Responses of large-bodied native fish to flows in the mid-Murray River Background Monitoring a response The controlled management of water flows (river We investigated annual growth patterns of regulation) is a major threatening process to the fish species, including the nationally ecological sustainability and integrity of rivers endangered Trout cod, Murray cod and golden throughout the Murray-Darling Basin (MDB). To perch in both the regulated Murray River and address such threats, water delivery is unregulated Ovens River. This involved examining increasingly being planned to meet environmental growth bands on otoliths (ear bone of fish) to needs. There is evidence that aspects of flow reconstruct annual fish growth over a 23-year regimes are linked to important components of the period, encompassing times of major drought, life history of fish species, including their growth, flood and environmental water delivery. River flow spawning and recruitment. data was then used to analyse the importance of key aspects of the flow regime in governing the Key fish populations, with recreational and cultural growth of these fish species. We then compared values, are our results between regulated and unregulated often used as indicator or ‘flagship’ species for target setting and reporting on systems, and made projections of fish growth in outcomes of such environmental watering. Our the Murray River under a natural flow regime, and knowledge of how the various aspects of flow also under a regime with and without regimes affect the life history of fish species is environmental water delivery. incomplete however, particularly for long-lived species. This limits our ability to implement optimal environmental water delivery programs to enhance fish populations in the MDB. In 2013, a project commenced to examine long term fish monitoring data to investigate linkages between flow regimes in rivers and the growth, recruitment and population responses of fish. What were the findings Results indicated that several aspects of a rivers flow regime are important for large-bodied fish productivity in temperate floodplain rivers. Growth of all three fish species in the Murray River was Environmental water delivery helps native fish species greater in years when flow was higher and more variable, particularly in spring, summer and
Background Responses of large-bodied native fish to flows in the mid-Murray River The controlled management of water flows (river regulation) is a major threatening process to the ecological sustainability and integrity of rivers throughout the Murray-Darling Basin (MDB). To address such threats, water delivery is increasingly being planned to meet environmental needs. There is evidence that aspects of flow regimes are linked to important components of the life history of fish species, including their growth, spawning and recruitment. Key fish populations, with recreational and cultural values, are often used as indicator or ‘flagship’ species for target setting and reporting on outcomes of such environmental watering. Our knowledge of how the various aspects of flow regimes affect the life history of fish species is incomplete however, particularly for long-lived species. This limits our ability to implement optimal environmental water delivery programs to enhance fish populations in the MDB. In 2013, a project commenced to examine long term fish monitoring data to investigate linkages between flow regimes in rivers and the growth, recruitment and population responses of fish. Environmental water delivery helps native fish species Monitoring a response We investigated annual growth patterns of fish species, including the nationally endangered Trout cod, Murray cod and golden perch in both the regulated Murray River and unregulated Ovens River. This involved examining growth bands on otoliths (ear bone of fish) to reconstruct annual fish growth over a 23-year period, encompassing times of major drought, flood and environmental water delivery. River flow data was then used to analyse the importance of key aspects of the flow regime in governing the growth of these fish species. We then compared our results between regulated and unregulated systems, and made projections of fish growth in the Murray River under a natural flow regime, and also under a regime with and without environmental water delivery. What were the findings Results indicated that several aspects of a rivers flow regime are important for large-bodied fish productivity in temperate floodplain rivers. Growth of all three fish species in the Murray River was greater in years when flow was higher and more variable, particularly in spring, summer and
fish-growth-response-to-flows-mid-Murray-fact-sheet-2015.docx