Abstract
<title>Abstract</title> <p>Acid wetlands in coastal wallum country along the central-eastern coast of Australia are critical habitat for multiple threatened fish and frog species but are being increasingly exposed to severe drought and wildfire. Vast amounts of wallum habitat were affected by the 2019–2020 Black Summer bushfires, but the full impact of the fires on the aquatic fauna was uncertain. We surveyed 216 wallum wetland sites between 2020 and 2022 to assess patterns of occurrence and abundance in freshwater fish and amphibians in relation to fire severity, hydrologic persistence, invasive species, and other environmental factors. Using multivariate mixed modelling approaches, we evaluated species-specific responses to environmental variations and residual species covariation. Overall, most wallum fish and frog species did not exhibit strong negative responses to fire severity. For fish, responses to fire were geographically variable, with the direction and magnitude of impact changing along a latitudinal gradient, and species occupancy highly idiosyncratic among wetlands. In contrast, amphibian species covaried n in their distribution, and invasive cane toad abundance was a key factor affecting native amphibian abundance, particularly for wallum specialist species. Hydrologic variability and surface water persistence were more consistent drivers of amphibian abundance than fire alone, while pre-fire drying likely compounded impacts. Together, these findings indicate that wallum fish and frogs are broadly resilient to severe fire disturbance, reflecting long-term adaptation to a dynamic, disturbance-prone environment. The interaction of fire, hydrologic isolation and invasive species represents an ongoing risk to population persistence of native aquatic fauna in wallum wetlands.</p>