Life History and Underwater Studies of a Heterodont Shark
1971
McLaughlin, R. H. | O'Gower, A. K.
The biology of Australian reef populations of the shark Heterodontus portusjacksoni has been studied underwater with SCUBA. Additional life—history data have been obtained from catch records of adults and juveniles and from observations on captive animals. The mature breeding female H. portusjacksoni lays 10—16 eggs which are deposited in rock fissures on shallow reefs; the young emerge approximately 1 year later. The breeding season on the central coast of New South Wales occurs in late winter and spring. This species appears to segregate by sex into separate juvenile, adolescent, and adult populations. A slow growth rate and protracted immaturity is characteristic. Sexual maturity is reached at 8—10 years for males and 11—14 years for females. Most feeding occurs during darkness over both reefs and soft substrates, gut contents reveal that they feed on a variety of benthic invertebrates. Populations of H. portusjacksoni observed on sublittoral reefs consisted of adult sharks, the majority of which were females. A few specific sites, usually caves in which they shelter during the day, are preferred. Resightings of sharks tagged on a reef at Bondi, Sydney, revealed that animals which formed the local population moved freely to and from the reef and also between the several sites on the reef. Reef densities were highest during the breeding season and were correlated with low water temperatures. Emigration from inshore reefs occurs at the end of the breeding season in late September and October. A number of tagged sharks returned to the same reef in the following year and others after periods of up to 2 years. Recaptures made outside the Sydney area indicate that some sharks may travel several hundred kilometers during their migration.
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