Predicting suitable habitat for surrogate species of critically imperiled freshwater mussels to aid in translocations

Freshwater mussels are among the most imperiled freshwater taxa, and translocation of these endangered species is one option for conservation. However, the long-term success of translocations is difficult to determine, in part because the amount of suitable habitat for a translocated species is often not known. Two federally endangered freshwater mussel species, the Northern Riffleshell Epioblasma rangiana (Lea, 1837) and the Clubshell Pleurobema clava (Lamarck, 1819), were recently translocated to the Middle Fork and Salt Fork of the Vermilion River in East Central Illinois, USA; however, the total amount of suitable habitat in both rivers remains unknown. To identify potential suitable habitat for these mussels in the Middle Fork and Salt Fork of the Vermilion River, we sampled 79 sites for surrogate mussel species of E. rangiana and P. clava along with their host fishes. We investigated habitat suitability by modeling presence/absence and abundance of surrogate mussel species to determine the landscape variables most strongly associated with surrogate mussel species presence/absence and abundance. We used these model results to create a habitat suitability index. We then validated our model predictions using timed searches in y 2 of our study. Our results indicate there may be more suitable habitat than previously believed throughout both rivers and that ample habitat is available to support large populations of mussels. Our approach also demonstrates how landscape variables can be used to successfully identify potential sites for future translocations.