Movement and behaviour of the endangered Maugean skate, Zearaja maugeana, in Macquarie Harbour, Tasmania

Maugean skate (Zearaja maugeana) are a micro-endemic solely inhabiting two embayment’s in western Tasmania. The population in Bathurst Harbour appears to be small and although the Macquarie Harbour is relatively large it is subject to anthropogenic pressures including pollution from historic mining, salmonid aquaculture and gillnetting. As such, the present study investigated the spatial utilisation of Maugean skate in Macquarie Harbour to determine how the above pressures are likely to impact the population and formulate strategies to minimise them. Maugean skate are highly philopatric with 50% (core range) and 95% (home range) utilisation distributions generally <3km2 and <10km2 respectively. The core range of only one skate overlapped with aquaculture leases, whereas the home range of most individuals did overlap but by <2km2 in all cases. Maugean skate displayed an affinity for waters 6–12m deep, which is likely dictated by water chemistry: shallow waters have low salinity and high temperature variability; deep waters are stable but have low dissolved oxygen; waters 6–12m deep are relatively stable. They also displayed diurnal variation in depth utilisation, presumably representing foraging behaviour. Direct interactions between Maugean skate and aquaculture operations were minimal. There may, however, be indirect interactions whereby organic wastes and reduce dissolved oxygen or increase dissolved nutrients. A number of changes were implemented to reduce impacts of gillnetting on Maugean skate as a result of this study; spatial closures limiting gillnetting mainly to waters <5m and the closure of areas important to the species are anticipated to greatly reduce captures.