Background/Aims
Climate change is increasing aridity and altering the hydrological regimes of rivers in mediterranean climate regions globally. In southwestern Australia this is highly pronounced, resulting in prolonged seasonal drying and reduced surface flows, threatening the persistence of perennial refuges in rivers which are crucial to the resilience and recovery of fish metacommunities. Artificial perennial waterbodies have potential to offset the loss of natural refuges under increasingly frequent and severe drought events.
Methods
To evaluate their potential, native fish assemblages in a high conservation value intermittent tributary of the Denmark River, Western Australia, were repeatedly sampled in two consecutive baseflow seasons when fish populations were confined to four isolated refuges (one natural and three artificial) between April 2024 and March 2025. The 2024 baseflow sampling event coincided with a prolonged seasonal drought, representative of the future climate conditions predicted for this region.
Results
Substantial declines in the abundance of most fishes and the structure of the fish metacommunity were observed between the two baseflow seasons, primarily driven by a 70% reduction in N. pygmaea and a 30% increase in N.balstoni. The natural site suffered the greatest losses in abundance and diversity. Environmental filtering during pool isolation associated with drought substantially impaired the ability of most native fish species to recover to pre-drought levels before the 2025 baseflow season. Importantly, artificial refuges appear to better protect fish from drought-mediated environmental filtering than the natural pool.
Conclusion
Our results suggest that artificial refuges play an important role in maintaining gamma diversity in intermittent river networks by replacing lost natural refuges, or by increasing the number of refuges within catchments. Real benefits could be obtained by strategically increasing the number of artificial refuges in southwestern Australian as a key conservation strategy to support the southwest’s highly imperilled endemic freshwater fishes.