Hatchery cultivation of Pacific oyster juveniles using algae produced in outdoor bloom-tanks

Algae were bloomed as batch cultures by adding fertilizers to natural seawa ter in 500 outdoor tanks, from mid-June to mid-August, over a period of 2 y . In the first year of experiments the bloomed algae were fed to Pacific oy ster (Crassostrea gigas Thunberg) juveniles at a range of rations from 0.06 to 1.63 g (organic weight of algae) g(-1) Give weight of spat) week(-1). A t rations of 0.5 g g(-1) week(-1) or higher, growth rates of juveniles were similar (mean, 97%) to those fed a control diet of intensively cultured al gae (Tetraselmis suecica Kylin) Butch and Chaetoceros calcitrans (Paulsen) Takano at a ration of 0.3 g g(-1) week(-1)). In the second year, the bloome d algae were fed at a ration of 0.5 g g(-1) week(-1) throughout all the exp eriments, and gave growth rates of 70-98% (mean, 85.6%), compared with the control diet. The proportion (by weight) of the diet consumed by the juveni les was about 70% for the control diet and 78% for the bloomed algae. Total lipid and essential fatty acid content of the bloomed algae were similar a nd total carbohydrate content was lower, when compared with typical publish ed values for intensively cultured algae food species.