Using sonar habitat mapping and GIS analyses to identify freshwater mussel habitat and estimate population size of a federally endangered freshwater mussel species, Amblema neislerii, in the Apalachicola River, FL

Abstract

Identification and quantification of freshwater mussel habitat in large turbid rivers is challenging. Sonar habitat mapping offers a low cost and time efficient means to identify and quantify benthic habitats over large spatial extents. I used sonar to classify freshwater mussel habitat across a 700 hectare reach of the Apalachicola River, FL, and used sonar imagery collected before and after a 10-year flood event to assess habitat stability. GIS-derived metrics and survey data were used to develop predictive models of presence/absence and abundance for the federally endangered freshwater mussel, Amblema neislerii. Strong associations were identified between habitats representing flow refugia, as well as deep water habitats. I validated predicted abundances with data from an independent, quantitative study. Suitable A. neislerii habitat as revealed by this approach was much larger than identified in previous studies, as was the resulting reach-wide population estimates of 7-8 million individuals.