2005 Volume 69 Issue 3 Pages 145-155
To clarify the early life history of pointhead flounder Cleisthenes pinetorum, spatial distribution, diel vertical migration and transportation of pelagic larvae were investigated in Funka Bay and its vicinity off Hokkaido Island in summer during 2001-2003. Larvae were mainly collected by simultaneously horizontal hauls with MTD closing nets in the transition water mass (32.4-33.6 in salinity) between Summer Funka Bay Water (<32.4) originating from Oyashio Water and Tsugaru Warm Water (>33.6 and>6°C). The younger stage larvae without yolk-sac (stage A and stage B) collected by MTD hauls occurred in the layers of 7.4-18.2°C, but not in those of 18.3-20.7°C. In day and night, stages A and B larvae were concentrated in the 20-40 m depth layers where copepod nauplii as the initial food item for them were less abundant than 1-10 m layers. A small scale of nocturnal ascent was observed in the advanced larvae inclusive of notochord flexion stage (stages C-F grouped), and they were collected in the 30-40 m and 20-40 m layers in day and night, respectively. Tidal vertical migration was not observed. Pelagic larvae would be transported from the offshore spawning ground to the nursery area in the bay with the transition water mass.
