Distribution and Growth of a Penaeid Shrimp Metapenaeopsis dalei in Suo-Nada, the Seto Inland Sea

Abstract

Population of a Penaeid shrimp Metapenaeopsis dalei in Suo-Nada, the Seto Inland Sea, was composed of the early and late cohorts. The carapace length of juveniles immediately after settlement exhibited a mode of 1.7mm, with a 95% confidence interval of 1.57 to 1.73mm. The late cohort settling in October was usually collected in shallower waters than the early cohort settling in September. The early cohort was suggested to migrate offshore with a decrease in temperature. In June, however, two cohorts seemed to spawn at the same area of 25m in depth. The highest value of growth rate was estimated at approximately 1.5mm/month from April to June, while no growth was observed below 13°C. The extremely low temperature also is considered to cause a large mortality to the late cohort.