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.

Nodularin (NODLN) is a pentapeptide produced by the filamentous cyanobacterium Nodularia spumigena that is a bloom-forming species in the Baltic Sea. NODLN is an intracellular hepatotoxin, which can have a negative effect on aquatic life including fish. Toxins are released into the water when cells are lysing, e.g. during a decaying bloom. N. spumigena filaments have previously been shown to have a negative effect on perch egg development and perch larval survival. Coastal fish such as perch (Perca fluviatilis) have suffered from recruitment problems in the Baltic Sea the last decades. However, little is known about the impact of toxic cyanobacteria on juvenile perch. In the autumn of 2007, 1+ perch were exposed, during 29 days to either whole live cells (WC) or a crude extract (CE) of broken N. spumigena cells. Chlorophyll a concentrations in the aquaria were 50 µg L -1. Perch were fed chironomidae larvae twice a day. Unexposed perch either fed (CoF) or without food (Co) served as controls. Length and weight of perch were measured at onset and termination of experiment. NODLN content was measured in N. spumigena filaments, crude extract and perch liver samples using liquid chromatography-mass spectrometry (LC-MS). Total lipids (TL) were extracted and quantified from whole-body lyophilised perch excluding livers. No significant differences for length and weight of perch were found between treatments and fed control. NODLN was detected in the crude extract samples, while no NODLN was detected in the perch livers. Moreover TL determination revealed no significant differences between treatments and fed control. Nodularia spumigena did not affect perch in this experiment, probably due to that the critical period of the first year for the perch was exceeded. Therefore, 1+ perch was not as susceptible to the cyanobacterium as eggs, larvae and younger juveniles of fish found in the literature. Perch liver did not contain NODLN, thus either the toxin was detoxicated with no recorded energetic cost or it was not ingested. The variables studied here did not show any effects of NODLN. However, other chemical methods such as enzymatic activity may disclose effects of NODLN.

<p>Nodularin (NODLN) is a pentapeptide produced by the filamentous cyanobacterium <em>Nodularia spumigena</em> that is a bloom-forming species in the Baltic Sea. NODLN is an intracellular hepatotoxin, which can have a negative effect on aquatic life including fish. Toxins are released into the water when cells are lysing, e.g. during a decaying bloom. <em>N. spumigena </em>filaments have previously been shown to have a negative effect on perch egg development and perch larval survival. Coastal fish such as perch (<em>Perca fluviatilis</em>) have suffered from recruitment problems in the Baltic Sea the last decades. However, little is known about the impact of toxic cyanobacteria on juvenile perch. In the autumn of 2007, 1+ perch were exposed, during 29 days to either whole live cells (WC) or a crude extract (CE) of broken <em>N. spumigena</em> cells. Chlorophyll <em>a </em>concentrations in the aquaria were 50 µg L ^-1. Perch were fed chironomidae larvae twice a day. Unexposed perch either fed (CoF) or without food (Co) served as controls. Length and weight of perch were measured at onset and termination of experiment. NODLN content was measured in <em>N. spumigena </em>filaments,<em> </em>crude extract and perch liver samples using liquid chromatography-mass spectrometry (LC-MS). Total lipids (TL) were extracted and quantified from whole-body lyophilised perch excluding livers. No significant differences for length and weight of perch were found between treatments and fed control. NODLN was detected in the crude extract samples, while no NODLN was detected in the perch livers. Moreover TL determination revealed no significant differences between treatments and fed control. <em>Nodularia spumigena</em> did not affect perch in this experiment, probably due to that the critical period of the first year for the perch was exceeded. Therefore, 1+ perch was not as susceptible to the cyanobacterium as eggs, larvae and younger juveniles of fish found in the literature. Perch liver did not contain NODLN, thus either the toxin was detoxicated with no recorded energetic cost or it was not ingested. The variables studied here did not show any effects of NODLN. However, other chemical methods such as enzymatic activity may disclose effects of NODLN.</p><p> </p>

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.

Yellow perch, Perca flavescens (Mitchill), were collected for food habit determination from a transect in Indiana waters of Lake Michigan near Michigan City, Indiana between June and October in 1971 and June and September in 1972.The most important food items utilized on a mean annual basis were: unidentifiable organic material (UOM), alewife eggs, Pontoporeia affinis, fish (primarily alewife), insects (primarily chironomid larvae and pupae), and Eurycercus lamellatus. E. lamellatus, alewife eggs and UOM dominated 1971 stomach contents with P. affinis more important than E. lamellatus in 1972.Monthly stomach contents revealed heavy consumption of alewife eggs when available during the alewife spawning period, but these were replaced by P. affinis and fish (alewife) especially after July in both years.Differences between sexes of yellow perch captured by day and by night were minor and inconsistent.Differences between selected size groups (100-175, 176-225, 226-275 mm) manifested themselves in greater use of larger food items such as P. affinis and fish with larger length groups and as the summer progressed. The mean volumes of alewife eggs consumed, the most important food of yellow perch in this study, decreased significantly within each month both years as length of the yellow perch increased. In the large length groups, greater use of larger food items was made, but only fishes as a food item showed a signigicant difference between the two larger length groups.

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

Yellow perch, Perca flavescens, were collected by night trawling and gill netting at 5 m in a study area near Kintzele Ditch in Indiana waters of Lake Michigan during the months of June through September, 1975. Additional collections made by the Indiana Department of Natural Resources and the U.S. Fish and Wildlife Service using gill nets were included in some aspects of the study.Population characteristics were analyzed and compared to other studies. The rate of growth was significantly greater than in past Great Lakes' populations. The calculated length-weight relationships and growth rates were comparable to those reported by recent studies for southern Lake Michigan. Growth differed between males and females of the same age, and different ages were often represented in the same length interval. Nearly all male yellow perch were mature by age I and 130 mm. About half of the age II females and most at the 200 mm length interval were mature. Sex ratios were variable.Higher catch-per-unit-effort (cpe) was related to warmer water temperatures to the thermocline level. When water temperatures were mixed resulting in low inshore temperatures, cpe values were lower.There existed a great deal of sample variability within and between gear types as a result of seasonal population availability, gear characteristics, and non-random distribution of the population.Trawling, although more efficient than gill netting at sampling total numbers and widest range of lengths, was selective for smaller fish, and gill netting was selective for larger fish. Depth (from 5 m to 18.3 m) and particular gill net methods employed had little effect upon the sizes and length-percent frequency distribution sampled.Great differences between percentage age compositions compiled from trawl and gill net catches reflected the size selectivity of the gears. These results raised questions concerning the validity of management techniques involving percentage age composition and cpe index values to determine relative year class strength.The age groups I and II were represented by the proportion 8:2 (1:11) in the trawl catch which adequately sampled the sizes including the age I and II fish. Further study would be needed to determine the validity and usefulness to management considerations of this method of relative year class strength determinations. Recommendations for additional study were made.

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

Thesis (Ph. D.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains iii, 33 p. : ill. Includes abstract. Includes bibliographical references (p. 17-21).

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