Using abiotic drivers of fish spawning to inform environmental flow management
Abstract
- Environmental flows are a key restoration technique for conserving ecological function in flow-degraded rivers. Species-specific, flow–biota relationships are increasingly being used to determine environmental flow needs and manage their use; however, many of these relationships are poorly described.
- We evaluate relationships between environmental variables and spawning intensity for a fish assemblage from the Murray River, Australia, over a ten-year period. We developed a hierarchical multispecies model that accounted for incomplete detection to compare spawning outcomes of native and non-native species using realistic, alternative, water management scenarios.
- Temperature was an important predictor of spawning intensity for all seven species studied, while both concurrent and antecedent flow conditions were important for many species. Our water management scenario testing accounted for these relationships and indicated that increasing the magnitude of smaller floods following lower antecedent flow conditions, at water temperatures of 18–20°C, achieves the greatest spawning outcome for native fish.
- Synthesis and applications. Our results indicate that principally temperature, and flow as a secondary variable, influence the timing and strength of fish spawning. The synthesis of these spawning relationships predicts that managers will achieve the greatest spawning return per unit of environmental water when flows are applied on top of an existing flow pulse. This study highlights the importance of considering a range of abiotic factors and the use of modelling scenarios to improve environmental flow outcomes.