Managing environmental flows in the Murray-Darling Basin for fish recruitment is currently limited by knowledge regarding the relative importance of individual drivers; interactions among drivers, flow and non-flow related stressors; and how these relationships vary among species. Three intensive reviews were undertaken pertaining to fish recruitment: (a) an assessment of non-flow drivers, (b) a review of current knowledge and management needs in the MDB and (c) theoretical review and conceptual model development using the literature.
A key outcome from the conceptual model development showed that fish recruitment is determined by the spatial and temporal coincidence of early life stages (movement and retention) with optimal conditions (high food, low predation, optimal temperature). Based on this and key elements of the review activities, a research plan was developed that addressed three key questions:
Our research demonstrates that fish population processes and the drivers that support recruitment, operate at multiple spatial scales, from patch to the river basin. Important drivers of recruitment were the coincidence of areas of food production areas coupled with appropriate temperature regimes, and the ability for larval dispersal or retention at patch to segment scale. For riverine fishes, hydraulic diversity is integral to providing appropriate conditions for food production and dispersal/retention of early-life stages. Connectivity is critical in enabling access to appropriate habits and dispersal to maintain populations at catchment to basin scales. Our research also demonstrated that under drought conditions, factors such as abundance and condition of adults, and maintenance of refuge areas are also playing a critical role in determining recruitment success.