The Occurrence of Pelagic Larvae of the Japanese Flounder in the Yatsushiro Sea and Adjacent Waters, Japan.

Abstract

The seasonal and geographical occurrences of pelagic larvae of the Japanese flounder Paralichthys olivaceus in the Yatsushiro Sea (an inlet of 1,200km2) and neighboring waters in Kyushu were studied in the years 1989-1991. The larvae occurred from January to May, with a peak in March and April. The larvae were more abundant in intermediate and bottom layers than in the surface layer. Geographical occurrences of the larvae and patterns of the tidal currents suggested that the spawning of the fish in the inlet is insignificant and that the larvae of the pelagic stages migrate into the inlet mostly through the Nagashima Straits. Some sixty to seventy tons of the Japanese flounder Paralichthys olivaceus have been caught annually in the Yatsushiro Sea, Kumamoto Prefecture over the recent five years.1) Although it has been speculated that the fish might spawn in the central and southern parts of this inlet,2) only two pelagic larvae of the fish have ever been collected there.