Returns of Pen-Reared Steelhead from Riverine, Estuarine, and Marine Releases

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Abstract
Hatchery-reared steelhead (anadromous rainbow trout Oncorhynchus mykiss) were released as smolts in 1982 and 1983 at four locations in and near the Keogh River on northern Vancouver Island, British Columbia, to determine the effect of release location on adult return rate, Smolts were released at four sites simultaneously: 10 km upstream from the river mouth (10km site), 0.4 km upstream from the river mouth above a fish-counting fence (0.4-km site), in the tidal area below the fence (0.3 km upstream), and in the ocean about 1.6 km off the mouth of the river. Return rates were estimated by mark and recapture of adults and kelts at the counting fence 1–3 years later. Based on numbers released, the return rates of the 1982 groups were 7% for the 10-km site, 11% for the 0.4-km site, 10% for the tidal site, and 11% for the ocean site, The respective return rates of the 1983 groups were 3, 5, 7, and 5%. We suggest that failure to migrate, as well as predation, accounted for the lower return rates offis...

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