Graduate Program

Biological Sciences

Degree Name

Master of Science (MS)

Semester of Degree Completion

Spring 2021

Thesis Director

Robert E. Colombo

Thesis Committee Member

Anabela Maia

Thesis Committee Member

Thomas Canam

Abstract

The Sangamon River flows across central Illinois and is mostly free flowing except in the city of Decatur where it is impounded to form Lake Decatur. The Sanitary District of Decatur (SDD) is located approximately three miles downstream of the Lake Decatur dam. For a significant portion of the year, the stretch of the Sangamon River downstream of SDD is dominated by effluent due to limited discharge from the Lake Decatur dam. This has resulted in heavy nutrient loading, most notably phosphorus, and elevated levels of nickel and other compounds in the downstream section of the river. Smallmouth buffalo (Ictiobus bubalus) exhibiting elongated fins have been observed in this section of the river. To test for causality between fin elongation of fish in the Sangamon River and SDD effluent, a microcosm experiment was designed to raise Fathead minnows (Pimephales promelas) in wastewater effluent at SDD as well as the City of Charleston, Illinois Wastewater Treatment Plant (CWTP). Additionally, a control group of Fathead minnows were reared in dechlorinated tap water. Results from the experiment indicated that fish raised in SDD effluent had significantly longer fins at a given body length than fish from all other treatments. Furthermore, fish in the control treatment experienced faster growth than all other treatments; however, according to Le Cren’s relative condition factor, Decatur treatment fish were in the best condition. To assess the effect of fin elongation on active metabolic rate (AMR) and critical swimming speed (Ucrit), Smallmouth buffalo (n = 9) participated in swimming trials in a 185 L Loligo Systems flow chamber. Results indicate that there was a significant negative linear relationship between caudal fin size and AMR, indicating that fish with elongated fins are more efficient swimmers. The relationship between caudal fin size and Ucritvalues was not significant, indicating that caudal fin size is not a predictor of critical swimming speed.

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