Experimental Habitat Enhancement and Monitoring for the Endangered Mary River Cod <scp> <i>Maccullochella mariensis</i> </scp>

ABSTRACT Artificial nesting structures were trialled to enhance reproductive habitat for endangered Mary River cod ( Maccullochella mariensis ) in Queensland, Australia. Twenty‐four hollow log structures of two designs were installed across six river sites and monitored alongside natural structures during the 2024 breeding season. Mary River cod used both designs, with one confirmed spawning event in an artificial log. While cod spawning was more frequent in natural structures, the artificial habitats supported multiple fish, reptile and frog species, potentially serving as cost‐effective, multifunctional refuges. Artificial structures can supplement lost or degraded habitat, offering a promising tool for the conservation of large threatened freshwater fauna.