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Ecology of the yellowstone cutthroat trout (Salmo clarkii lewisi Girard) in Kiakho Lake, British Columbia Stenton, Charles Ernest

Abstract

A knowledge of the basic biology of any fish is a primary requirement for the practical management of that stock of fish. This investigation was directed at a pure culture population of Yellowstone cutthroat trout, to describe the basic biology and provide a basis for management and further research. Kiakho Lake has a surface area of 67.42 acres, a maximum depth of 32 feet and a mean depth of 16.5 feet. Due to the rocky substrate, lack of littoral development and low total dissolved solids, the production of plankton and bottom fauna was small and characteristic of oligotrophic conditions. The food of cutthroat trout in Kiakho Lake in May was comprised of 83.9 percent by volume and 81.3 percent by occurrence of chironomid pupae. In June the food was 46.7 percent by volume and 45.8 and 35.5 percent by occurrence of chironomid larvae and Gammarus respectively. In July the Gammarus were 57.8 percent by volume and 60.3 percent by occurrence. In Lumberton Reservoir and Monroe Lake the Gammarus comprised 51.0 and 55.6 percent by volume and 34.4 and 78.2 percent by occurrence respectively of the food. In Garcia Lake, Chaoborus was 32.9 percent by volume and 36.0 percent by occurrence and the redside shiner, Richardsonius balteatus, was 27.8 percent by volume and 31.8 percent by occurrence. The fish appeared to be second in preference to Chaoborus. The body-scale relationship is described by a straight line having a slope of 1. A graph of instantaneous growth rate plotted against length, revealed that faster growing fish have a faster decrease in growth rate. Due to the absence of certain characteristics e.g. a concavity in the upper limit of the graph, the growth of Kiakho Lake cutthroat appeared to support the view that faster growing fish are selected by the fishery, and that it can be demonstrated in this type of graph. The data, fitted to a Parker and Larkin (1959) growth equation gave a z value of 0.71. The absence of "Lee's Phenomenon" gave support to the premise that the phenomenon can result from selection by a fishery, and invalidated the other ideas concerning the causes as far as this population was concerned. The spawning run in Kiakho Lake was estimated at 3,000 fish. A tagging program revealed that the fish spent on the average of 13 days to spawn, and that there was approximately a 54 percent mortality. The male fish appeared on the spawning grounds first. The female fish showed a decrease in size, later in the run, which was not shown by the males. The eggs hatched sometime in mid June and the young fish apparently spend one year in the outlet stream. The female fish mature between the ages of 2—4 and the males between 1—3. The mean number of eggs per female, plus or minus two standard deviations was 944± 393.29. A multiple regression analysis revealed that body length affected the number of eggs produced, 2.5 times as much as egg diameter. Recommendations were made, due to the probable effects of competition, that cutthroat trout be kept in pure culture populations. It was further suggested that cutthroat trout numbers be maintained in view of the severe reduction and almost extinction of the species in other areas.

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