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Offspring size determines offspring survival rates; thus, understanding factors influencing offspring size variability could elucidate variation in population dynamics. Offspring size variation is influenced through multigenerational adaptation to local environments and within-lifetime plastic responses to environmental variability and maternal effects among individuals. Moreover, offspring size variation may represent trade-offs in energy allocation within individuals that influence lifetime reproductive success. However, the mechanisms whereby environmental conditions influence offspring size, e.g., via inducing adaptive and plastic variation in population-scale maternal effects, remain poorly understood. We evaluated intra-specific variation in maternal effects, egg size, and intra-individual egg size variation in six populations of walleye ( Sander vitreus) and related among- and within-population patterns to thermal conditions. Egg size was conserved within populations and negatively related to long-term thermal conditions among populations, while maternal effect strengths were positively related to thermal conditions, suggesting that populations inhabiting warmer environments adapted to produce smaller eggs but stronger maternal effects. Within a population, egg size was positively related to colder winters, suggesting cold winters may alter egg size through effects on maternal condition or as an adaptive maternal effect to improve offspring survival. Intra-individual egg size variation varied little among populations or with female size, but declined with increasing summer and decreasing winter temperatures. Our result suggests that environmental conditions could impact not only short-term offspring production but also spur adaptive changes in offspring phenotypes. Thus, it is necessary to account for adaptive responses to predict population dynamics under environmental changes. [ABSTRACT FROM AUTHOR]

Assessment of predator-prey dynamics is a central feature of community-based fisheries management, and a variety of fish condition indices have been developed from length-weight data to make inferences about feeding conditions. Relative weight (Wr) is useful for measuring fish condition, is easily calculated, and has simple data requirements; however, few studies have empirically validated Wr indices. We compared the Wr of walleyes Sander vitreus in Oneida Lake, New York, with prey fish availability and walleye growth observed over 23 years (1961-1983). For each year, we calculated the Wr for three length-classes (350, 400, and 450 mm total length) of walleyes caught in October. Prey fish availability was calculated from annual estimates of (1) prey biomass in bottom trawl catch and (2) biomass of age-3 and older walleyes estimated from mark-recapture studies. Growth of walleyes (ages 4-6) was determined using lengths at age that were back-calculated from scale annuli. The Wr declined as walleye length-class increased, and W,. was positively related to both prey fish availability and walleye growth. Our study suggests that Wr can be a useful tool for describing feeding conditions and assessing predator-prey relations. [ABSTRACT FROM AUTHOR]

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Absolute estimates of stocked fish contributions to fisheries are important in determining the utility of stocking programs. Accounts of stocked fish contribution to fisheries are rare; such studies require (1) stocked fish to be uniquely marked so that they are identifiable when the cohort recruits to the fishery and (2) absolute abundance estimates to be available both from stocked fish and fish produced from other sources. Our objective was to assess the absolute contribution of walleyes Sander vitreus stocked as yearlings to the age-4 population in Oneida Lake, New York. Stocked yearlings contributed 1,778 fish to the age-4 population, which was estimated at 127,000. Estimated survival from stocking (age 1) to age 4 was 1.7% (range = 0.2-3.2%) and was similar to reports of the absolute contribution of fingerling stocking programs. Our results support findings from other studies indicating that attempts to strengthen walleye year-classes by stocking have had limited success; however, our data are based on only one year-class. Documented variability in stocking success on other systems warrants further investigation. [ABSTRACT FROM AUTHOR]

Angler catch rates have been used to compare angler success in sport fisheries among years or systems, to assess relative fish abundance, and to evaluate management efforts. Understanding the factors that influence angler catch rates is critical for the proper interpretation and application of these data. Information for 10,998 angler trips was collected through an angler diary program conducted during 1994-1998 and direct-contact roving creel surveys conducted during 1997 and 2002-2004 to examine the influences of angler party size and trip length on the catch rates for walleye Sander vitreus, smallmouth bass Micropterus dolomieu, and yellow perch Perca flavescens at Oneida Lake, New York. Party size and trip length were correlated; therefore, we constructed separate models combining data for year, party size, and trip length to examine the relationship between these factors and the angler catch rate. In both the diary program and the creel survey, the angler catch rates for all species decreased significantly as the party size increased. For diary program data only, trip length also was negatively related to the angler catch rate, but party size typically accounted for more of the variation in angler catch rates than did trip length. Our results indicate that when party size or trip length varies among systems or years, failure to account for these factors may hinder the ability to accurately measure and compare angler catch rates. In addition, angler catch rates calculated with data from roving interviews (incomplete trips) may be biased because of party size. Catch data should be collected from each angler individually for parties consisting of more than one angler. [ABSTRACT FROM AUTHOR]

Understanding the relationship between anglers and fish is important to the management of angling fisheries. We compared angler catch rates estimated from creel surveys with (1) population density estimates of age-3 and older walleyes Sander vitreus based on mark-recapture and (2) mean growth of walleyes aged 4-6 in Oneida Lake during 1957-1959, 1997, and 2002-2003. We also compared walleye catchability to walleye population density. Angler catch rates were not related to walleye population density; however, by combining population density and walleye growth, we were able to explain 97% of the variability in angler catch rates, perhaps because growth rates were related to prey abundance. Catchability of walleyes decreased as population density increased. Consideration of these effects should improve out understanding of angler-fish dynamics and allow fishery managers to better predict the effects of management actions. [ABSTRACT FROM AUTHOR]