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Abstract
Freshwater flow profoundly influences fisheries production in estuarine and coastal systems. Although connections between freshwater flow and fisheries production are well established, underlying mechanisms remain poorly understood. Investigating relationships between freshwater flow and fisheries production is essential to ensure that the interests of commercial fishers are represented in debates over environmental flows. This thesis examines the impacts of freshwater flow on the production and profitability of estuarine and coastal fisheries. Chapter 1 outlines relationships between freshwater flow and fisheries production in estuarine and coastal systems. Chapter 2 presents a literature review which indicates that freshwater flow influences fisheries production by regulating habitat availability, trophic interactions and fishers’ harvesting behaviour. Chapter 3 examines relationships between hydrological variation and the commercial catch rates of five estuarine-associated fish species from nine estuaries in New South Wales (NSW), eastern Australia. Freshwater enhancement of fisheries production was evident, with increased catch rates in months with higher flow. Freshwater flow per se, however, was not as important in influencing catch rates as episodic flow events. Chapter 4 explores the impacts of episodic flow events on estuarine and coastal fisheries by examining multivariate patterns in landings, effort and revenue between periods of flood and drought. Results indicate that flood and drought events influence the bio-economic productivity of commercial fisheries by modifying landings composition, fishers’ harvesting behaviour and revenue generation. Chapter 5 presents a multi-species, multi-method bio-economic analysis that was used to evaluate the economic performance of fishers’ harvesting strategies between non-drought and drought conditions. Projections from the model indicate that droughts redistribute revenue and profit among fishing methods, modifying the economic performance of commercial fisheries. Although diversified harvesting behaviour increased revenue generation, this marginal economic benefit was compromised by higher costs which lowered profitability. Results indicate that the commercial fishing sector is a drought-affected industry in coastal NSW. Chapter 6 summarises the findings of the research presented in this thesis and suggests directions for future work. The research described here provides empirical evidence that freshwater flow regulates the availability of fisheries resources, fishers’ harvesting behaviour and the economic performance of commercial fisheries in estuarine and coastal systems.