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UBC Theses and Dissertations

Migration and survival of juvenile spring Chinook salmon and sockeye salmon determined by a large-scale telemetry array Rechisky, Erin Leanne


This thesis documents the use a large-scale acoustic telemetry array to track hatchery-reared salmon smolts during their seaward migration, presents estimates of early marine survival, and describes migration behaviour in the ocean of two species of Pacific salmon from the Columbia and Fraser River basins. In the Columbia River basin, it is hypothesized that seaward migrating Snake River spring Chinook salmon suffer from “delayed mortality” due to passage through eight hydropower dams or “differential delayed mortality” from transportation via barge around the dams. I tested these hypotheses by comparing survival of in-river migrating smolts from the Snake River basin to 1) a Yakima River population that migrated past only four dams and 2) a Snake River group that was transported around all dams. Early marine survival estimates of non-transported Snake and Yakima smolts from the mouth of the Columbia River to Vancouver Island (a 485 km, one month journey) was equal in both 2006 and 2008 (2007 estimates were not available), which contradicts the delayed mortality theory. Early marine survival for the transported groups was slightly higher than for the in-river migrants, again contradicting the differential delayed mortality theory. These measurements form the first direct experimental test of key theories concerning juvenile fish survival in the coastal ocean. Cultus Lake sockeye salmon are a genetically unique population from the Fraser River basin and are now endangered due to the very low return of adults in recent years. Mean survivorship of smolts (2004-7) from release to the northern Strait of Georgia ranged from 10-50%, while survivorship to the final sub-array in Queen Charlotte Strait ranged from 7-28%. Cultus Lake smolts displayed four migratory behaviours: northward migration to enter the Pacific Ocean via Queen Charlotte Strait; westward migration through the Strait of Juan de Fuca; migration into Howe Sound before continued the migration north; and migration upstream into Cultus Lake. These are the first direct observations of movement and survival for Fraser River sockeye salmon smolts. The availability of early marine survival data fills key knowledge gaps and as well as permitting direct testing of important salmon conservation hypotheses and rapid scientific advance.

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