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The physiological and ecological effects of temperature and oxygen on an estuarine fish

Beerkens, Nathan (2016) The physiological and ecological effects of temperature and oxygen on an estuarine fish. Honours thesis, Murdoch University.

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Temperature and oxygen are the primary abiotic variables controlling and limiting the metabolic capacity of fishes. This has been attributed to the strong influence of each variable on aerobic scope; the capacity of organisms to distribute energy across physiological functions. This study incorporates laboratory quantification of aerobic scope with field acoustic accelerometry to determine the relative importance of both temperature and oxygen to an estuarine teleost, the black bream (Acanthopagrus butcheri). In respirometry experiments, A. butcheri were found to display remarkably high thermal tolerance, maintaining stable aerobic scope across a 9°C thermal window. However, their aerobic scope was heavily reduced with reductions in oxygen availability, reaching a critical oxygen level at ~30% DO. The ecological importance of this was quantified in wild fishes as, whilst temperature displayed little effect on movement dynamics, the presence of hypoxia resulted in significant habitat compression, with bream restricted to shallow, oxygenated microhabitats. Under such compression, bream are likely to be at increased risk of predation and the negative effects of increased density, including competition and disease. These results provide empirical evidence for the hypothesis that hypoxia is a key driver of A. butcheri growth rates within the Swan River Estuary. It also highlights the population’s vulnerability to hypoxic episodes, which are expected to increase in both extent and frequency as a result of anthropogenically-enhanced eutrophication and climate change.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Supervisor(s): Gleiss, Adrian and Beatty, Stephen
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