能登半島東岸海域で漁獲されたブリ0歳魚のふ化日組成とその季節変化

抄録

Hatch dates of age-0 yellowtail Seriola quinqueradiata collected by set-nets in the eastern coastal area around the Noto Peninsula in the Sea of Japan between 2005 and 2007 were determined using the otolith daily growth increments. Hatch dates of 1146 individuals in total (range of 96-448 mm in fork length) were estimated by subtracting the number of otolith daily increments from the sampling dates. Estimated hatch dates of the age-0 fish samples indicated a protracted spawning season from late January to mid August. Then hatch month distributions of the recruitment in the whole fishing season were calculated by weighting the total catch by the number of age-0 fish from the set-net fishery in this area. Results showed that 57.7-69.5% of fishes were hatched during the period from March to April in every survey year. This suggests that age-0 fishes caught in the eastern coastal area of the Noto Peninsula mostly originated from the shelf break region of the East China Sea, the main spawning ground of yellowtail. On the other hand, hatch month distributions shifted later in progressive catching periods originating from other spawning grounds. Furthermore, age-0 fishes that hatched from March to April were hardly found in the coastal waters around the Noto Peninsula after December, and may migrate to other areas.