Reservoir to river: Quantifying fine-scale fish movements after translocation

Translocation of individuals is a widely used tool in the conservation of threatened species. The movement behaviours of translocated individuals in their new environment are a key factor that can influence translocation success (i.e. survival and reproduction). In this study, eel-tailed catfish (Tandanus tandanus) and Murray cod (Maccullochella peelii) movements were monitored using fine-scale acoustic telemetry over a 5-month period in two lowland rivers in eastern Australia. Fine-scale movement and habitat selection were compared among translocated lacustrine and resident riverine T. tandanus and between species. We found no difference in fine-scale movement behaviours between translocated and resident T. tandanus; however, there was some variation in movement response to environmental variation between species. In contrast, habitat selection varied not only between the two species, but also between resident and translocated T. tandanus individuals. Notably, activity was significantly lower in the first day after release compared to the remainder of the study period. Although T. tandanus translocated from a reservoir had never experienced the environmental fluctuations of a riverine system, individuals still responded in the same way as resident riverine fish, suggesting an innate behavioural response. However, this was not the case for habitat selection, where translocated individuals preferred habitats more common in their source population's lacustrine environment. The findings of this study are important in guiding future conservation efforts involving the translocation of wild-caught fish, primarily the importance of the suitable habitat at the release site to ensure the success and persistence of translocated populations.