Individual nesting male smallmouth bass (Micropterus dolomieui) in Lake Opeongo, Ontario, were followed for 11 years to determine the degree of nest-site fidelity from one year to the next. Only data from males nesting for the first and second time in consecutive years were included. The data indicate that 21.4% of all first-time nesting males returned to nest the following year. Nesting males rarely skipped a year after their 1st year of nesting. There was a strong tendency for males to return close (<20 m) to their previous year's nest site. Approximately 81 % renested within 200 m of their previous nest site, while the remainder nested between 200 and 1200 m from their previous nest site. This is the first report of nest-site fidelity for individual fish and is similar to published accounts of nest fidelity in birds.
This paper examines the concept and definition of fish stocks and the processes that influence discreteness of these stocks in light of the tactics necessary for the application of the concept in management. Two approaches to the definition of stocks are discussed. These differ in the extent to which management inputs other than biological ones are considered. We consider definition to be less important than the adoption and development of a stock concept to provide a genetic perspective for fisheries management. The two central levels of the stock concept — the subdivision of species into local populations and the adaptive nature of genetic differences between these populations — are discussed with respect to the interlinked set of ecological and genetic processes that result in subdivision and determine the discreteness of these stocks. Genetic discreteness usually implies some restriction of gene flow, and spatial and temporal mechanisms of isolation are discussed with examples from the STOCS symposium. The structure of subdivided populations is seen as the result of behavioral processes that are one component of a set of coadapted traits, which collectively constitute a life history strategy. The necessity for managers to develop a new integrated view of species, which incorporates both ecological and genetic arguments, is discussed.Key words: stock concept, life history, gene flow, ecological and genetic discreteness, local adaptation stock management
Evidence for species interactions in communities with Perca and Stizostedion is evaluated. Substantial evidence exists for the importance of predation by and on percids to community structure and function. Some evidence also clearly demonstrates that competition is an important interaction both within Perca populations and between Perca and other species. The necessity of using manipulative experiments to test for community level effects of competition and predation is emphasized. Such manipulative experiments, however, should be restricted in number and conducted with great care, because the community changes they induce are often irreversible and detrimental.Species interactions related to feeding have apparently resulted in the partitioning of habitat and food resources among fishes in percid communities. Partitioning of space is considered in terms of distribution of Perca and Stizostedion in respect to temperature in stratified and unstratified aquatic systems. In stratified lakes, percids are expected to be spatially segregated from fishes with other thermal requirements, such as the warmwater centrarchids and the cold-water salmonids. Seasons and depths of potentially intense interactions are diagrammed. In unstratified lakes, latitude and lake size set the stage for the thermal habitat that favors the physiology of percids in some systems. Resource partitioning, in respect to food size and time of day for foraging, is also diagrammed and appears to be important. It is argued that species interactions between other fishes and Perca and Stizostedion are greatly reduced by present patterns of resource utilization. Key words: competition, predation, resource partitioning, percid communities
This paper attempts to develop a biological basis for the management of stocks of lake trout (Salvelinus namaycush). Recent studies of the influence of genetic differences on the survival of planted stocks of trout and of the spatial distribution and movements of lake trout populations are reported. The genetic origin of planted lake trout influenced their survival in four Ontario lakes, whereas water hardness of the rearing hatchery had little effect. Survival also appeared to be influenced by the status of the native population but growth rates of native and introduced trout were similar. Age of first maturity appeared to differ between stocks in Lake Simcoe. Studies with both numbered and sonic tags in Lake Opeongo suggested that lake trout do not home to their natal shoal. Differences in total distances travelled were observed between sexes, but both males and females moved between shoals at spawning time. In Lake Simcoe, planted trout dispersed widely, colonizing spawning shoals up to 30 km from release sites, and no differences between stocks in time of spawning could be detected despite apparent differences in the home lakes. Temperature influenced spawning time and accounted for most of the timing variation between two allopatric lake trout stocks.Key words: lake trout, native, introduced, survival, growth rate, spawning distribution, movement, homing
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