The reproductive biology and ecology of the Port Jackson shark Heterodontus portusjacksoni in the coastal waters of eastern Australia

Abstract

The reproductive biology and ecology of the Port Jackson shark Heterodontus portusjacksoni was investigated at three locations on the central and southern coast of New South Wales (NSW), Australia from January 2002 to December 2005 using underwater visual census surveys and samples obtained from a commercial fishery. Adults displayed sexual dimorphism in total length (LT) at sexual maturity, with males maturing between 762 and 772 mm LT and females between 902 and 905 mm LT. The mean ovarian fecundity was estimated at 16 offspring per female but was unrelated to female LT. Male gonado‐somatic (IG) and hepato‐somatic (IH) indices and female IG declined from July to November as did maximum ovarian follicle diameter and the diameter of the three largest follicles. Adults were absent from inshore reefs between December and July. Hence, H. portusjacksoni has a synchronous annual breeding season in NSW, which occurs between July and November (the austral winter to spring), with a peak in oviposition from August to October. Heterodontus portusjacksoni copulatory and ovipository behaviour are reported for the first time. Copulation was observed and involved oral grasping of the female’s pectoral fin by a single male, which wrapped his body around hers to insert one clasper. Ovipositing females appeared to search crevices in the reef prior to delivering a single capsule, which was washed into the crevice by water movement, with the female departing very soon after oviposition. This study represents the first rigorously quantitative analysis of H. portusjacksoni reproductive biology and ecology in NSW waters.