Divergent use of a south-western Australian estuary by four key recreational fish species: evidence from acoustic telemetry

By examining fish movements in estuaries we can gain a better understanding of how fish respond to environmental changes in these highly dynamic environments, compare how co-occurring species use estuarine systems, and determine areas where populations may be most vulnerable to fishing pressures. In this study, four important fishery species; Black Bream (Acanthopagrus butcheri), Southern Bluespotted Flathead (Platycephalus speculator), Snapper (Chrysophrys auratus) and Tarwhine (Rhabdosargus sarba), are being tracked using acoustic telemetry in the permanently open Walpole-Nornalup Estuary, a popular recreational fishery on the south coast of Western Australia. A fixed array of 17 Vemco VR2W acoustic receivers has been deployed to track the movements of fish surgically implanted with internal acoustic transmitters. 23 Black Bream, 16 Southern Bluespotted Flathead, 10 Snapper and 10 Tarwhine have been implanted with transmitters (Vemco V8 or V9 -dependent on body size). Preliminary analyses of acoustic telemetry data reveals marked differences in movement patterns, habitat preferences and spatial area use of the system among species. Likewise, key environmental and biological factors, including salinity, water temperature, tidal phase, reproduction and body size, have varying effects on the movements of the four study species. For managers, this information can enhance existing knowledge of how fish use south-western Australian estuaries, particularly the degree of connectivity between regions and populations, potential habitat overlap between species, and how fish populations may respond in varying ways to a changing climate and increasing anthropogenic pressures.