Feeding, Growth, and Dispersal of Hatchery-reared Spotted Halibut Verasper variegatus Released in a Shallow Brackish Lagoon: Matsukawa-ura, Northeastern Fukushima, Japan

摘要

Post-release feeding, growth, and dispersal of hatchery-reared spotted halibut Verasper variegatus were investigated in a shallow brackish lagoon: Matsukawa-ura. In 2003 and 2004, totals of 27,900 and 53,217 seedlings respectively comprising three andfour sub-release cohorts (8.0-10.1 cm total length, TL) were released into central Matsukawa-ura during June 2003 and June-August 2004, respectively. Post-release 2-m beam-trawl surveys of five sampling stations revealed that the released seedlings mainly moved southward, started feeding quickly, and adapted to the released habitat about one week after release. Main food items of the seedlings <15 cm TL were mysids and gammarids, which (especially the former) were abundant near the release site. Catchper unit effort decreased quickly in all release cohorts. However, no seedling was detected from the guts of piscivorous fish species. The seedling growth rates were lower than that of wild juveniles, which suggests the necessity of production and release of high-quality seedlings with appropriate growth history in the hatchery. Age-1 seedlings were rarely collected in Matsukawa-ura, but they were caught in the outer ocean by gillnet and trawl fishing after June, indicating that many age-1 fish had emigrated to the outer ocean by summer.