Feeding Habits of Japanese Flounder (Paralichthys olivaceus) Larvae in the Western Part of Wakasa Bay, the Japan Sea.

Abstract

The feeding habits of Japanese flounder Paralichthys olivaceus larvae collected in the western part of Wakasa Bay were studied. Gut contents analysis was conducted on 393 larvae (from 2.3 to 7.9mm in notochord length) collected with an opening and closing bongo-type larva net (60cm diameter and 200μm mesh) from 12 May to 10 June 1986.The percentage of larvae with foods (feeding incidence) was low (25%) at the first feeding stage (stage A), in which the larvae were mainly fed on small copepod nauplii and invertebrate eggs. Feeding incidence increased with development and reached over 90% at stage C. Associated with the increase in feeding incidence, an increase in the size and size range of prey was observed. Main food items also shifted to Appendicularia (Oikopleura spp.) and/or large copepod nauplii (mainly Calanus sp.).The size of main prey organisms changed at each developmental stage. At stage B prey shifted from small copepod nauplii to the large Oikopleura spp. Japanese flounder larvae enlarged their prey gradually due to this prey selection.