Author Institution: Biology Department, Hiram CollegeA survey of union ids in Pymatuning Creek in Ashtabula County, OH, was conducted to assess the species present and their relative abundances, with particular attention to the federally endangered Clubshell (Pleurobema clava). Sampling the stream bed by hand at 18 locations produced 3,464 living and 501 dead unionids comprising 11 different species. At each site, data were collected for substrata types, and water depth, speed, temperature, pH, and oxygen concentration were measured. The mussel fauna consisted of two dominant species (JElliptio dilatata and Amblema plicata), three subdominants (Lasmigona complanata, Anodonta grandis grandis, and Ixi tufts His radiata luteola), and six uncommon species (Pleurobema clava, Lasmigona costata, Lasmigona compressa, Anodontoides ferussacianus, Anodonta imbecillis, and Villosa iris iris), listed in order of abundance. Living specimens of P. clava were found in habitats that were characterized by shallow water, good oxygenation, little organic debris, moderate current, and substrata consisting mostly of sand with fine pebbles. The relative abundance of mussels averaged 1.783 mussels found per minute of search time and ranged from 0.225 to 4.390, while previous studies of the Cuyahoga River yielded an average relative abundance of 0.469 mussels per minute of searching. The present survey indicates that Pymatuning Creek supports a large and vigorous population of unionids, and that P. clava comprises a small but healthy element of that fauna and may constitute Ohio's largest population of this endangered species
