Effective Population Size in Winter‐Run Chinook Salmon

P. W. Hedrick, D. Hedgecock, S. Hamelberg

Research output: Contribution to journalArticlepeer-review

53 Scopus citations


Winter‐run chinook salmon from the Sacramento River, California, is federally listed as endangered. Since 1989 there has been aprogram to augment the natural population by capturing adults, artificially spawning them, raising tine young and releasing the smolt. Here we estimate the effective population size of these captive‐raised fish, the natural run, and the combination of both groups over the three‐year period from 1991 to 1993. We find that the most appropriate estimate of the effective population size of the captive‐raised progeny is a variance estimate of effective population size standardized so that the number of released smolts returning to spawn was the same as the number of spawners used to produce the smolts originally. We have generated 10,000 random samples to simulate returns from these released progeny. The estimates of the effective population sizes in 1991, 1992, and 1993 were only 7.02, 19.07, and 7.74, respectively. We then determined limits on the effective population size of the natural run based on 0.1 and 0.333 of the run‐size estimates. Using estimates of the captive proportion of the run, the minimum estimates of the effective population size of the overall run for the three years were 21.9, 127.3, and 39.0, and the maximum estimates were 61.6, 401.0, and 108.7. It does not appear that the hatchery program has reduced the overall effective population size. The run sizes in each year are extremely low, however, and it is possible that fish will be lost from this run in one of the years in the immediate future, making reestablishment of a healthy run even more difficult.

Original languageEnglish (US)
Pages (from-to)615-624
Number of pages10
JournalConservation Biology
Issue number3
StatePublished - Jun 1995

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology
  • Nature and Landscape Conservation


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