River flows affect the growth of a tropical finfish in the wet-dry rivers of northern Australia, with implications for water resource development

Abstract

Freshwater is a critical input to estuaries but is under increasing demand to support upstream human activities. In this study, otolith biochronology was used to quantify the relationship between river discharge and juvenile growth rates of barramundi (Lates calcarifer) in three regions of the Gulf of Carpentaria in northern Australia. In all regions, river discharge had a strong positive effect on juvenile growth rates. Models were also developed which incorporated the Southern Oscillation Index (SOI) and the Madden-Julian Oscillation (MJO). SOI values corresponding to La Niña events had strong positive consequences for juvenile barramundi growth rates in all regions, and the intensity of positive wet season MJO pulses had a strong positive effect on growth rates in the perennially flowing river, but not the intermittently flowing rivers. The consequences of three hypothetical water development scenarios were estimated for the perennial river. The model predicted a 12%, 8% and 1% reduction in annual barramundi growth rates under proposed scenarios for 18%, 8%, and 3% reduction in river discharge, respectively. Fish growth is a robust, quantitative metric that can be monitored pre and post water resource development to identify the least impactful development scenario and monitor its compliance and success through time.

Modelling the longitudinal distribution, abundance, and habitat use of the giant freshwater shrimp (Macrobrachium spinipes) in a large intermittent, tropical Australian river to inform water resource policy

“…Relationships between interannual flow magnitude and recruitment of amphidromous shrimps have been proposed in the literature (Novak, Garcia, Pusey, & Douglas, 2017) but have rarely been quantified. However, positive flow‐recruitment relationships have been documented for other diadromous species in northern Australian, including Barramundi (Crook et al, 2022; Leahy & Robins, 2021) and sawfish (Lear et al, 2019). In tropical northern Australia, larger wet season flows are thought to promote cherabin recruitment by increasing the number of larvae drifting down to the estuary.…”

Ecosystem services in connected catchment to coast ecosystems: monitoring to detect emerging trends

“…For comparison, proposed water developments in the Mitchell catchment are expected to cause much smaller reductions in flow, in order of 1-5% per year (Petheram et al 2018), than most of the trends we explored here. Such water developments however are predicted to impact estuarine ecosystem services (Broadley et al 2020;Leahy & Robins 2021). Thus, our findings suggest management planning will have to rely heavily on predictive modelling, and should not be guided in the shortterm by trends in condition accounts.…”

“…Individuals residing in upstream habitats to the estuary and saltwater, to eventually participate in spawning as adults. Barramundi are impacted by the flow regimes through changes in connectivity throughout the catchment, which benefit growth and survival (Robins et al 2005;Balston 2009;Roberts et al 2019;Leahy & Robins 2021). Barramundi opportunistically exploit multiple ecosystem assets (i.e., aquatic habitats) at different stages of their life cycle.…”

Environmental drivers of recruitment in a tropical fishery: Monsoonal effects and vulnerability to water abstraction

“…The difficulties of applying complex, correlative environmental relationships to the management of Barramundi are emblematic of many other near‐shore coastal, estuarine, and riverine fisheries around the world (Dolbeth et al, 2011; Rytwinski et al, 2020). Therefore, there is a need for integrated approaches that capture the most salient climatic/hydrologic drivers of fishery productivity in forms that can be readily applied to fisheries and water resource management (Leahy & Robins, 2021; Maunder & Punt, 2013; Morrongiello et al, 2014; Robins et al, 2005).…”