Advances in Fish Tagging and Marking Technology

Abstract

<i>Abstract</i>.—Movement patterns of two co-occurring catadromous fishes, estuary perch <i>Macquaria colonorum </i>and Australian bass <i>Macquaria novemaculeata</i>, were investigated in a large tidal river in southeastern Australia. Nineteen estuary perch and seventeen Australian bass were captured as mature adults from the Shoalhaven River, surgically implanted with electronic transmitters and released. Forty-nine Vemco (VR2W) acoustic receivers were strategically placed throughout the river from the Tallowa Dam wall downstream to the sea (a distance of 75 km). Between September 2007 and February 2008, a total of 800,263 detection events were recorded with most fish detected in the middle (estuary perch) to upper (Australian bass) estuarine reaches of the river. Both species made extensive use of the estuary, with no estuary perch and only three Australian bass entering the freshwater, indicating that the freshwater residency phase of these catadromous fishes may not be obligatory. The data also suggests that estuary perch and Australian bass exhibit high site fidelity, which, along with their large scale movements may be influenced by factors such as river discharge and prey availability. This large freshwater-estuarine telemetry array combined with critical abiotic information (river discharge and salinity) has and will provide a greater understanding of catadromous fish movement, particularly in relation to habitat utilization and environmental flows.