Spatiotemporal occurrence and feeding habits of tonguefish, Cynoglossus lighti Norman, 1925, larvae in Ariake Bay, Japan

Spatiotemporal occurrence and feeding habits of tonguefish (Cynoglossus lighti Norman, 1925) larvae were investigated in an offshore area (>5m in depth) of the inner part of Ariake Bay, Japan. All specimens were symmetric, free-swimming larvae. Although their seasonal abundance and distribution in the study site varied from year to year, spawning started in June and the larval abundance was high in August and September with a wide distribution in the inner part of the bay. Both present and previous study results strongly suggest that larvae may settle primarily in the estuary and near-shore areas of Ariake Bay after their wide distribution in the offshore area of the bay during the free-swimming stage. Larvae showed a clear feeding rhythm in which they fed on prey mainly during the daytime. Larvae fed exclusively on copepods, and identified prey were mostly Paracalanidae (mainly Parvocalanus crassirostris), Microsetella norvegica, and Oithona davisae. Pre-metamorphosis larvae fed primarily on Paracalanidae and O.davisae, whereas O.davisae formed a smaller proportion of the early-metamorphosis diet. In early metamorphoses, larvae fed preferentially on Paracalanidae and M.norvegica.