Dietary analysis reveals the vulnerability of the endangered Maugean skate (Zearaja maugeana) to benthic changes in Macquarie Harbour
Kay Weltz
A B , Jeremy M. Lyle A , Justin D. Bell A and Jayson M. Semmens A
+ Author Affiliations
- Author Affiliations
A Institute for Marine and Antarctic Studies (IMAS), University of Tasmania, 15-21 Nubeena Crescent, Taroona, Tas. 7053, Australia
B Corresponding author. Email: weltzkza@gmail.com
Marine and Freshwater Research 70(5) 745-753 https://doi.org/10.1071/MF18231
Submitted: 26 June 2018 Accepted: 29 October 2018 Published: 21 December 2018
Abstract
Species occupying high trophic positions with a small population size, limited diet and restricted range are vulnerable to extinction. The endangered Maugean skate (Zearaja maugeana) in Macquarie Harbour is potentially threatened by changing benthic environmental conditions (declining dissolved oxygen concentrations and decreased macrofaunal diversity). To inform investigations on potential indirect impacts of benthic environmental changes on the Maugean skate and its prey, non-lethal techniques were used to identify dietary composition and trophic position of the species. The Maugean skate occupies a high trophic position (3.70) in the food web, with both stable-isotope (median 86% contribution to isotopic signatures, credible interval (CI) = 44–100%) and stomach-content analysis showing crustaceans, particularly brachyuran crabs (58.5% index of relative importance), as the dominant prey type. Aquaculture feed from salmonid fish farms operating in the harbour was not found to be important in skate diet. This study showed that the Maugean skate consumes a small number of benthic prey species, highlighting its vulnerability to changing environmental conditions in the harbour.
Additional keywords : endangered elasmobranch, stable isotope mixing model, stomach-content analysis, trophic position.
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