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Size-Dependent Smolt Yield and Overwinter Survival of Hatchery-Reared Masu Salmon Released in Fall

2003; Wiley; Volume: 23; Issue: 1 Linguagem: Inglês

10.1577/1548-8675(2003)023 2.0.co;2

1548-8675

Yasuyuki Miyakoshi, Hirofumi Hayano, Makoto Fujiwara, Mitsuhiro Nagata, James R. Irvine,

Fish Biology and Ecology Studies

To increase commercial marine catches of masu salmon Oncorhynchus masou in northern Japan, hatchery-reared juveniles are stocked at several life stages. To minimize mortality from freshwater angling, fish are often stocked in the fall when the fishing season is almost finished. In the fall of 1994–1998, we experimentally stocked hatchery-reared age-0 masu salmon (mean weights, 4.1–13.9 g) in the Masuhoro River of northern Japan. Mark–recapture experiments were conducted to estimate the numbers of hatchery-origin masu salmon smolts in the spring. Numbers of masu salmon parr in the river were estimated in July 1998–1999 when the smolt runs were almost finished. The proportion of fish smolting at age 1 (2.2–15.7%) was positively correlated with mean weight at release. Overwinter survival (9.0–17.0%) was also correlated with fish weight at release. Our study showed that size at release is an important factor when stocking age-0 masu salmon in the fall to maximize the number of smolts produced and thereby support marine fisheries.