Estuary Stingray - Biology and Ecology

Biology and Ecology

Despite its reputation for preying voraciously on oysters and other farmed shellfish, the estuary stingray's diet in fact consists mainly of crustaceans and polychaete worms. In Moreton Bay, an important prey species is the soldier crab (Mictyris longicarpus). This ray has been observed entering mudflats with the rising tide to forage for food. Known parasites of the estuary stingray include the tapeworms Heterocotyle chin and Shirleyrhynchus aetobatidis, the nematode Echinocephalus overstreeti, and the monogeneans Empruthotrema dasyatidis and Neoentobdella cribbi.

Like other stingrays, the estuary stingray exhibits aplacental viviparity, with the developing embryos sustained initially by yolk and later by histotroph ("uterine milk") produced by the mother. Females probably produce offspring every year. Courtship, in which the male follows the female and bites her disc, has been observed at night in water approximately 80 cm (31 in) deep in Hays Inlet from July to October. The newborns measure around 11 cm (4.3 in) across and 35 cm (14 in) long. Young rays have been caught in the Nerang and Macleay Rivers and in Hays Inlet; such fresh or brackish environments may serve as nurseries. Males mature at around 41 cm (16 in) across and seven years of age, and females mature at around 63 cm (25 in) across and 13 years of age. This disparity in maturation size between the sexes is among the widest known for stingrays. The maximum lifespan is estimated to be 16 years for males and 23 years for females.