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UBC Theses and Dissertations

The rearing and feeding ecology of juvenile rainbow trout from a large lake-fed river Irvine, James Richard


Juvenile rainbow trout (Salmo gairdneri Richardson) from the Lardeau River in southeastern British Columbia were studied in both their natural environment and stream tanks. In the river, highest densities of recently emerged trout occurred in areas with overhanging cover, shallow depth and minimal current. Older, underyearling trout were generally found in regions with smaller bottom particle size than yearlings; both age classes avoided fast current areas. Young trout migrated from the Lardeau River to Kootenay Lake during spring and summer. Except during these seasons trout were larger and more abundant in the upper versus the lower river; this was probably a result of better rearing habitat and higher biological productivity in the upper river. Trout fed almost exclusively on drifting organisms. Lake origin drift was an important food to riverine trout during summer; kokanee (Oncorhynchus nerka) eggs and fry were significant during fall and spring respectively. In stream tanks, where it was possible to manipulate prey populations, live prey were consumed significantly more than the same species when dead, suggesting that prey body movement was an important prey characteristic. In both the field and stream tanks, trout consumed prey within a discrete size range with larger fry generally consuming bigger prey than smaller fry. Further work is suggested which would improve our understanding of the feeding ecology of stream rearing trout.

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