Response of estuarine fishes to elevated temperatures within temperate Australia: Implications of climate change on fish growth and foraging performance

摘要

Range shifts of marine fishes are well documented to respond to climate change, however the physiological mechanisms linked to these shifts are poorly understood. Responses of estuarine fishes, which have limited scope to shift, are particularly lacking. We tested the influence of present (18 degrees C, 22 degrees C) and predicted near-future (26 degrees C) water temperature on the growth and foraging performance of five common co-occurring fish: eastern trumpeter Pelates sexlineatus (Quoy & Gaimard 1824), eastern fortescue Centropogon australis (White 1790), yellowfin bream Acanthopagrus australis (Owen, 1853), fan-belly leatherjacket Monacanthus chinensis (Isbeck 1765), bridled leatherjacket Acanthaluteres spilomelanurus (Quoy & Gaimard 1824), from an urbanised, temperate estuary near Sydney. Growth performance was quantified as instantaneous growth rate over a two-week period, whilst foraging performance was assessed on bite rate, time to feeding, boldness and also escape response. Growth patterns were significantly species-specific, and all species except for M. chinensis (high within-treatment variance) exhibited significant growth differences among the temperature treatments. The growth of P. sexlineatus and A. australis increased with temperature, A. spilomelanurus lost weight with temperature and C. australis exhibited a hump-shaped performance curve with the highest growth occurring at 22 degrees C. Bite rate, boldness, and escape response increased, and time to feeding decreased with higher water temperature in P. sexlineatus, A. australis and M. chinensis. Surprisingly, there was no significant association between these foraging characteristics and growth rate of individuals within each temperature treatment. This study validates the hypothesis that species within temperate estuaries will be significantly, and differently, affected by the isolated impact of water temperature rise, culminating in changes in local fish assemblages. These changes may include shifts in species dominance, trophic interactions, and migration, as well as changes to the productivity of fisheries that rely on these populations.