Commercial harvest of hatchery-reared masu salmon Oncorhynchus masou estimated by a coast-wide sampling program in Hokkaido, northern Japan, and the two-stage sampling schemes of landings

Abstract

SUMMARY: This paper evaluates the stocking effectiveness of masu salmon Oncorhynchus masou in Hokkaido, northern Japan, through a coast‐wide two‐stage sampling survey of commercial landings. From January to June 1994–1996, commercial landings of masu salmon at 33–36 fish markets were sampled at 7–10 days intervals, and 60 866–72 124 fish were examined for marks indicated by fin clips. Based on the survey data, numbers of total and hatchery‐reared masu salmon landed were estimated. To examine the structure of the errors, stratification of fish markets was implemented on the basis of geography and magnitudes of landings, and the stratification improved accuracy and precision of the estimates. Accuracy of the estimated numbers of total fish was evaluated by being compared to the true numbers of masu salmon landings reported by fishermen’s cooperative associations. Estimates of total masu salmon landings were within ± 10% of the true numbers. The estimated recovery rates (± SE) for hatchery‐reared masu salmon smolts were variable ranging from 0.18 (± 0.06) to 3.50 (± 0.41)% among the stocked groups. An optimal sampling strategy was examined to obtain precise estimates for future studies.

Population Genetic Structure and Phylogeography of Masu Salmon (Oncorhynchus Masou Masou) Inferred from Mitochondrial and Microsatellite DNA Analyses

“…Although masu salmon is an important fisheries species, its commercial catch has decreased over the years (Miyakoshi et al, 2001(Miyakoshi et al, , 2004. Hatchery programs have been established to release fry artificially obtained from eggs of the limited spawning groups, which will cause decreased genetic diversity of subsequent breeding groups, possibly affecting the genetic structure of natural breeding groups (Noguchi and Taniguchi, 2007).…”

Genetic differentiation between collections of hatchery and wild masu salmon (Oncorhynchus masou) inferred from mitochondrial and microsatellite DNA analyses

“…Therefore, the suggested genetic differentiation might be due to a reduction in the genetic diversity in the hatchery broodstocks, which can be regarded as an ongoing process. Hatchery programs of masu salmon implemented in Japan appear to be unsuccessful based on observations of declining commercial catches (Miyakoshi et al 2001(Miyakoshi et al , 2004. However, factors Table 1: filled circle, the Sea of Okhotsk coasts; filled square, the sea of Japan coasts; open square, Hatchery samples responsible for the poor results in masu salmon stock enhancement remain mostly unknown, making it difficult to improve on current hatchery programs.…”

“…However, commercial catch of masu salmon in Japan is gradually decreasing (Miyakoshi et al 2001(Miyakoshi et al , 2004, despite the long history of concerted efforts aimed at artificial propagation and stocking since the late 19th century (Mayama 1992).…”

A review of Pacific salmon hatchery programmes on Hokkaido Island, Japan

“…40% on average in the period 1971e2003. The contribution of hatchery fish to masu salmon catches was estimated to be 12e23% (Y. Miyakoshi, unpublished data), based on the tagging data presented in Miyakoshi et al (2001aMiyakoshi et al ( , b, 2004b.…”