Not so sessile: A first multi-month telemetry study reveals fine-scale movement and space use in translocated Obovaria olivaria

Translocation is widely used to mitigate impacts on threatened freshwater mussels, yet post-release behaviour remains poorly understood because conventional monitoring provides limited temporal resolution. Here, we used fine-scale acoustic telemetry to quantify movement and space use of the endangered freshwater mussel Obovaria olivaria following relocation in the St. Lawrence River (Canada). Near-complete detection success was achieved, with 35 out of 36 tagged individuals successfully tracked over a ∼ 120-day period, demonstrating the feasibility of this approach in a highly turbid and dynamic large river system. Median daily displacement (5.9 m day⁻ 1 ) slightly exceeded residual positioning noise (<4.4 m day⁻ 1 ) while remaining confined to very small activity areas (<10 m 2 ), indicating continuous but spatially constrained movement. Because cumulative displacement is sensitive to system noise, spatial patterns were interpreted using centroid-based metrics, which revealed strong spatial confinement and stability over time. Spatial behaviour was characterized by high variability during the first ∼ 2 weeks after release, followed by greater stability and spatial fidelity, although seasonal effects cannot be separated from post-translocation adjustment without an undisturbed control group. A moderate increase in space use in October further suggests that seasonal processes contributed to the observed temporal pattern. These results provide the first quantitative benchmarks of post-translocation movement in this species and show that automated acoustic telemetry can provide a complementary behavioural indicator for post-translocation assessment. Future multi-year monitoring integrating survival, growth, physiological condition, and environmental data will help identify drivers of movement and improve conservation strategies.