Iwate Fisheries Technology Center, Kamaishi, Iwate 026-0001, Japan
Stock sizes of wild and hatchery-reared flounder Paralichthys olivaceus in the coastal waters off Iwate Prefecture, Pacific coast of northern Honshu, Japan were estimated using VPA from 1990 to 2004. Biomass of wild stock fluctuated between 65 tons and 252 tons, with a continuous increase up to 200 tons from 1994 to 1997 and a continuous decrease after 2002. Biomass of hatchery-reared stock fluctuated between 8 tons and 63 tons, and the current level remained relatively low although a large number of hatchery-reared fishes over a million individuals have been released annually since 2001. The survival rate of hatchery-reared fish might be related to the released number because a negative correlation was represented between them. In wild fish, recruits increased in 1996, 1999 and 2000, but recently decreased to the lowest level. In the present waters, the recruits might be influenced by the coastal water temperature dominated by Tsugaru Warm Current during the pelagic larval period because its level was significantly correlated to spawning success (RPS), that was significantly correlated to the water temperature at 50 m depth in the most coastal region off northern Iwate in July.