Abstract
The aim of this article is to evaluate the effectiveness of scallop enhancement programs in Hokkaido. We analyzed the catch statistics from 1910 to 1993, and the number of seeds released from 1977 to 1993. The mean annual catch in weight in the last ten years (1984-1993) increased by 69 times in the Soya region, by 15 times in the Abashiri region, and by 6 times in the Nemuro region compared with that for the years before the commencement of stocking (1951-1973). Also, the coefficients of variation of annual catches by weight decreased considerably. The CVs between the years before stocking and the last ten years decreased from 1.41 to 0.38 in the Soya region, from 0.52 to 0.28 in the Abashiri region, and from 0.44 to 0.36 in the Nemuro region. We also analyzed the annuaI catch and seed release statistics by the local fishermen's associations. The recent increase in catches is supported by the seeds released and from increased reproduction from released seeds that have matured and added to the reproduction stock. The reproduction effect was markedly different between locations of the fishing grounds. As a whole, in Hokkaido the stock enhancement of scallop is economically successful, however, the yield for released seeds varies considerably among the fishermen's associations. Causes of the variation and release starategies were discussed.
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