Freshwater catfish, Tandanus bostocki, move further and maintain larger home ranges during elevated flow in a regulated river, Western Australia

Movement and migration of fish can be important to the completion of life cycles and the persistence of meta-populations. However, fish movement can be impacted by river regulation if it disconnects habitats and removes the hydrological cues required. Managed water releases, i.e., environmental flows, can be used as a restoration tool; however, their efficacious design and implementation requires a robust understanding of flow-ecology relationships. In this study we used radio telemetry to investigate whether river discharge influenced the movement of Tandanus bostocki, a plotisid fish endemic to south-western Australia and impacted by regulated river flows. Movement was assessed for 15 adult fish (males, females) at three temporal scales: bihourly, daily around a flow pulse and weekly. Movement of T. bostocki was strongly associated with elevated river flows, with fish moving downstream once flow exceeded 50 Ml/d, although the average distance travelled was relatively modest (< 800 m). While fish maintained larger home ranges during seasonally elevated baseflow, the linear distance moved by individuals per unit time did not vary with baseflow magnitude. We constructed flow-movement models that support a link between flow and movement of T. bostocki. The study highlights the importance of managing base-flow, and the magnitude, duration and recession rate of elevated flow events, to facilitate both localised and larger scale movements in regulated rivers.