Abstract
To determine the nursery grounds and process of recruitment to adult stock, pelagic larvae, post-settlement juveniles and young fish of the pointhead flounder Hippoglossoides pinetorum, samples were collected in Ishikari Bay and the Rumoi coast, Hokkaido from 1991 to 1994. Spawning may continue from late May to mid September with the peak between July and August. However, since pelagic larvae were caught only from late July to early September in the present study, it was assumed that the restricted cohort recruited to post-settlement juvenile stage. Newly settled juveniles occurred in Ishikari Bay in September and in the Rumoi coast in late August and were mainly distributed at depths of 30-69 m. The habitat of 1-year-old and older flounder was deeper than that of 0-year-old flounder in autumn. Post-settlement juveniles gradually migrate to shallow areas during winter and their main habitats were at a depth range of 20-30 m in May. Although 1- and 2-year-old flounder were caught in the area of 20-40 m depths in June, few 3-year-old or older flounder were sampled by beam trawl. The same phenomena were recognized from the re-analyzed data of the otter trawl surveys in 1988. The pointhead flounder mainly occurred in the shallow water of the continental shelf until 2 years old and shifted their habitat to deeper areas (the upper area of the continental shelf) by 3 years old in Ishikari Bay and the surrounding area.
