Food Density and Rate of Feeding Larvae of Anchovy and Sardine in Patchy Distribution

Abstract

The feeding conditions of larvae of anchovy and sardine in patchy distribution were surveyed in order to know the mechanisms of larval survival in the sea. The larvae and plankters were continuously collected crossing their patches at sea surface (the length of one transect segment was 0.75-3 km). The patches of larvae and plankters detected were caused by oceanographic structure (i.e., front and upwelling) and were transported with eddy generated behind island by ocean current. The guts of the larvae collected were examined under microscope in order to know “feeding” or “non-feeding”, and the rate of feeding larvae in each segment was calculated. The rate of feeding larvae did not show any recognizable relationship with the density of their food organisms of each segment. The rate of feeding larvae was inversely correlated to the density of larvae of each segment. The rate of feeding larvae over 20 mm is high and under 5 mm extremely low. From these results, it is considered that the micro-patch of food organisms and the passing speed of food organisms in the visual field of larva, which is caused by turbulence of water, are possibly important in the larval feeding. © 1988, The Japanese Society of Fisheries Science. All rights reserved.