Abstract

In order to obtain the basic information for seedling production of the scallop, Patinopecten yessoensis, the egg development and larva growth were investigated at different conditions such as water temperature, salinity and phytoplankton. Eggs were demersal isolated eggs, which averaged 77.3<TEX>${\pm}$</TEX>2.7<TEX>$\mu\textrm{m}$</TEX> in diameter after spawning. The fertilized eggs developed to D-shaped larva of shell length 117.5<TEX>${\pm}$</TEX>3.8<TEX>$\mu\textrm{m}$</TEX> after 60 hours at 15<TEX>$^{\circ}C$</TEX>. The range of water temperature and salinity during egg development were 10-20<TEX>$^{\circ}C$</TEX> and 28-34 ppt, respectively. The time of egg development was shorter with higher water temperature. After 10 days of spawning, D-shaped larva reached 160 <TEX>$\mu\textrm{m}$</TEX> in shell length, and after 25 days became full-grown larva 250 <TEX>$\mu\textrm{m}$</TEX> in shell length, in which could be observed eye spots. The relative growth formula between shell length (SL) and shell height (SH) was SH = 1.0425SL-27.731 (r<TEX>$^2$</TEX>= 0.9749) during the entire larva period. In regard to water temperature, growth and survival rates of larvae were good at 16<TEX>$^{\circ}C$</TEX>. Lower growth and survival rates were observed at 12<TEX>$^{\circ}C$</TEX> and 20<TEX>$^{\circ}C$</TEX> than that at 16<TEX>$^{\circ}C$</TEX>. When larvae were fed mixed phytoplankters, such as isochrysis galbana, Pavlova lutheri and Chaetoceros calcitrans, their growth and survival rates were the highest among groups.