Seasonal and spatial variations in prey utilization and condition of a piscivorous flatfish Paralichthys olivaceus

We investigated the diet and somatic condition of 5129 individual Japanese flounder Paralichthys olivaceus, 20 to 92 cm in total length, in the Joban area along the Pacific coast of Japan (36 degrees 40' N to 38 degrees 00' N) from 2001 to 2007. Japanese flounder with food in their stomachs (1668 individuals) consumed chiefly fishes (92% of stomach contents by weight). Predominant prey species were Japanese anchovy Engraulis japonica (54% of fishes by weight) and Japanese sandlance Ammodytes personatus (22%). Japanese anchovy were consumed by Japanese flounder year round except in March and April, when the anchovy migrate from the Joban area. In March and April, Japanese flounder frequently consumed Japanese sandlance, but only in the northern part of the Joban area (37 degrees 20' N to 38 degrees 00' N); Japanese flounder did not feed on this species and had less content in their stomachs in the southern area (36 degrees 40' N to 37 degrees 20' N), where the sandlance is absent. Somatic and hepatosomatic conditions of Japanese flounder in the northern area were better than those in the southern area in March and April, suggesting that such spatial and seasonal hetero-geneities in prey availability affect the nutritional status of predators.