Movement, habitat utilisation and population status of the endangered Maugean skate and implications for fishing and aquaculture operations in Macquarie Harbour

BELL, J.; LYLE, J.; SEMMENS, J.; AWRUCH C. A.; MORENO, C.; CURRIE, S.; MORASH, A.; ROOS, J.; BARRET, N.

2013-02-01/2015-02-01

1-84

Biológica

Otros campos

Executive SummaryThe present study, undertaken by the Institute for Marine and Antarctic Studies, represents the firstmajor investigation of the ecology and biology of the endangered Maugean Skate (Zearajamaugeana). Maugean Skate are only known from two estuarine systems located on the west coast ofTasmania (Macquarie Harbour and Bathurst Harbour), suggesting that the species has one of mostrestricted distributions of any elasmobranch.The Maugean Skate is afforded a degree of protection in the World Heritage listed Bathurst Harbour, ano-take marine protected area, although they appear to be rare in this location. In Macquarie Harbourthey appear to be relatively abundant but are subjected to multiple impacts due to human activities:they are a by-catch in recreational gillnets, and salmonid aquaculture operations are widespread andexpanding in Macquarie Harbour. It is not known how these activities, coupled with theenvironmental variability in Macquarie Harbour, impact on the Maugean Skate population.ObjectivesDue to the issues outlined above, the present study aimed to:1. determine the distribution, habitat utilisation and movement of the Maugean Skate inMacquarie Harbour;2. determine the key biological characteristics of Maugean Skate, including population size,reproductive dynamics and feeding habits;3. describe the spatial and temporal dispersal patterns of aquaculture escapees;4. assess the potential impacts of current and proposed marine farming operations on theMaugean Skate population; and5. evaluate strategies to reduce the probability of encountering Maugean Skate whilst fishing(gillnetting) for escapeesMethodologyTo address the above objectives, an extensive array of acoustic receivers was placed throughoutMacquarie Harbour. This array comprised several curtains to assess harbour wide movements, alongwith a high density of receivers amongst the marine farms and in areas where Maugean Skate areabundant and recreational gillnetting is common. A total of 58 Maugean Skate were acousticallytagged at multiple locations in the harbour and, to simulate a salmonid escape event, 30 AtlanticSalmon and 30 Rainbow Trout were acoustically tagged and released. To address the remainingobjectives, seasonal biological sampling was conducted over a period of 15 months. Reproductivestatus was assessed using non-destructive techniques (endocrinology and ultrasonography) andstomach lavage was used to investigate diet. A preliminary assessment of metabolic response tovarying levels of dissolved oxygen was also undertaken experimentally. All skate were PIT taggedprior to release and population size estimated using tag recapture rates throughout the study period.