ABSTRACT
Most oyster culture in the world depends on the traditional “on-bottom” methods, but in Japan “off-bottom” culture methods have been developed and perfected and have been introduced to the world by many authors. The upper valve of Crassostrea gigas is flat and a little smaller than the lower, deeply cupped left valve. Outer shell form varies smooth to fluted, and ribs often radiate from the umbo. Morphological variation is great in this species. The shape of the shell varies with latitude, the southern oyster being smaller, rather oval, and more cupped. Normal development of eggs to metamorphosis is limited to a narrower temperature range than can be tolerated by early cleavage stages. The optimum salinity range for development of eggs to the straight-hinge stage depends on the salinity where their parents were grown. Japanese oyster larvae attach themselves to many of hard surfaces, including rocks, concrete, bamboo, wood, shells of other mollusks, plastics, tin cans, and rubber.
