Movement to breed, disperse, and colonise new habitats is critical for most organisms. Flow stimulates movement of some aquatic species, presumably to breed and access new habitats. Freshwater turtles obtain high biomass and are important omnivores in freshwater systems, yet their movement patterns, and the influence of flow, remains a key knowledge gap.
To investigate turtle movement, and any influence of flow, we tagged 17 adult Emydura macquarii (7F : 10M) and 10 adult Chelodina expansa (6F : 4M) with 69 kHz acoustic transmitters in the regulated Gwydir River and the lowland Gingham Watercourse, NSW. An acoustic array spanning more than 100 km of river channel and consisting of 25 VR2W-69 kHz receivers was established to passively monitor their movements.
Ten of the 27 turtles moved at least 4 km on both high and low flows. Emydura macquarii were more likely to move, with only one female C. expansa moving away from the original site of capture. One male E. macquarii moved upstream through more than 70 km of river channel during multiple high flow events and lower flows. The female C. expansa passed through regulating structures and travelled across floodplains to parallel river channels during high flow events.
These preliminary results suggest that a proportion of the population of these two species is likely to move throughout a river system on both high and low flows. We show, for the first time, that E. macquarii can and will move large distances rapidly, whilst C. expansa will use laterally connected floodplains to move between river channels. We plan to track an additional 53 turtles for up to 5 years. This information will improve our understanding of turtle movement in response to flow and investigate if any water management strategies are required to support any clear movement patterns in these species.