Short-term occurrence and rapid growth of Spanish mackerel larvae in the central waters of the Seto Inland Sea, Japan

To investigate the early life history of Japanese Spanish mackerel Scomberomorus niphonius in the Seto Inland Sea, abundance, occurrence, feeding habits, and growth of larvae were examined from wild specimens collected in Hiuchi-nada in 1995 and 1996. In addition, Japanese Spanish mackerel were reared in the laboratory to determine the rate of otolith microstructual increment formation during early stages. Japanese Spanish mackerel in the central waters of the Seto Inland Sea appear to have evolved a reproductive strategy of short-term spawning rimed to correspond to the seasonal-peak abundance of their prey. Japanese Spanish mackerel laevae were almost exclusively piscivorous and their most important prey was Clupeiformes larvae with slender body form. Occurrence of Japanese Spanish mackerel eggs and larvae was restricted with a peak abundance in late May to early June, corresponding with a peak abundance of Clupeiformes larvae. Age estimation for 70 wild larvae and early juveniles revealed a mean growth rate of 1.03 mm/day between 4 and 20 days after hatching, which appears to be markedly higher than those from most of coastal marine fishes.