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- Title
Seventy years of diminishing biocomplexity of California Central Valley hatchery steelhead, Oncorhynchus mykiss.
- Authors
Huber, Eric R.; Ryan, Rachael E.; Johnson, Rachel C.; Sturrock, Anna M.; Lusardi, Robert A.; Carlson, Stephanie M.
- Abstract
The California Central Valley steelhead (Oncorhynchus mykiss) has declined precipitously since Euro-American colonization and has been listed as threatened under the United States Endangered Species Act since 1998. Hatchery-origin fish now dominate the population, and hatchery management is a key listing factor. However, scant release metric information is available. We compiled a time series of O. mykiss hatchery release data for all four Central Valley hatcheries releasing O. mykiss between 1948 and 2017. The biocomplexity of released fish has declined since the early 1980s. Individuals have been released at increasingly similar numbers, biomass, body sizes, times, and locations over time. Moreover, yearling fish have been released at larger sizes, leading to the near-exclusive release of age-1 smolts in February and March since the late 1990s and early 2000s. Pervasive reductions in release portfolios have likely occurred for other hatchery-supported Pacific salmonid stocks throughout the Pacific Rim region. In an increasingly variable environment, such reductions in intraspecific diversity could significantly affect population stability and resilience.
- Subjects
PACIFIC Area; CENTRAL Valley (Calif. : Valley); FISH declines; RAINBOW trout; TIME series analysis; BODY size; DATA release; BIOCOMPLEXITY; BIOMASS; HATCHERY fishes
- Publication
Canadian Journal of Fisheries & Aquatic Sciences, 2024, Vol 81, Issue 4, p355
- ISSN
0706-652X
- Publication type
Article
- DOI
10.1139/cjfas-2023-0077