Juvenile Salmonid Use of Reconnected Tidal Freshwater Wetlands in Grays River, Lower Columbia River Basin

• DOI: 10.1577/t09-082.1
• Publication Date: 2010-07-13T18:09:49Z
• Authors: G. Curtis Roegner; Earl W. Dawley; Micah Russell; Allan Whiting; David J. Teel
• Keywords: Chinook wind; Hatchery

Abstract Degraded wetland systems with impaired hydraulic connections have resulted in diminished habitat opportunity for salmonid fishes and other native flora fauna the Pacific Northwest. Many of these lost habitats were once intertidal freshwater marshes swamps. Restoration is effected part by reestablishing tidal processes that promote connectivity, a central goal restoring rearing juvenile salmon Oncorhynchus spp. In Grays River system Washington, we measured hydrologic changes from removal tide gates diked pastureland determined subsequent time series abundance size frequency marshes. Dike breaching caused an immediate return full semidiurnal fluctuations to pasturelands. Juvenile salmonids quickly expanded into this newly available used prey items presumably produced within Habitat use varied species life history stage. Fry chum O. keta migrated rapidly through system, whereas populations Chinook tshawytscha coho kisutch resided March at least July composed fry, fingerlings, (for salmon) yearlings. Based on date timing hatchery releases, concluded most sampled restored reference sites progeny natural spawners. However, presence adipose‐fin‐clipped indicated hatchery‐raised fish originating outside also habitat. Because extensive mixing stocks practices, genetic analyses did not provide additional insight origins but reveal out‐migrating juveniles admixed population lower Columbia ancestry nonindigenous Rogue stock. wetlands estuary will improve overall ecosystem connectivity reduce fragmentation may therefore increase survival variety during migration.