of years to amass as a
consequence of rather nominal recaptures and tag-returns. Current topical
thought, therefore, is that protective measures should be based on a
precautionary principle, until such time as more biological information
has been collated.
Protection in South Africa
It was
acting precisely upon such guidance that the South African Government
legislated to protect white sharks in April, 1991 - the first nation to
do-so. The crucial points that convinced Louis Pienaar, then Minister of
Environmental Affairs, to create a ban on the sale of white sharks or any
white shark product, were a number of arguments proposed in a
comprehensive review by Dr Leonard J.V. Compagno (Compagno, 1991a) and
others, strongly supported by Nan Rice of the Dolphin Protection Group
(who was instrumental in lobbying Environmental Affairs to protect the
white shark), which was circulated prior to a meeting convened by
Environmental and Sea Fisheries agencies on March 19th of that year. On
the basis of the report, the parties had essentially agreed on total
protection by the time of the meeting. It was stressed that: "....Because
the population size is likely to be small, this shark could be threatened
if exploitation by trophy-hunters increased, as appeared to be the case,
judging by the number of foreign enquiries about commercial shark hunting
safaris into Cape waters....The reproductive rate is low and the slow
growth and late maturity of this species makes it highly vulnerable to
over-exploitation..." (see Smale [1991] for a full summary, and Compagno,
1990, 1991a,b, for particulars of white shark protective measures in South
Africa). The legislation concerning protection of this species falls under
the National Marine Fisheries Act and covers the entire South African
coastline and EEZ. It mandates heavy fines, boat confiscation, and jail
sentences for anyone caught catching, killing or injuring white sharks, or
dealing in white shark products. Further legislation passed in 1998
tightens access to white sharks after problems were identified, with
research and ecotouristic shark cage diving by permit only and with a
limited entry for cage dive operators nationally and for favored sites
such as the Dyer Island Channel. Apparently the South African protective
action inspired the Namibian goverment to adopt similar protective
measures for the white shark in 1993.
Protection in
California
Similarly, a set of protective measures were installed
for Californian waters, after lobbying by scientists and conservationists
who found a political ally in Sacramento Assemblyman, Mr Dan Hauser.
Passed unanimously, State Assembly Bill AB522 was enacted on January 1st,
1994 and effectively prevented the development of directed sports or
commercial fisheries for white sharks in California until at least 1998.
It is instructive to note that the legislation received unequivocal
support from, amongst others, the California Urchin Divers Association and
Surfrider Foundation, both whose members figure in white shark attack
statistics. Current legislation concerning protection of this species is
State legislature SB-144 (1997) which replaces the temporary AB-522
enacted in 1994 and includes a clause to outlaw all directed efforts at
attracting white sharks either by use of baits, chum, or other
methods.
Protection in Eastern United States waters
After
California's action, the State of Florida followed-suit with unilateral
state legislation, However, in early 1997, all directed targeting of white
sharks other than tag-and-release sport angling was outlawed throughout
all US eastern coastal waters and the Gulf of Mexico as part of the
Fisheries Management Plan (FMP) enacted by the government's National
Marine Fisheries Service (NMFS).
Protection in Australian
Commonwealth waters
Despite the considerable efforts by many
individuals there, Australia had been slow to act in affording full
protection for white sharks but an increasing movement of public
shark-sympathy, supported by a number of scientific and conservation
bodies, ensured that it was a matter never far from media attention.
Although commercial fishing still presents the greatest threat to sharks
off Australia, it had been sportfishing - and especially for great whites
- that commanded the greater media and public attention. The South
Australian towns of Port Lincoln and Whyalla, on the shores of the Spencer
Gulf, have long been traditional locations from where big-game anglers
set-sail in search of the ultimate fishing trophy. And yet the sport was
under increasing threat as the mid-1990's approached, as evidence by
frequent public wrath at reports of white shark captures published within
the Australian newsmedia.
