Pease B and Green B (2007) Observing fish behaviour at tidal floodgates. Oral presentation given at the 16th NSW Coastal Conference, 7–9 November 2007, Yamba, NSW, Australia.

Conference paper also available on-line at: http://www.coastalconference.com/2007/default.asp.

Summary

Coastal floodplains provide essential nursery, feeding and spawning habitats for a wide range of fish species. In NSW, an extensive system of floodgates has been installed in many of these floodplain areas and recent studies by the New South Wales Department of Primary Industries (NSW DPI) have shown that unmanaged floodgates act as barriers to fish. Programs of active and passive floodgate management are now being widely implemented. In order to maximize access to wetlands through adaptive management of floodgates, information is needed about the variability of fish passage over time and physical factors that may restrict this access. However, direct observation of fish behaviour is made difficult by the generally poor water visibility near floodgates.

The NSW DPI has recently purchased an underwater acoustic camera, known as a Dual Identification Sonar or DIDSON, which enables us to observe and record videos of fish in highly turbid water and at night. We have been conducting trials to determine the initial protocols for programming and placement of a DIDSON acoustic camera in order to capture and quantify fish movement behaviour above and below modified floodgate structures, rock ramps, fish ways and weirs. Analysis of the video footage is not complete, however we have some interesting preliminary observations of fish passing through tidal floodgates and aggregations of fish above and below floodgate structures. In this paper we summarise our observations of fish aggregation and movement patterns and discuss some implications for active and passive management of tidal floodgates.