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Abstract: We investigated differences in the timing of seaward migration among hatchery reared progeny of first and third generation captive brood and wild Shiribetsu River adult masu salmon released into the Furuu River of south-western Hokkaido in Japan, and naturally occurring wild masu salmon. After only three generations of domestication, captive brood smolts migrated downstream later than the hatchery reared progeny of wild fish of the same ancestry and of native Furuu wild smolts. In addition, there were sometimes significant differences in the timing of smolt migration between the Furuu River wild smolts and the smolts from the hatchery reared progeny of Shiribetsu River wild fish that suggests that there may also be important inter-river differences timing of smolt migration. We caution managers against using captive brood stocks that are more than two generations removed from the wild to avoid the development of potentially negative traits such as delayed seaward migration that may reduce salmon fitness and survival. We also caution managers against the transfer of fish between different river systems where the maintenance of natural self sustaining populations is important. [Copyright &y& Elsevier]

The relation between the density of fish and parameters such as body weight, condition factor and the hepatic triglyceride (TG) content of masu salmon Oncorhynchus masou juveniles after release into a natural stream were studied. Hatchery-reared juveniles of different sizes and numbers were released in May 1999, 2000 and 2001, and investigations were carried out from July to September each year. The density of fish was relatively high in 1999, when juveniles of the largest size and number were released, but then continued to decrease during the investigation. The hepatic TG content remained considerably low in 1999, and there was a significant negative correlation between the density of fish and the hepatic TG content of the juveniles caught over three years. The initial fish size and number at release as well as the nutritional condition of the juveniles may affect the density of fish after release. [ABSTRACT FROM AUTHOR]

Recreational fishing for masu salmon Oncorhynchus masou has recently become popular in coastal areas of south-western Hokkaido, including the Iburi district. We sampled recreational party boats in the Iburi district in the winters of 1998–1999 and 1999–2000. Daily numbers of anglers and catches of masu salmon were provided by the captains of the fishing boats. On average, anglers caught approximately four masu salmon per day each year, and peak catches occurred from late January to early February. Estimated numbers (standard errors in parentheses) of masu salmon caught by recreational anglers in the Iburi district were 66 844 (11 685) in 1998–1999 and 57 454 (6559) in 1999–2000, equivalent to 12–13% of the total annual commercial catches of masu salmon in Hokkaido. High recreational catches illustrate the importance of evaluating this fishery in the assessment and management of masu salmon in Hokkaido. [ABSTRACT FROM AUTHOR]