Diurnal and nocturnal movements of river blackfish (Gadopsis marmoratus) in a south-eastern Australian upland stream

We used radio-telemetry to investigate the movement patterns of river blackfish [Gadopsis marmoratus (Richardson)] in Armstrong Creek, south-eastern Australia between August and October 2005. Movements of 11 fish were monitored 2-3 times per week during daylight over 48 days and diel movements of six fish monitored hourly for three consecutive days and nights. Most river blackfish displayed little or no movement during the day and were confined to distinct positions in the stream. However, fish moved over significantly larger ranges and moved amongst mesohabitats at night, which would not have been detected using daylight tracking data only. River blackfish most often were located within pools, but they also commonly used riffle and run habitats. We also found that several fish used inundated riparian areas during a flood and two fish made rapid, large movements coinciding with the elevated flows. This study has revealed previously undocumented aspects of the movements and behaviour of river blackfish. The study has also shown the potential for different conclusions regarding the extent of movement by a species depending on the temporal scale and the timing of observations.