Age-structures and catch fluctuations of arabesque greenling (Pleurogrammus azonus) in the coastal area of southern Hokkaido, Japan

We investigated the age-structures and catch fluctuations of arabesque greenling (Pleurogrammus azonus) caught in principal fisheries of the coastal area of southern Hokkaido in order to understand the resource dynamics. The age-structures of the fish products from the south of Shiribeshi and coastal area around the Matsumae Peninsula included the newly recruited (1-year old) and adult cohorts (2-years and above). In the coastal area around the Kameda Peninsula, fish products consisted of immature fish that were 1-2- years old. The age-structure of the fish products from the Tsugaru Strait had a higher proportion of older fish than those from other areas. The trend of catch fluctuation has been declining since the 1990s in the Matsumae Peninsula area, in contrast to the Shiribeshi area, although the rate of annual catch in both these areas has changed in a similar pattern. The difference in the catch fluctuation trend between the Matsumae Peninsula and Shiribeshi areas may have been due to the unusual recruitment of the 1991-cohort because of a remarkable change in water temperature during the spawning season after 1990.