Ecology and post-settlement survival of the ezo abalone, Haliotis discus hannai, on Miyagi coasts, Japan

摘要

Settlement and survival of the ezo abalone, Haliotis discus hannai were examined in near-shore habitats at exposed to sheltered sites on Miyagi coasts, Japan from 1996--1999. Larvae settled mainly in the boundary zone at 2-7 m depth according to site between shallower Eisenia forests and deeper crustose coralline flats at densities of approx 200-800/m~2. Growth rates were 30-40 #mu#m/day. Instantaneous natural mortality rates, M, in the first 55 days after settlement were 3.7-5.5/month. Sampling ofthe habitat during the week after settlement showed a 29-37 percent incidence of atrophied post-larvae of approx 500 #mu#m shell length indicative of starvation. Laboratory experiments suggested that post-larvae exhaust the natural food supply on crustose coralline algae in the first week after settlement and begin to starve at a size of approx 450-500 #mu#m in the absence of a suitable diatom diet. One-year-old juveniles were mainly found in the boundary zone but with increasing age juveniles moved into the shallower Eisenia forest where food algae is abundant.