Biology and ecology of Zearaja maugeana, an Endangered skate restricted to two south-western Tasmanian estuaries

Abstract

The Endangered Maugean skate Zearaja maugeana is a relic species restricted to two isolated estuaries, Bathurst Harbour and Macquarie Harbour, in south-western Tasmania, Australia. Over a 1-year period, dive, tagging and net surveys provided information on the biology and ecology of this species. In all, 96 Maugean skates were caught during five trips to Macquarie Harbour, with four additional individuals observed underwater; however, no animals were located in the single trip to Bathurst Harbour. Morphometrics and the sex of the animals were recorded for 95 individuals. Crustaceans dominated the diet, with the majority of animals feeding on the crab Paragrapus gaimardii. Recapture rates were very low, with only one of 82 pit-tagged skates recaptured, and that occurred on the day of release. One acoustically tagged male skate was tracked for 5km along the harbour margin for 24h, whereas a female skate tracked for 46.5h showed high site fidelity, suggesting that multiple factors potentially influence habitat utilisation. Although Macquarie Harbour represents the stronghold for this species, this estuary is also experiencing major environmental disturbance and change. Conservation management of this Endangered skate requires specific consideration of aquaculture, recreational fishing and mine drainage effects, as well as ongoing monitoring.