Impacts of drought and predicted effects of climate change on fish growth in temperate Australian lakes

Abstract

Climate change is expected to negatively impact many freshwater environments due to reductions in stream‐flow and increases in temperature. These conditions, however, can already be found today in areas experiencing significant drought; current observations of species' responses to droughts can be used to make predictions about their future responses to climate change. Using otolith analysis, we recreated golden perch (Macquaria ambigua) growth chronologies from two temperate lake populations in southeastern Australia over a 15‐year period pre‐ and during a supraseasonal drought. We related interannual growth variation to landscape‐scale changes in temperature and hydrological regimes: fish growth declined as water levels in the lakes dropped during the drought, but this effect was offset by increased growth in warmer years. We hypothesize that golden perch are responding to fluctuations in food availability and intraspecific competition related to water level and to an optimization of physiological growth conditions related to increases in growing season length. Based on our analyses, we made predictions of future growth under a number of climate change scenarios that incorporate forecast deviations in stream‐flows and air temperature. Despite climatic models predicting significant declines in future water availability, fish growth may increase due to a disproportionate lengthening of the growing season. As the two lakes are at the limit of the southerly range of golden perch, our results are consistent with previous findings of climate‐change driven latitudinal range shifts in a poleward direction. We discuss assumptions concerning the constancy of ecological interactions into the future that warrant further study. Our research provides a novel application of biochronological analysis that could be used elsewhere to further our knowledge of species responses to changing environments.

Climate change and its implications for Australia's freshwater fish

“…For example, the southerly range of golden perch (M. ambigua) is partly temperature-limited. Morrongiello et al (2011) found that during the recent drought, the annual growth of M. ambigua in south-eastern Australian lakes was negatively correlated with declining water levels; however, this effect was offset by increased growth during warmer years. Despite climatic models projecting significant declines in future water availability, fish growth may increase because of a disproportionate lengthening of the growing season, and thus make these higher latitudes more favourable habitat.…”

Detecting range shifts among Australian fishes in response to climate change

“…The effects of temperature on growth rates may also have indirect impacts by altering reproductive output and competitive interactions (e.g. Morrongiello et al 2011).…”

“…Climate-change drivers such as temperature and rainfall can operate directly to affect range or indirectly through effects on habitat or food resources of fishes (e.g. Morrongiello et al 2011;Pratchett et al 2011) or on their reproduction (Pankhurst and Munday 2011). Climatechange drivers can also interact with other factors such as overfishing, habitat removal, disease and pollution to reduce or spatially shift species.…”

Influence of Basin‐ and Local‐Scale Environmental Conditions on Nearshore Production in the Northeast Pacific Ocean

“…All models included the age at increment formation to account for the faster growth of younger fish (Morrongiello et al 2011). Annual otolith increment widths and ages were log transformed prior to analysis to achieve homoscedasticity and a linear relationship between these two variables.…”