Development of a Multimetric Index for Fish Assemblages in a Cold Tailwater in Tennessee

Abstract

Tailwaters downstream of hypolimnetic-release hydropeaking dams exhibit a unique combination of stressors that affects the structure and function of resident fish assemblages. We developed a statistically and biologically defensible multimetric index of fish assemblages for the Caney Fork River below Center Hill Dam, Tennessee. Fish assemblages were sampled at five sites using boat-mounted and backpack electrofishing gear from fall 2009 through summer 2011. A multivariate statistical approach was used to select metrics that best reflected the downstream gradients in abiotic variables. Five metrics derived from boat electrofishing samples and four metrics derived from backpack electrofishing samples were selected for incorporation into the index based on their high correlation with environmental data. The nine metrics demonstrated predictable patterns of increase or decrease with increasing distance downstream of the dam. The multimetric index generally exhibited a pattern of increasing scores with increasing distance from the dam, indicating a downstream recovery gradient in fish assemblage composition. The index can be used to monitor anticipated changes in the fish communities of the Caney Fork River when repairs to Center Hill Dam are completed later this decade, resulting in altered dam operations.

Received July 25, 2013; accepted November 12, 2013

ACKNOWLEDGMENTS

Primary funding for this research was provided by the USACE. Additional funding and support were provided by the Center for the Management, Utilization, and Protection of Water Resources at Tennessee Technological University and by the Tennessee Cooperative Fishery Research Unit. The Tennessee Cooperative Fishery Research Unit is jointly sponsored by the U.S. Geological Survey, the U.S. Fish and Wildlife Service, the Tennessee Wildlife Resources Agency, and Tennessee Technological University. This manuscript benefited from the constructive comments offered by S. Miranda and three anonymous reviewers. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.