UBC Theses and Dissertations

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UBC Theses and Dissertations

Genetic and environmental mechanisms controlling the lakeward migration of young rainbow trout (Salmo gairdneri) from outlet and inlet rearing streams Kelso, Bryan William


The upstream-downstream response to water current exhibited by rainbow trout fry in inlet and outlet streams of Loon and Pennask Lake stream systems was studied in experimental laboratory performance channels. Analysis of diallel tables, developed by crossing seven different inlet and outlet spawning stocks from the two stream systems, demonstrates additive genetic differences between the two stocks with respect to current response. Tests performed in daylight showed a net upstream movement for all stocks, but far greater for outlet compared to inlet fry. At night, inlet fry showed a very strong downstream movement while outlet fry showed very little movement, similar to their behavior in the field. Further analysis of the diallel table, when all the stocks were tested at three temperatures (low: 5C, medium: I0C, high: 17.5C), showed that temperature both in daylight and darkness tended only to change the degree of upstream or downstream movement of the fish, rather than the direction of movement. In daylight, upstream movement for all stocks was greatest at low temperature and least at high temperature. In darkness the greatest downstream response was at high temperature. However, at high temperature outlet fry moved farthest upstream in daylight while in darkness inlet fry moved farthest downstream. Other possible controlling mechanisms (sudden temperature rises in the outlet creek, water source, abundance of food, genetic differences in liver lactate dehydrogenase) are considered. The diallel analysis suggests that there are genetic differences in the current response between the inlet and outlet stocks and that water temperature plays only a minor role in the migration of rainbow trout fry to the lake.

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