Green-Water Rearing and Delayed Weaning Improve Growth and Survival of Summer Flounder

The advent of an aquaculture industry for summer flounder Paralichthys dentatus requires that optimal methods be identified for hatchery production. Two experiments were conducted to test strategies for larval rearing and for weaning newly metamorphosed juveniles from live to artificial diets. Rearing of larvae in ‘‘green water’’ (with algae added) resulted in better survival (76.1 6 6.5%) from days 5–42 after hatching than did rearing in ‘‘clear water’’ (no algae added; 27.8 6 13.6%), although no differences in growth were apparent. When fish were weaned from live feed beginning at day 45 versus day 57 by either a ‘‘gradual’’ method (7-d weaning period) or an ‘‘immediate’’ method (no weaning period), better survival and growth were obtained with fish weaned at the later age. For both agegroups, fish weaned by the gradual method exhibited better growth, but not better survival, than those weaned by the immediate method. With these data as examples, commercial hatcheries can conduct cost : benefit analyses of the different rearing methods