Graduate Program

Biological Sciences

Degree Name

Master of Science (MS)

Semester of Degree Completion

Spring 2021

Thesis Director

Robert E. Colombo

Thesis Committee Member

Scott J. Meiners

Thesis Committee Member

Eden L. Effert-Fanta

Abstract

Dams affect the abundance of fish species in lotic systems by altering flow regime and available physical habitat. Removal of dams may mitigate these effects and generate a change in species abundance and fish community structure. Understanding the effects of dam removal on gamefish species is essential in making management decisions. I investigated how populations of Smallmouth Bass (Micropterus dolomieu), Spotted Bass (M. punctulatus), and Largemouth Bass (M. salmoides) were affected by the presence and removal of two low-head dams in a Midwestern river system. I used data collected during fall and spring from 2012-2015 (pre-removal) and 2018-2019 (post-removal) using multiple gear types at six study sites on each river; two within the run-of-river reach, two within the impounded reach, and two within the downstream reach. I analyzed species abundances using a nested ANOVA with fixed factors of season, reach, and dam removal, within the random factor of river. The interaction of season and treatment factors, along with all other individual factors, significantly affected Smallmouth Bass abundance. Only the interaction of season and treatment factors affected Largemouth Bass abundance, and only the factor of season affected Spotted Bass abundance. Impounded reaches had lower Smallmouth Bass abundance pre-removal. Overall Smallmouth Bass abundance increased post-removal, while Largemouth Bass and Spotted Bass abundance decreased. These results demonstrate an immediate response in a sport fishery to dam removal and suggest that Smallmouth Bass may benefit from dam removal as a form of habitat restoration and gamefish management.

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