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Document Type

Thesis - University Access Only

Award Date

2007

Degree Name

Master of Science (MS)

Department

Wildlife and Fisheries Science

First Advisor

David W. Willis

Keywords

bluegill, bluegill reproduction, biology, bluegill population, south dakota, impoundments

Abstract

The bluegill Lepomis macrochirus is an important prey species and important sport fish. Therefore, knowledge of reproduction and subsequent recruitment is essential for fishery biologists. Bluegill are typically considered multiple spawners. Protracted reproduction is likely a response to various environmental factors and may influence subsequent recruitment. However, little is known about bluegill spawning periodicity in eastern South Dakota impoundments. Thus, the objectives of this study were to 1) determine the best aging structure for eastern South Dakota bluegill populations, 2) relate bluegill recruitment patterns to abiotic (i.e., climatic) factors, and 3) assess the extent and duration of the bluegill spawning season in four eastern South Dakota impoundments. For the first objective, bluegills were collected from two small South Dakota impoundments. Little Moreau Lake is a 15-ha impoundment in Dewey County and Lake Louise is a 66-ha impoundment located in Hand County. All fish were collected during standard trap-net surveys conducted by the South Dakota Department of Game, Fish and Parks personnel. Scales provided age assignments similar to those from sagittal otoliths over the first 5 years of bluegill lifespan. However, scale ages were consistently underestimated for older bluegills in comparison with the otoliths (a validated aging structure). When accurate age-structure assessment or mortality rate determination is required, I recommend that South Dakota bluegill populations be aged with sagittal otoliths. The second objective of the study involved quantification of recruitment patterns and modeling of relations between climatic variables and year-class strength. Bluegills were collected from four impoundments during the summer of 2004 using trap nets. The residual method, based on otolith age structure, was used to index relative year-class strength of bluegill cohorts by population. Relations between year-class strength and climatic variables were assessed based on a priori models and Akaike’s information criterion analysis. Because year-class strength of many species in the northern Great Plains can be erratic due to abiotic factors, I hypothesized that weather patterns during critical times of the year may affect bluegill survival and thus subsequent recruitment. I found that bluegill recruitment patterns in these four impoundments functioned on an individualized scale. I then assessed the extent to which climatological patterns were related to bluegill recruitment. Akaike weights were comparable among all six a priori models that I developed. All single variables models (mean temperature, total precipitation, and cooling degree days) exhibited similar support and of the three single variable models, precipitation was the most supported. However, the bivariate plot between precipitation and recruitment exhibited a positive trend. Thus, if climatological factors influence bluegill recruitment patterns in South Dakota impoundments, the factors are likely complex and interrelated. For the final objective, larval bluegills were collected from four impoundments during the spawning seasons of 2005 and 2006 using a 0.75-m diameter ichthyoplankton net with a flow meter mounted in the mouth of the trawl to estimate larval density. Ages of larval fish were quantified using sagittal otoliths to determine hatch date. Peak larval bluegill abundances were highly variable among populations during both years. In 2005, peak larval abundances were unimodal and peaked in late June in all impoundments. However, in 2006 larval abundances had multiple modes in three out of the four impoundments. Based on otolith daily ring counts we estimated that bluegill populations had spawning durations as short as 38 d and as long as 77 d over the two years of my study. The differential timing of bluegill spawning in different years might have implications not only for bluegill recruitment but also for predators such largemouth bass Micropterus salmoides. The prolonged bluegill spawning season in 2006 may have provided an extended length range of prey for age-0 piscivores, thereby increasing their chances of overwinter survival.

Library of Congress Subject Headings

Bluegill -- South Dakota
Fish populations -- South Dakota

Description

Includes bibliographical references (page 46-52)

Format

application/pdf

Number of Pages

64

Publisher

South Dakota State University

Rights

Copyright © 2007 Kris R. Edwards

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