Studies on propagation of Ezo abalone, Haliotis discus hannai Ino-II. The appearance and growth of 0-year-old Ezo abalone.

Studies on the appearance and growth of 0-year-old Ezo abalone, were made from September 1974 to November 1975 in Toyoura, which were seed-transplanted grounds in south Hokkaido. The same studies were made from November 1976 to December 1977 in one part of Okushiri Island, which is the source of seed supply for Toyoura. In Toyura, 0-year-old abalones began to appear in November, and ceased to grow for five months since December. They acquired the first annulus on shells of 21 to 22mm in length. The viability of young abalones was quite low, probably owing to the low water temperature of 0 to 1°C in early March. In Okushiri Islang, young abalones born in that year were found in December, with 3.1 mm-long shells. They continued to grow by 2mmin length per month from June of the next year to December, and then stopped growing and acquired the first annulus on 16.8mm-long shells. In spite of the good water condition for abalone survival in winter, always above 3°C in temperature, the growth rate there was lower than in Binosaki, the poorest place in shell growth in Toyoura.