Reproductive strategy of the Australian Sharpnose Shark, Rhizoprionodon taylori (Elasmobranchii: Carcharhinidae), from Cleveland Bay, Northern Queensland

Abstract

Reproduction and early embryo development of Rhizoprionodon taylori from Cleveland Bay, Queensland, was studied on the basis of 455 specimens caught between May 1987 and February 1990. Males and females mature at sizes larger than those reported from northern Western Australia, the Northern Territory and far northern Queensland. Mating occurs annually in summer, and the gestation period is approximately 11.5 months. After development to a small blastodermic disc, the embryos enter a state of diapause that lasts approximately 7 months. R. taylori is the only species of shark that is known to have a period of embryonic diapause. The litter size ranges from 1 to 10 (mean 4.9, being markedly larger than that for other carcharhinid species of a similar size. The size at birth is 220- 260 mm. The reproductive and developmental traits are discussed in relation to the life histories of this species and other carcharhinids.