Larval dispersal and recruitment of Haliotis discus hannai and Tegula spp. on Miyagi coasts, Japan

Abstract

The spatial dispersal and vertical distribution of larvae of Haliotis discus hannai and Tegula spp. were examined in relation to storm events in Miyagi Prefecture, Japan, from 1983 to 1993. Epidemic spawning is induced by typhoons and minor storms. After typhoons, larvae are dispersed in coastal waters up to 3 km from shore to a depth of 30 m and later are advected toward the coast by onshore winds. After minor storms, larvae are locally dispersed close to shore. Larvae of H. discus hannai and Tegula spp. become vertically stratified and settle on the substratum at depths in accordance with the vertical depth range of their larvae. Strong settlements of H. discus hannai of up to 200 m^-2 were recorded around headlands, with average survival rates of about 13% per month in the first 2-3 months. The adaptive significance of dispersal over short and long distances is considered.