Impact of water development on river flows and the catch of a commercial marine fishery

Andrew Broadley,Ben Stewart‐Koster,Rob A Kenyon,Christopher J Brown,Michele A Burford

doi:10.1002/ecs2.3194

Andrew Broadley, Ben Stewart‐Koster + Show 3 more

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https://doi.org/10.1002/ecs2.3194

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Journal: Ecosphere	Publication Date: Jul 1, 2020
Citations: 13	License type: CC BY 4.0

Affiliation: Griffith University, CSIRO Oceans and Atmosphere

Abstract

AbstractThe growing demand for freshwater resources has led to dam construction and water diversions in a majority of the world's large rivers. With an increasing demand for freshwater, trade‐offs between water allocations and the preservation of ecological connections between terrestrial and marine ecosystems are inevitable. The ecological links formed by rivers flowing into the ocean benefit many commercially fished species. The degree to which different species and the livelihoods of fishers are negatively impacted by changes in river flows due to water extraction or diversion is important for management across terrestrial and marine boundaries. Our objective was to predict how changes in freshwater flows from three wet–dry tropical rivers in northern Australia, that is, the Mitchell, Gilbert, and Flinders rivers, affect the commercial banana prawn (Penaeus merguiensis) catch. We used a novel spatiotemporal Bayesian approach to model the effects of river flows and key climate drivers on banana prawn catch. We then predicted how the loss of flow due to water extraction or diversion affected prawn catch. Our analyses of three water development scenarios found that catch was most impacted by water extraction during low flows. The impact of water extraction was greatest for a scenario with dams on the Mitchell River, where we predicted catch would decline by 53% during a year with low flow. Overall, our results imply that maintenance of low‐level flows is a crucial requirement for sustained fishery yields. We suggest that water managers must balance agricultural demand for water during drier years against the impact of water extraction on prawn fisheries during low‐flow years. Protecting low‐level flows during drier years is a priority for maintaining terrestrial–marine linkages for adjacent marine fisheries.

Highlights

The connections between terrestrial and marine ecosystems are a critical interface for ecological dynamics and have important implications for fishery management (Hughes et al 2015, Brown et al 2019)
Study area Situated in northern Australia, the Gulf of Carpentaria is a large semi-enclosed body of water covering an area of approximately 400,000 km2 (Fig. 1)
Our results show that managing equitable water extraction during periods of extended low flows or drought conditions, like those seen in the region from 1985 to 1990, will be challenging for sustaining fishery yields

Summary

Introduction

The connections between terrestrial and marine ecosystems are a critical interface for ecological dynamics and have important implications for fishery management (Hughes et al 2015, Brown et al 2019). It is often difficult to distinguish between human and natural sources of variability in coastal ecosystems, because of the confounding nature of environmental change on ecological processes (Brown et al 2019). Despite these difficulties, there is mounting evidence that accounting for changes in the environment may improve fish stock predictability and contribute to better management of commercial fisheries (Szuwalski et al 2015)

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