Deficiencies in our understanding of the hydro-ecology of several native Australian fish: a rapid evidence synthesis

Abstract

Environmental flows aim to mitigate the impacts of modification of riverine flow regimes by restoring components of the natural flow regime. Explicit evidence-based cause–effect relationships between flow regimes and fish responses are required for defensible flow recommendations. However, flow recommendations are typically based on expert opinion rather than a rigorous test of the available evidence. We used rapid evidence synthesis to systematically review the literature on responses of several native Australian fish to flow-related and other important environmental variables, and tested 13 explicit hypotheses. The hypotheses were related to the condition, reproduction and survival of pygmy perches, carp gudgeons, blackfish and flat-headed gudgeons. The evidence was insufficient to reach strong conclusions for all but three of our hypotheses. Late-spring high flows are associated with increased survival of pygmy perches and carp gudgeons, and exotic fish are associated with decreased survival of these fishes. The evidence that warmer spring water temperatures enhance their reproduction was inconsistent. The dearth of evidence to support or refute most hypotheses points to substantial gaps in our understanding of hydro-ecology of these native Australian fish, highlighting the need for targeted monitoring and research to further understand key flow relationships for these fish species.