In May 1995, Jon Presser and Ross Allan
(1995) gave a discussion paper suggesting a series of conservation
measures for white sharks in South Australian waters, including
prohibition of chumming within 2 nautical miles of the coast, restriction
on fishing hook sizes, licensing of cage-viewing tours and the expansion
of conservation zones in the Spencer Gulf to restrict possible access to
white sharks. Central to these measures was the proposed full protection
of white sharks, under Section 42 of the Fisheries Act, 1982. Meanwhile,
more 'unilateral' precautionary protection to white sharks had been
enacted by the States of New South Wales, Tasmania, Queensland, Western
Australia and - at least in a partial sense - by South
Australia.
Through a joint press release issued on 22 December
1994, the Minister for Primary Industries and Minister for Environmental
Affairs acknowledged the need to provide greater protection for white
sharks and requested recommendations from the research community. Final
collation of this data was completed on July 28, 1995, with a view to
legislation being in-place before the end of the millennium.
On 17
December 1997, Federal Environment Minister Robert Hill announced that the
Australian Government was protecting great white sharks throughout all of
their Commonwealth waters, prohibiting all directed hunting, molestation
or harassment of the animals. Anyone wishing to capture a specimen for
'scientific purposes' must hold a government permit. The white shark is
currently listed as a Federal Endangered Species. The State of Victoria
enacted local species-specific legislation in 1998; meanwhile, the
Australian government has agreed to pursue a CITES proposal for the white
shark, to which various parties and individuals are currently (Dec. 1998)
offering input.
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Action
Required
In April 1996, a status report on the great white shark was prepared
for the World Conservation Union's (IUCN) 'Red List' - a published
compendium that details threatened animals and plants, offering the sort
of definitive information that may aid in the planning of conservation
strategies. That assessment (see Part 3) concluded that the fish should be
enlisted then under the banner of 'Vulnerable', but that given more data,
this category may change to "Engangered' on at least a regional basis. The
report also concluded that only a global solution will ultimately
safeguard this very global fish.
Although we know very little about
the global interrelationships of these sharks, it may be the case that
regional or national protective measures will not ultimately address the
long-term welfare of the species. Citing the west coast of North America
by way of example, the white shark can be assured of total conservation
only if Oregon, Washington and Mexico followed California's lead. The
potential ineffectiveness of unilateral measures is perhaps best envisaged
when one considers a white shark pupping and nursery-ground - the Sicilian
Channel. If measures were enforced solely in Sicilian (Italian)
jurisdiction, little effect would be manifested in the protection of
sharks only a few kilometres distant, in the seas off Tunisia.
Nevertheless, this is not to discourage such conservation efforts - far
from it. Unilateral or regional attempts to conserve great white sharks
are laudable, as they may provide the encouragement for neighbours to
adopt commensurate measures. The situation can change rather rapidly, as
was the case in Australia. At the time of writing, the Shark Trust and EEA
were pressing the Maltese Government to protect white sharks in their
coastal waters, and become the first Mediterranean nation to take such an
inportant step in the process. Such a high-profile move may even help
advance the long-delayed ratification of the Barcelona Convention, which
lists the white shark in it's appendices as an endangered fish, needing
urgent protection. 
The pitfalls of inadequate enforcement must be emphasised. Analogous to
the unlawful poaching of rhinos or tigers for traditional medicines, the
demand for procuring white shark carcasses can only be nullified through
equally stringent efforts to banish the market for their end-product
curios. Only pan-national legislation will provide this long-term
security, such as enacted through the jurisdiction of CITES enlistment. In
September 1998, representatives from the Humane Society indicated that
Australia would pursue a CITES enlistment for the white shark, a move
since confirmed and which deserves wider international support -
especially so from both South African and the USA. Given the traditionally
negative status of great white sharks within the public psyche, any
public-supported protection of this enigmatic nimrod is a ray of hope in
aspiring to conserve less well-known, less fearsome - but no less equally
threatened - elasmobranch species.
Proposed International CITES Listing: The way
forward?
