1Graduate School of Fisheries Sciences, 2T/S Ushio-maru Faculty of Fisheries, Hokkaido University, Hakodate, Hokkaido 041-8611, Japan
The spatial distribution of brown sole Pseudopleuronectes herzensteini eggs and larvae, and their food organisms were examined to elucidate the early life history of this species in Mutsu Bay. In April 1990-1997, pelagic larvae were widely distributed in the bay. Vertical distributions of eggs and larvae were investigated at two sampling stations in the bay from late February to late June in 1999-2001. Eggs of early, middle, and late stages occurred mainly in 30-40, 10-20, and 1-20 m layers, respectively. Yolk-sac larvae (stages A-B) occurred chiefly in the 20-40 m layer. The layer of abundant preflexion larvae (stages C-D) was slightly deeper (mainly 20 m depth) than that of copepod nauplii (10-20 m layer) as larval initial food. Larval concentration at 20 m depth may play some role in avoiding transportation to a shallow area unsuitable for settlement. Because the weighted-mean-depths of relatively larger larvae (flexion or postflexion larvae, stages E-G) were deeper (≥24 m) than those of stages C-D larvae (20-22 m), larvae would ontogenetically migrate for settlement.