|Document Type:||Journal Article|
|Title:||Variation in minijack rate among Columbia River Basin Chinook salmon hatchery populations|
|Author:||D. L. Harstad, Donald A. Larsen, Brian R. Beckman|
|Journal:||Transactions of the American Fisheries Society|
|Keywords:||minijacks,Chinook salmon,hatchery,life history,|
In Chinook salmon (Oncorhynchus tshawytscha), age of maturation ranges from age-1 (microjack), -2 (minijack), -3 (jack), to -4 or -5 (adult) years. The presence of age-2 minijacks has been noted in several experimental studies and documented for a few hatchery programs but a comprehensive survey of their occurrence in hatchery production programs has never been conducted. We measured minijack rates at several spring- and summer-run Chinook salmon hatchery programs throughout the Columbia River Basin among brood years 1999 through 2010. The hatcheries surveyed included both segregated (only hatchery-origin broodstock) and integrated (some natural-origin broodstock) programs. Minijacks were found in all programs monitored, and rates varied approximately tenfold across release groups ranging from 7.9 - 71.4% among males in spring Chinook salmon programs and 4.1 - 40.1% among males in summer Chinook salmon programs. There was a significant relationship between size at release and minijack rate in the integrated but not the segregated spring Chinook salmon programs. Minijack rates were significantly higher in the integrated programs compared to the segregated programs despite the fact that most of the integrated programs released smaller fish, suggesting that artificial selection for age at maturation has occurred in segregated programs.
|Theme:||Recovery, Rebuilding and Sustainability of Marine and Anadromous Species|
Maximize effectiveness and minimize impacts of artificial propagation in recovery, rebuilding and stock sustainability