Ultimately, the white shark's future can only be secured
through legislation enacted and enforced pan-globally. Thus, seeking a
listing within the remits of CITES protection is considered imperative
considering the wide-ranging habits of this fish.
Directed fishery
exploitation (mortality) of white sharks is primarily undertaken with the
aim of securing and trading its body-parts, especially teeth and jaws, as
trophies or curios. Recent information suggests that preserved jaws may
fetch from $10,000 - $50,000 in collectors circles, and there is good
evidence from a Scottish-based collector_ that white shark teeth and jaws
are still freely available from California and South Africa despite the
current trade embargos there. Anecdotal evidence supports the notion of
unlawful trade being undertaken in the latter nation's Cape Province
waters, with local commercial fisheries operations supplying international
offshore fishing vessels with white shark jaws and shark cage operators
being offered enormous sums for white shark jaws and isolated teeth.
Similarly, new suppliers have offered collectors white shark jaws from an
offshore fishery based at Mazara del Vallo (Trapani), Sicily, which
incidentally captures neonatal specimens. Some South American states are
emerging as a secondary source of collectable material, apparently pooled
from sharks caught off Baja and environs, where Mexican-based dealers act
as couriers.
The vulnerability of white sharks to curio-hunting is
poignantly comparable to previous exploitation of large terrestrial
predators for trophies, furs and so-on. All available evidence points to
these key facets in proposing the white shark for CITES listing:-
- The species is specifically targeted for trophies, saleable curios,
and fins for the oriental soup-fin trade. Current unilateral
restrictions of such activities, as exist in some parts of the species'
range, is presently the only curb upon such exploitation. The
effectiveness of such legislation is wholly reliant upon diligent
enforcement in those nations or states where it has been enacted.
Consequently their remains the potential for illicit trade and unlawful
fisheries to continue operating, not least fuelled by the high prices
paid by collectors for white shark jaws (as much as $10,000 dollars per
pair of jaws and with collectors apparently willing to pay far more for
jaws from large adults) and isolated teeth. Fin sets from large white
sharks are valuable for their size, being priced at hundreds or even
thousands of dollars, but also from their source, as white shark
notoriety apparently boosts values of their fins.
- There is growing evidence to suspect a global decline of white shark
populations due to a combination of causal factors which are poorly
understood, but which may include wide-ranging and largely unreported
bycatch from world fisheries (including major offshore operations), as
well as targeted fisheries. As the interrelationships, interchange and
recruitment between seemingly discrete populaces of this shark are
unknown, it is quite possible that regional mortalities have a much
wider knock-on effect in a global sense.
- Some areas where white sharks are periodically commercially targeted
for trophies, or have been so in the recent past, also serve as
preferred feeding habitats, nursery zones or other areas (white shark
'sites') and are believed important to reproductive behaviour and to
social interactions. The sharks readily investigate boats at these white
shark sites, and can be lured to within touching distance by chum and
floating baits. As a result, white sharks are rather easily located and
can be killed with rather modest effort and equipment (including
relatively small outboard 'skiboats') in comparison to their value.
- Given the wide areal range of white sharks, the limited geographical
protection as currently exists in South Africa, California, eastern USA,
Australia and elsewhere will not prevent dedicated exploitation shifting
to other vulnerable locations where such hunting is not outlawed and
white sharks are accessible.
- Geographically-limited or unilateral restrictions will not
ultimately curb the worldwide collectors market for white shark
products. There is evidence that existing laws are already being
violated, as discussed above.
The white shark story is one that charts the very worst of human
ignorance, indifference, insecurity and greed, where it destroys and
neglects our wildlife and environment. This is not a fish to be
underestimated. It is neither a bloodthirsty, mindless killer nor a
playful, good-natured puppy-dog. It is a sentient, intelligent predator
deserving of our rational respect like any other potentially lethal
animal. For confirmation of this, ask any fur seal...
© Ian K. Fergusson 1998
No Reproduction in any form
without express permission of the author.
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