Abundance and nutritional status of freshwater turtles to guide delivery of environmental flows in the Murray-Darling Basin, south-eastern Australia

Almost half of Australian freshwater turtle species are formally listed as threatened, but little is known about the effects of water management and other factors on the abundance and health of freshwater turtles in arid and semi-arid regions. This study investigated how river flows (including the controlled release of water from an upstream storage facility, or 'environmental flow') and water quality might affect the abundance and nutritional status of three freshwater turtle species in three dryland rivers of the Murray-Darling basin in south-eastern Australia. No response in abundance or nutritional status of the broad-shelled turtle, Chelodina expansa, the eastern long-necked turtle, Chelodina longicollis, and the Macquarie turtle, Emydura macquarii, was detected in relation to river flows, possibly because of the small magnitude of the environmental flow. However, for C. expansa, the catch per unit effort (CPUE) was negatively related to increasing macrophyte cover, electrical conductivity (EC, an indicator of salinity), and turbidity. CPUE for C. longicollis was positively related to macrophyte cover and EC, and for E. macquarii it was positively related to macrophyte cover. Haematological measurements suggested that the turtles had healthy nutritional status. Body condition and blood glucose and protein were related significantly to EC, whereas haematological measurements varied significantly among species and between spring and summer. The main conclusion is that water management measures to help the conservation of these turtles should include sufficient environmental flow to produce overbank flooding, thereby creating and maintaining a wide range of habitat suitable for the differing needs of the individual species.

Automated summary

This study investigated the effects of river flows and water quality on the abundance and nutritional status of three freshwater turtle species in dryland rivers in Australia. The results showed that the abundance and nutritional status of the turtles were not significantly influenced by river flows, but were related to factors such as macrophyte cover and electrical conductivity. Hematological measurements suggested that the turtles had healthy nutritional status.