THE INFLUENCE OF ENVIRONMENTAL-FACTORS ON EARLY-LIFE HISTORY PATTERNSOF FLOUNDERS

The near-shore migration and settlement phases of Japanese and America n flounders of the genus Paralichthys are compared and discussed relat ive to differences in coastal environments. Field sampling was conduct ed in Wakasa Bay, Kyoto Prefecture, Japan, where the shelf is narrow, estuarine habitat limited and tidal range slight, and in Onslow Bay, N orth Carolina, USA, where the shelf is broad, estuarine habitat extens ive and tide relatively strong. Distribution of larvae and juveniles s uggests Japanese flounder spawn in close proximity to nursery grounds relative to flounder in Onslow Bay. Sampling of planktonic and benthic flounder just seaward of nursery grounds resulted in capture of a wid e range of developmental stages in Wakasa Bay (early planktonic to juv enile), but was limited to metamorphosing larvae in Onslow Bay. Vertic al distribution of larvae during the night also differed between the B ays. At night most larvae in Wakasa Bay remained near the bottom regar dless of tidal stage. In contrast, larvae in Onslow Bay exhibited sele ctive tidal stream transport. Laboratory experiments conducted to exam ine the behaviour of recently captured wild and laboratory-reared larv ae indicated that wild flounder from Onslow Bay had an endogenous rhyt hm of activity that corresponded to the tide at the time of capture. I n contrast, wild flounder from Wakasa Bay and laboratory-reared larvae showed no distinct activity pattern. These results suggest that physi cal characteristics of the environment influence the early life histor y patterns of flounders by modifying behaviour of migrating larvae. (C ) 1998 Elsevier Science B.V. All rights reserved.