GREAT WHITE SHARK

Since 1980, six pregnant females have been verified, taken from coastal waters off Okinawa and Japan; New Zealand and Tunisia.

Further recent reliable but unconfirmed reports originated during the same period from Australia, Taiwan, and most recently Kenya.

Reported litter-sizes range 2-10 foetuses. No reliable data is available of early- and mid-term embryos. Mollet et al. (2000) asssumed that the Kin, Okinawa, Japan specimen was early term because of the presence of over 200 eggcases in the uteri and that the Alexandria, Egypt specimen was mid-term.

Gestation time is unknown but likely to be long.

Size at birth is within a range of 120-150cm TL.

The reproductive mode is aplacental viviparity with embryos nourished by oophagy (ingestion of unfertilised eggs).

Contrary to some popular publications, this species does not exhibit 'uterine cannibalism' such as found in the sandtiger shark, Carcharias taurus.

Conceivably, females may give birth every two years rather than annually.

Birth apparently occurs during the spring to late summer in warm-temperate coastal waters.

Areas where mature adults and newborns occur together, indicative of reproduction, include the shelf waters of the N.E. United States, Southern California, Southern and Eastern Australia, New Zealand, Japan, Eastern Cape Province of South Africa and the Southern-Central Mediterranean Sea.

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.