Piscivorous Habits of Spanish Mackerel Larvae in the Seto Inland Sea

Abstract

The stomach contents of 100 yolk-sac larvae and 376 larvae of Spanish mackerel collected in the Seto Inland Sea from 1981-1983 were examined. Standard lengths (SL) of prey animals were back-calculated from their body heights (BH). Late stage yolk-sac larvae with eye pigmentation had jaw teeth and gastric blind-sac, and some of them had already initiated feeding. Stomach contents of larvae consisted primarily of fish larvae, though invertebrate zooplanktons were observed in some early stage larvae. Main prey of Spanish mackerel larvae were larval Clupeiformes, 21% being Japanese anchovy (93% of identified Clupeiformes). The ratios of head length (HL), upper jaw length (UJL), and body height (BH) to SL of Spanish mackerel larvae increased as larval size increased until 11 mm SL, then remained constant. The back-calculated maximum size and the size range of Japanese anchovy larvae eaten by Spanish mackerel larvae increased until 12 mm SL. Spanish mackerel larvae larger than 12 mm SL fed on 8-12 mm SL Japanese anchovy larvae. The feeding incidence was high for early larval stages: 66, 84, and 92% in 4-5, 5-6, and 6-7 mm SL larvae, respectively. These results suggest that Spanish mackerel larvae collected in the Seto Inland Sea actively fed mainly on fish larvae from the first feeding stage.