Document Type

Dissertation - Open Access

Award Date

2006

Degree Name

Doctor of Philosophy (PhD)

Department / School

Wildlife and Fisheries Science

First Advisor

Michael L. Brown

Abstract

Walleye Sander vitreus is an important ecological component of glacial lake aquatic communities in eastern South Dakota, and the most popular sport fish in the region. Walleye populations in this region exhibit consistently poor or annually-variable reproductive success and are regularly stocked in an effort to maintain consistent recreational fisheries. However, current stocking programs are based on reproductive success from previous years rather than on expected reproductive success in the year which stocking occurs. Determination of walleye cohort strength at the larval life stage would provide a stocking prioritization system that would utilize the natural reproduction of in situ walleye populations, and maximize the potential benefits of stocked walleye by supplementing weak or failed cohorts. In consideration of these management issues, the objectives of this study were to: 1) evaluate the utility of three ichthyoplankton gears for estimating the strength of walleye cohorts at the larval life stage; 2) assess the interaction between yellow perch and walleye during their first year and 3) determine the factors influencing the reproductive success of South Dakota glacial lakes walleye populations. Three cohorts of walleye were sampled from spring to fall in each of three years (2001 to 2003). Sampling was conducted in Clear (Marshall County), Madison (Lake County), Parks (Day County), Sinai (Brookings County), and Thompson (Kingsbury County) lakes in the glacial lakes region of eastern South Dakota. Concurrent larval walleye and yellow perch samples were collected weekly from 1 May through 15 June using a 0.5-m conical plankton net, a Miller high-speed fry sampler, and quatrefoil light traps. Juvenile walleye and yellow perch were collected bi-weekly from 1 July through 20 August with night-time seining; fall walleye collections consisted of a single night-time electrofishing trip during mid-September. Light traps captured substantially more larval walleye than either of the other two active ichthyoplankton (IP) gears. In general, light traps captured walleye yolk-sac larvae shortly after hatching (third week in May) and the conical net and Miller sampler captured walleye two weeks later. Precision of larval walleye abundance estimates was poor for all three IP gears. However, significant positive correlations were found between peak larval walleye abundance estimates from all three IP gears, suggesting that catch rates from all three gears varied in accordance with larval walleye abundance. Mean lengths of walleye larvae captured by each of the three IP gears reflected the differences in catch timing. Walleye captured with light traps were less than 11 mm and were generally larger than 13 mm in the two active IP gears. Peak larval walleye catch rates from all three IP gears showed highly significant (P<0.001) positive linear correlations to estimates of relative abundance of juveniles from both summer seining and fall electrofishing. Although, prediction of walleye cohort strength from larval sampling is plausible using any of the three IP gears, light traps show the most promise as a predictive tool. Light traps captured walleye larvae from weak to very strong cohorts, while the active gears only captured walleye larvae from strong to very strong cohorts. In addition, light traps capture newly-hatched yolk sac larvae during the same time of the year that state hatcheries are producing walleye fry for stocking. Predictions of cohort strength generated at this time could direct hatchery products to waters with weak or failed cohorts. That walleye cohort strength was correlated with larval abundance suggests that cohort strength was set before larval sampling occurred. Mortality of larvae to fall was likely high but occurred in a predictable manner. The absence of walleye larvae in IP samples from waters with failed cohorts suggests that cohort strength was determined by the number of walleye that hatch rather than catastrophic or episodic mortality occurring at the larval or juvenile life stages.

Library of Congress Subject Headings

Walleye (Fish) -- South Dakota

Description

Includes bibliographical references (page 99-111)

Format

application/pdf

Number of Pages

127

Publisher

South Dakota State University

Rights

Copyright © 2006 Richard D. Zweifel. All rights reserved.

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