Semi-natural rearing of coho salmon, Oncorhynchus kisutch (Walbaum), smolts, with an assessment of survival to the catch and escapement |
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Authors: | J H MUNDIE D E MOUNCE K S SIMPSON |
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Institution: | Department of Fisheries and Oceans, Biological Sciences Branch, Pacific Biological Station, Nanaimo, British Columbia, Canada |
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Abstract: | Abstract. To assess the merits of rearing coho salmon, Oncorhynchus kisutch (Walbaum), smolts semi-naturally, trials were made in which 17 groups of tagged smolts, from 4 brood years, were raised on a partially natural diet in a semi-natural habitat. Their subsequent survival, as determined from catch and escapement, was compared with that of four groups of smolts, from the same brood years, raised by a conventional hatchery method. The returns of the semi-natural fish proved lower than or similar to those of the hatchery fish, which attained a maximum survival to catch and escapement of 26%. The survival of the semi-natural fish showed no relation to their location in their linear rearing facility, nor to size of smolt (within a narrow range). Further trials showed that a month's delay in release of the semi-natural fish did not increase returns, contrary to a current predictive model. The distribution of the catches of both kinds of fish was broadly similar in the troll and sport fisheries. It is concludedthat semi-natural rearing of coho smolts is not superior to that of standard hatchery procedures, although it may be favoured for specific locations that lend themselves to this approach. |
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