Abstract
During 1999, the Idaho Department of Fish and Game (IDFG) continued developing techniques for the captive rearing of chinook salmon Oncorhynchus tshawytscha. Techniques under development included protocols for rearing juveniles in freshwater and saltwater hatchery environments, and fieldwork to collect brood year 1998 and 1999 juveniles and eggs and to investigate the ability of these fish to spawn naturally. Fish collected as juveniles were held for a short time at the Sawtooth Fish Hatchery and later transferred to the Eagle Fish Hatchery for rearing. Eyed-eggs were transferred immediately to the Eagle Fish Hatchery where they were disinfected and reared by family groups. When fish from either collection method reached approximately 60 mm, they were PIT tagged and reared separately by brood year and source stream. Sixteen different groups were in culture at IDFG facilities in 1999. Hatchery spawning activities of captive-reared chinook salmon produced eyed-eggs for outplanting in streamside incubation chambers in the West Fork Yankee Fork Salmon River (N=2,297) and the East Fork Salmon River (N=1,038). Additionally, a number of these eggs were maintained at the Eagle Fish Hatchery to ensure adequate brood year 1999 representation from these systems, and produced 279 and 87 juveniles from the West Forkmore » Yankee Fork and East Fork Salmon River, respectively. Eyed-eggs were not collected from the West Fork Yankee Fork due to low adult escapement. Brood year 1998 juveniles were collected from the Lemhi River (N=191), West Fork Yankee Fork Salmon River (N=229), and East Fork Salmon River (N=185). Additionally, brood year 1999 eyed-eggs were collected from the Lemhi River (N=264) and East Fork Salmon River (N=143). Sixty-two and seven maturing adults were released into Bear Valley Creek (Lemhi River system) and the East Fork Salmon River, respectively, for spawning evaluation in 1999. Nine female carcasses from Bear Valley Creek were examined for egg retention, and of these five were spawned out, one was partially spawned, and three died before depositing eggs. However, much of the spawning related behavior observed involved female chinook salmon paired with male bull trout Salvelinus confluentus. Two female carcasses from the East Fork Salmon River were recovered and examined for egg retention. One of these had spawned and one had not.« less
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