Fish body condition and recruitment success reflect antecedent flows in an Australian dryland river

Abstract

In fluctuating aquatic environments such as intermittent streams, fish condition is often highly variable due to the associated fluctuating levels of food resources. Having the physiological capacity to both metabolise and catabolise lipids, fish can survive through droughts and rapidly gain condition during flows and floods. Dryland rivers continuously cycle through periods of boom and bust due to their intermittent patterns of rainfall and flow. To help gain an understanding of how fish respond physiologically to varying antecedent flow conditions, we examined body condition measured by percent tissue water content of two generalist fish species in an Australian dryland river. We predicted that fish would be in better condition following recent flows and poorer condition when there had been no recent flows. Our expectations were met for both species with low water tissue content after high flows and high tissue water content after significant drying. It was also found that strong juvenile recruitment was also evident when body condition was high, indicating that when there are food resource spikes driven by flow pulses fish can utilise resources both to produce offspring and to store as lipid for future survival.