Oysters can grow very well in cold water if there is abundant, high-quality plankton.
Many estuaries in Alaska produce so much high-quality plankton during certain times of the year that Alaskan shellfish can match growth achieved by shellfish raised in warmer waters of the Pacific Northwest. Cold, clean water also reduces bacterial contamination, extending shelflife and assuring safety when eating cultured oysters, especially when eaten raw. Pacific oysters, grown in warm waters, reach sexual maturation during their second summer of life, causing them to become soft and a milky color. These characteristics make the oysters unmarketable. In Alaska, because cold water retards maturation, high-quality oysters are available year round.