1. Freshwater mussels are one of the most imperilled animal groups in the world. Their effective conservation and restoration require a better understanding of their spatial distributions at a relevant scale and of their relationships with natural environmental factors and human disturbances. 2. In this study, we sampled over 900 sites on wadeable streams throughout Illinois, U.S.A., and compiled environmental data for a wide range of natural and anthropogenic factors related to climate, geology, land use, and connections to large rivers, dams and ponds. 3. Using random forest classification and regression, we modelled the presence-absence of mussels as a group (87% accuracy), the abundances of 29 individual mussel species (R 2 = 0.2-0.51), species richness (R 2 = 0.52) and total mussel abundance in a standard sample (R 2 = 0.41). 4. The abundances of most species increased with stream size, the proportion of agricultural land in the catchment and the distance to the nearest dam or pond, but decreased with increasing catchment or channel slope and the proportion of forest in the catchment. Species varied in their relationships with climate variables, suggesting that they respond differently to climate change. Geology, particularly bedrock depth, was important for many species. Species richness and total mussel abundance responded positively to stream size and negatively to the slope of streams or catchments. 5. The models were applied to unsampled wadeable stream reaches to generate mussel distribution maps at the reach scale, useful tools for resource managers to effectively protect and restore mussel biodiversity. The models also improve our understanding of how mussel populations and assemblages are structured by natural factors and human disturbances at a broad scale.

Translocation of freshwater mussels is a conservation tool used to reintroduce extirpated populations or augment small populations. Few studies have evaluated the effectiveness of translocations, mainly because estimating survival is challenging and time-consuming. We used a mark-recapture approach to estimate survival of nearly 4,000 individually marked Clubshell (Pleurobema clava) and Northern Riffleshell (Epioblasma rangiana) translocated to eight sites over a five-year period into the Salt Fork and Middle Fork Vermilion rivers in central Illinois. Survival differed among sites and between species; Clubshell were approximately five times more likely to survive than Northern Riffleshell. Survival also increased in the fourth year following a release and decreased following high-flow events. Translocating numerous individuals into multiple sites over a period of years could spread the risk of catastrophic high-flow events and maximize the likelihood for establishing self-sustaining populations.

No abstract

No abstract