Tuesday, May 27, 2008 - 10:45 AM
154

The influence of juvenile growth and migration patterns on smolt-to-adult survival of John Day River, Oregon, steelhead

Ian A. Tattam1, James R. Ruzycki2, Wayne H. Wilson2, Hiram W. Li3, and Guillermo R. Giannico3. (1) Oregon State University, Oregon Cooperative Fishery Research Unit, 104 Nash Hall, Corvallis, OR 97331, (2) Oregon Department of Fish and Wildlife, La Grande, OR, (3) Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, OR 97331

Juvenile steelhead in the John Day River basin exhibit a variety of migration patterns.  Migration patterns in freshwater ultimately influence the size and time at which juveniles enter saltwater.  A key difference in freshwater migration is the tradeoff between fall and spring emigration from natal streams.  We studied migration patterns in the South Fork John Day River from 2003-2005.  Our objectives were to a) determine potential environmental influences on fall emigration, b) determine spatial distribution of fall emigrants, c) compare smolt migration into the Columbia estuary of juveniles leaving natal streams in fall versus spring, and d) compare smolt-to-adult survival of steelhead with different juvenile migration patterns.  We found that biotic variables, such as growth rate, influenced fall emigration more than abiotic variables.  Juvenile steelhead which migrated to the Mainstem John Day during fall primarily aggregated in one reach with groundwater influence.  Smolt movement into the estuary was earlier for fall emigrants than spring emigrants.  Smolt-to-adult survival differed between migration patterns and years.  Results suggest that neither migration strategy has an advantage in adult recruitment during all years, thus, maintaining both strategies is key to sustaining viable stocks.  


Web Page: steelhead, ecology, John Day River

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