Spawning pattern of the Japanese sardine Sardmops melanostictus off southern Kyushu and Shikoku southwestern Japan

Abstract

Distnbut~on, maturation and spawning of Japanese sardine Sardinops melanostictus in relation to the Kuroshio current are reported from an investigation off southern Kyushu and Shikoku, southwestern Japan, during the 1991 spawning season. Data were obtained from hydroacoustic surveys, measurement of gonadosomatic index and histological examination of oocyte maturity stage. Sardine shoals were distributed in both the coastal and the Kuroshio regions, but the maturity data showed a difference in spawning activity between the regions. Spawning activity was higher in the Kuroshio region than in the inshore region Spawning was concentrated within a short period of about 10 d in early March, although detectable In February and March Sardlne shoals did not occur In the Kuroshio region, except in early March. It was suggested that sardine were aggregated In inshore regions before spawnlng and that most of them moved offshore into the Kuroshio region to spawn and returned inshore after spawning.