The Barwon-Darling River has a highly variable flow regime, fluctuating between highly productive ‘boom’ periods and ‘bust’ periods of lower productivity. During these ‘bust’ periods when flow is low, biota rely on remaining waterholes as refugia until the next ‘boom’ period when hydrologic connectivity allows for movement between waterholes. In these types of highly variable systems, there is evidence that some species exist in a metapopulation. Periods of connectivity are important events for maintaining local populations and re-populating areas where local extinctions may have occurred. In addition to the naturally high flow variability of the Barwon-Darling River, it also experiences multiple stressors including increased periods of low or no flow and competing ecological, economic, and social demands for a limited water resource.
Bony Herring (Nematalosa erebi) is a native Australian freshwater fish species that is abundant and widely distributed within the Barwon-Darling River. Given the highly variable nature of the river system, it is predicted that this species relies on periodic connection events to maintain individual populations and will exhibit weak genetic structure. Fin clips were collected along the main channel of the Barwon-Darling River from Mungindi to north of Menindee in 2018 and 2019. Single nucleotide polymorphism (SNP) markers were used to identify if there is genetic structuring of N. erebi within the Barwon-Darling River. A greater understanding of the population genetics of N. erebi is necessary to predict the capacity of this species to persist in the face of increasing environmental pressures.