Understanding movement and habitat-use to guide reintroductions and habitat rehabilitation for a nonmigratory freshwater fish

Outcomes from restoration and reintroduction programs can be enhanced by understanding the habitat use of animals, and how likely they are to move and why? River blackfish are native to southeastern Australia where their range and abundance have declined. We reintroduced 27 river blackfish into two sites, one where rehabilitation had been undertaken (with more vegetation, instream woody habitat, and undercut banks) and an unmanipulated control site. We monitored fish for 9 months after release to assess site occupancy, habitat use, and drivers of movement. We modeled the likelihood of fish remaining at either site, their habitat use, and predictors of movement (site type, habitat, time, and river discharge). While more fish remained at the treatment site, this difference was not statistically significant. Future trials incorporating increased numbers of fish and replicate treatment and control release sites would allow a more detailed test of whether fish are more likely to remain at restored sites. Fish spent more time in deeper areas with more riparian vegetation. Habitat, flow, and time since release were significant predictors of fish movement, with fish more likely to move from release sites with less suitable habitat, during rainfall events, and during the initial stages of our study. Our results illustrate that blackfish are a suitable candidate for translocations, retaining their largely sedentary behavior and should be easily measurable if restoration has provided suitable habitat and their presence is an indicator of success. Our work is also a useful case study for translocation of other nonmigratory fish worldwide.