Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 4743
Title: Eliminating variation in age-at-spawning leads to genetic divergence within a single salmon population
Author: C. T. Smith, J. Baumsteiger, W. R. Ardren, Y. Defflaff, D. K. Hawkins, Donald M. Van Doornik
Publication Year: 2014
Journal: Journal of Fish and Wildlife Management
Volume: 6
Pages: 4-18
DOI: http://dx.doi.org/10.3996/122013-JFWM-086
Keywords: precocious males,jacks,population structure
Abstract:

Most coho salmon Oncorhynchus kisutch in Washington state spawn at 3 y of age, creating the potential for three temporal populations or “broodlines” at each spawning site. This is generally prevented by a portion of males in each site that mature and reproduce at 2 y of age, resulting in population structure in which the geographic component is stronger than the temporal component. The Quilcene National Fish Hatchery, located on Big Quilcene River in the Hood Canal region of Washington state, selected against late returning coho salmon by excluding all but the earliest returning fish from its broodstock for an unknown number of generations, and restricted gene flow among broodlines by excluding 2-y-old males for 27 generations. The resulting hatchery population exhibited three distinct broodlines that returned in alternating years: an “early” broodline that arrived 1 mo before the wild fish, a “late” broodline that arrived at the same time as the wild fish, and a “middle” broodline that arrived in between these two broodlines. We evaluated temporal and geographic components of population genetic structure in coho salmon from the Quilcene National Fish Hatchery and nine other sites from Puget Sound and the Strait of Juan de Fuca using 10 microsatellite loci. Genetic diversity at the Quilcene National Fish Hatchery was lowest in the early broodline and highest in the late broodline. Divergence among broodlines at the Quilcene National Fish Hatchery was greater than that observed at any other site, and was also greater than that observed between any of the sites. This apparent reversal of the relative magnitudes of temporal and geographic components for this species emphasizes the importance of variable age-at-maturity in shaping population genetic structure.

Theme: Recovery, Rebuilding and Sustainability of Marine and Anadromous Species
Foci: Maximize effectiveness and minimize impacts of artificial propagation in recovery, rebuilding and stock sustainability