Master's Theses

Department

Biology

Degree Name

Master of Science (MS)

Abstract

Most walleye Sander vitreus populations in Kansas are supplemented or sustained with stocking. In 2006, gamete collection for hatchery production was initiated at Cedar Bluff Reservoir because the walleye population has a high abundance of potential brood fish and has been sustained by natural reproduction since 2001. However, no quantitative index has been developed to assess walleye recruitment in this fishery. Accordingly, from July through November 2010, I evaluated catch-per-unit-effort (overnight sets) of age-0 walleye in 19 and 25-mm mesh gill nets biweekly and at random and standard sites. There was not a significant difference in catch-per-unit-effort between site types (t = -0.04, df = 142, P = 0.97) or mesh sizes (n = 144, U = 2,154, P = 0.07). Recruitment also can be evaluated with a one-time age structure sample. Therefore, the precision among age estimates was evaluated through taking a sample of 95 walleye: (1) by comparing age estimates between two readers, and (2) the consistency of estimates from one reader among hard structures, by evaluating age bias plots, age frequency tables, and coefficients of variation derived from scales, sagittal otoliths, and sectioned sagittal otoliths. Best fit regression slopes from age bias plots derived with otoliths and sectioned otoliths were not significantly different from a slope of one (t = 1.39, df = 2, P < 0.01; t = 0.44, df = 2, P < 0.01) suggesting strong agreement among estimates. However, the best fit regression slope derived by using scales was significantly different from one (t = -3.42, df = 2, P < 0.01), suggesting scales did not provide adequate precision for additional recruitment analyses. Age structure data were utilized, ages estimated from 210 fish (5 to 6 individuals in each 10 mm length group) and then extrapolated to a sample of un-aged fish (n = 928) based on size classes, to evaluate recruitment variability with the Recruitment Variability Index. The Recruitment Variability Index estimate was 0.69 and similar to estimates from over a decade earlier suggesting consistent recruitment in this population. An age structure was also used and historical catch-per-unit-effort of age-0 walleye to evaluate their utility in predicting year-class strength. Historical catch-per-unit-effort of age-0 walleye explained 72% (adjusted r2 value) of the variation in the current estimated size of the corresponding year-classes (F = 29.29, df = 11, P < 0.01). Natural reproduction appears to be sustaining both walleye population and gamete harvest at Cedar Bluff Reservoir.

Keywords

walleye, recruitment, otolith, recruitment variation index, cedar bluff reservoir

Advisor

Dr. Robert Channell

Date of Award

Spring 2012

Document Type

Thesis

Rights

© The Author(s)

Comments

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