Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 7899
Title: The spawning success of early maturing resident hatchery Chinook salmon in a natural river system
Author: Michael J. Ford, T. N. Pearsons, A. R. Murdoch
Publication Year: 2015
Journal: Transactions of the American Fisheries Society
Volume: 144
Issue: 3
Pages: 539-548
Keywords: minijacks, parentage, Wenatchee River, early life history stages, hatchery and wild, Chinook salmon,

Hatchery propagation of spring Chinook Salmon Oncorhynchus tshawytscha has been shown to increase the proportion of males maturing as minijacks (age 2) or microjacks (age 1) relative to those proportions in wild populations.  However, little is known about the success of early maturing males when they spawn in the wild.  A captive broodstock program for spring Chinook Salmon in the White River (a tributary of the Wenatchee River, Washington) has a high rate of early male maturity.  We used genetic parentage analysis to evaluate the spawning success of anadromous males in comparison with inferred early maturing resident, hatchery–origin males that spawned naturally.  Based on samples of juvenile offspring (n D 1,007–1,368 fish/year) and a nearly complete sample of the potential anadromous parents, we found that during 2006–2009, 26–45% of the progeny did not have a male parent in the anadromous sample.  In contrast, 0–23% of the progeny did not have a female parent represented in the sample.  Using grandparentage analysis, we eliminated wild resident fish as a likely source of the unsampled male parents; thus, we concluded that those male parents were most likely early maturing resident fish that had been released from the captive broodstock program.  The inferred spawning success of the unsampled resident males was significantly lower than that of the anadromous males.  The typical mating pattern was for an anadromous female to produce about two–thirds of her offspring with one or two anadromous males and the remaining one-third with as many as 12 or more apparently resident males.  To our knowledge, this is the first study to present evidence of successful reproduction by early maturing resident, hatchery–origin Chinook Salmon in the wild.  The conservation implications of this finding are complex and will depend upon the genetic basis of early maturity and its causes in hatchery settings. 


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Theme: Recovery and rebuilding of marine and coastal species
Foci: Evaluate the effects of artificial propagation on recovery, rebuilding and sustainability of marine and anadromous species.