Consequences of Dam Removal on Mussel Assemblages (Unionidae) in the Cuyahoga River

Abstract

The primary objective of a new survey of the Cuyahoga River was to assess species richness and population abundance of various mussel species in the family Unionidae throughout the Middle Cuyahoga River and upper parts of the Lower Cuyahoga River. Historically, few records existed for this river between Lake Rockwell and the Cuyahoga Valley National Park, a region in which four dams have been removed in the past 12 years. Timed visual surveys were conducted during low flow conditions and by using tactile techniques in deeper water. Throughout the survey, only 37 live animals were located across the 18 Middle Cuyahoga River sites inspected, which included only Lampsilis siliquoidea, Pyganodon grandis and the state-endangered Ligumia nasuta. No live mussels were found between the Gorge and the Cuyahoga Valley National Park. That 434 shells and valves were collected, and all but two were classified as long dead, attests that mussels had been more abundant, and that at least nine of the ten species known to be present above Lake Rockwell had lived in the Middle Cuyahoga River. Remote sensing data and aerial photographs were used to characterize change in opening up the river, but benefits to water quality and stream flow subsequent to dam removal must be tempered with the apparent loss of an assemblage of mussels better adapted to lentic conditions.