Degree Name

Master of Science (MS)

Semester of Degree Completion

Summer 2020

Thesis Director

Robert E, Colombo

Thesis Committee Member

Eden L. Effert-Fanta

Thesis Committee Member

Eric K. Bollinger

Abstract

The Blue Sucker, Cycleptus elongatus, occurs in large rivers primarily in the Mississippi River basin. Their imperiled status has called attention to the need for its management and protection. Estimating age is crucial for directing management, but past studies have varied in their choice of hard structure, resulting in uncertainty regarding the basic life history of this species. Because the Wabash River Blue Sucker population may be one of few surveyable populations with high abundance and successful reproduction, their demographics can provide a benchmark against which threatened populations can be compared. We harvested Blue Suckers (n = 168) from the lower Wabash River and compared age estimations from multiple hard structures. Otoliths yielded more precise and credible age estimates than other structures. Otoliths assigned ages up to 42 years. Annual mortality was 4.5%, and growth was modeled as TL = 680.29038 ∙ (1 - e( -0.15898 ∙ Age + 5.14037)), where TL = total length (mm) and Age = otolith age (years). Fecundity averaged 110,933 eggs/female. The population length-weight regression was Log10(WT) = 3.323 ∙ Log10(TL) - 5.9592 where WT = weight (g) and TL = total length (mm). Average relative weights followed a declining trend from 2008 to 2019, and this trend was mirrored in the declining average conditions of four other benthic invertivorous fishes in the Wabash River. We suggest that Blue Suckers can serve as bioindicators for the Wabash River ecosystem and their declining relative weights should be regarded as early symptoms of community level change.

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