Distribution of freshwater mussels (unionida: hyriidae) in coastal southeastern Australian rivers and impacts of landscape modification on conservation status

Abstract

This thesis clarified the geographic distributions of freshwater mussels in southeastern Australia, identified macroecological factors influencing distributions, and examined evidence for species declines. Fish-host preferences were determined for mussels, whose larvae are obligate parasites of fishes. IUCN Red List criteria was used to assess the conservation status of nine species. Museum records supplemented with survey data, revealed patchy distributions within and among river basins for some species. These spatial patterns could only be partially explained by habitat suitability modelling using bioclimatic, hydrologic and geomorphic variables. The northern range limits of Cucumerunio novaehollandiae and Hyridella spp. corresponded to a sharp transition in climate and an increase in hydrological variability. The distribution of Velesunio ambiguus matched the availability of lentic habitats in low-relief landscapes. Logistic regression modelling provided evidence of regional declines in freshwater mussel populations linked to human alteration of the landscape. An intensive survey of the Hunter River basin revealed a loss of species from reaches that have undergone catastrophic channel change. The host-parasite relationship for three hyriid species was not highly species specific, a feature that would facilitate mussel dispersal in disturbed landscapes. Glochidiosis was detected in 10 of 13 species of wild-caught fish and confirmed by artificial infections.