Fish assemblages in a network of ephemeral creeks in the regulated Edward/Kolety-Wakool River system in the southern Murray-Darling Basin were surveyed using conventional methods (backpack electrofishing and fyke nets) in conjunction with eDNA metabarcoding prior to, and after a major flood event. Prior to these surveys all fish monitoring and research had been focused on permanent river channels within this system.
Six creeks were sampled in August/September 2022 and again in May 2023 following widespread flooding during the spring and summer of 2022. Native fish declined sharply in both species richness and abundance during the post flood surveys resulting in the fish community being dominated by invasive species. This negative impact presents adaptive management challenges for environmental water managers in these systems.
Using eDNA metabarcoding as a complimentary survey method proved valuable in detecting large bodied native species that evaded detection using conventional physical methods and provides a promising approach for ecologists studying species that may be cryptic or occurring in low abundances.