Thesis (M.S.)--University of Wisconsin -- La Crosse, 2009. / Includes bibliographical references (leaves 44-46)

Yellow perch (Perca flavescens) exhibit an estrogen stimulated sexual sizedimorphism (SSD) wherein females grow faster and larger than males. In an effort togain better understanding of this phenomenon, several genes associated with sexualdevelopment, reproduction and growth were cloned, including prolactin (PRL),somatolactin (SL), insulin-like growth factor-I (IGF-Ib), the estrogen receptors (ER?? andER??a) and ovarian aromatase (CYP19A1). Real-time quantitative PCR (qPCR) assaysfor all the genes listed above, plus growth hormone (GH), were developed to measuremRNA levels in pituitary, liver and ovary.Adult fish were collected from Lake Erie in the spring (May) and autumn(October) over two years and tissue mRNA levels, body weight, age, gonadasomaticindex (GSI) and hepatasomatic index (HSI) were determined. Sex-specific differencesincluded females having higher body weights, HSI and liver ER?? mRNA levels thanmales and males having higher liver ER??a and liver CYP19A1 mRNA levels thanfemales. Season had a significant effect on growth factors (GH and IGF-Ib), with highermRNA levels in spring, which corresponded with higher liver CYP19A1 mRNA levels.Ovary CYP19A1 mRNA levels, which were higher in autumn, had a significant negativecorrelation with GH and IGF-Ib mRNA levels and liver ER??a mRNA levels had asignificant positive correlation with IGF-Ib mRNA levels.A brood of juvenile yellow perch was sampled through the first year ofdevelopment up to 421 days post-hatching (dph). There was a significant effect of dphon body weight, GH, PRL, SL, IGF-Ib, liver ER??, liver ER??a and ovary CYP19A1mRNA levels. Only liver ER??a mRNA had a significant effect of sex and exhibitedsignificant differences between males and females at 379 and 421 days post-hatching(dph). This work on yellow perch can provide predictive capabilities for estrogendependentphysiological processes in other species, especially teleosts, and can also makeyellow perch an exciting option for future ecotoxicogenomic studies.

This study evaluates the life history responses of yellow perch to mass removal and the potential for population recovery. We removed approximately 94% of a perch population from Nepawin Lake, a 35 hectare oligotrophic lake in Algonquin Provincial Park, Ontario, as part of a study designed to enhance the recruitment success of brook trout. Several response variables were examined both before and after mass removal: (1) condition, which includes growth, diet and overall condition responses, and (2) reproduction, which includes size at maturity and fecundity. We examine the question of whether compensatory life history responses in the yellow perch will overcome brook trout predation leading to a reestablishment of a high density perch population. Results showed that prior to the manipulation, perch exhibited a narrow size distribution, high dietary overlap, and low condition, typifying a stunted population. After mass removal, the perch population remained in a narrow size distribution, exhibited decreased growth rates for older age classes, showed increased mean condition and increased consumption of zooplankton in all size classes. Perch also exhibited increased size at maturity and decreased fecundity immediately following the mass removal. A time lag is expected before compensatory recruitment is possible in the population, but it is likely that the perch will recover from the mass removal because of strong age 0+ and 1+ cohorts. However, stunting and bottlenecking may still occur in the population. Continued monitoring and management is necessary to observe further changes to the perch population dynamics in Nepawin Lake.

Food habits for yellow perch Perca flavescens were compared using current and previous diet studies from southern Lake Michigan index sites. Yellow perch were not gape limited but size-selective in consumption of the newly established round goby Neogobius melanostomus. Ingested fish ranged from 7 to 47% of the yellow perch's total length and 2 to 53% of their gape. Currently, yellow perch diets are dominated in volume by fish/fish products (85%), which is double from previous studies. Utilization of zooplankton and insect prey items in the yellow perch diet has decreased to <1% by volume in 2002, contrasting with previous consumption of 4 to 20% and 5 to 17%, respectively, from previous studies during 1971-1993. Yellow perch are exhibiting opportunistic, generalist feeding strategy that incorporates both exotic and native prey items, allowing the population to use multiple prey items with the changing prey base in Lake Michigan. / Department of Biology

Thesis (Ph. D.)--University of Washington. / Bibliography: l. 138-143.

Thesis (Ph. D.)--Wildlife and Fisheries Sciences Dept., South Dakota State University, 2009. / Includes bibliographical references. Also available via the World Wide Web.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / eContent provider-neutral record in process. Description based on print version record. Bibliography: leaves 176-188.

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