若狭湾西部海域におけるタチウオの漁業生物学的研究 Ｖ 若狭湾西部海域におけるタチウオ卵・稚子魚の分布

Abstract

Horizontal and vertical distributions and transportation of the ribbon fish Trichiurus leprurus eggs and larvae were described, based upon the sampling data of multilayer horizontal tows from May to September, 1983 in the western Wakasa Bay. The ribbon fish eggs and larvae mainly distributed from the middle to deep layers in the offshore (120min depth) from May to September. From early to late developmental stage eggs distri-buted at the same layer, and when temperature and salinity discontinuities occurred at middle layers (Jul. -Sep.), peak densities of eggs were observed from the middle to deep layers, though the eggs occurred from surface to deep layer when temperature and salinity discontinuities dis-appeared (Jun.). Based upon the elapsed time in developments of the ribbon fish eggs and larvae and the velo-city of Tsushima Warm Current in summer, it was estimated that some of the late stage eggs and larvae of more than 7mm in total length occurred in the western Wakasa Bay were transported from far more than 40 and 60 nautical miles with axis of Tsushima Warm Current (far west of the Hyogo and Tottori offing), respectively. From monthly changes in horizontal and vertical profiles of the eggs and larvae distributions and total length compositions of the larvae between the offshore and inshore, it was suggested that an inshore transport process of the ribbon fish eggs and larvae occurred by current trans-portation and their own positive movement.