Evaluating Schizochytrium Sp. As an Alternative Ingredient in Fish-Free Feeds for Sablefish (Anoplopoma Fimbria) Aquaculture

Alternative feeds for marine finfish aquaculture are critical for the sustainable expansionof the aquaculture industry. Fish that are farmed for human consumption are often carnivorous; therefore, the industry uses wild-caught forage fish as a primary ingredient in feeds in the form of fishmeal and fish oil. As the aquaculture industry grows, it is important to identify alternative feed ingredients with high omega-3 polyunsaturated fatty acid (PUFA) concentrations. This study was designed to test a microalga, Schizochytrium sp., as an alternative feed ingredient for sablefish (Anoplopoma fimbria) using six test diets. The first diet (+FM+FO) contained both fishmeal and fish oil. The second diet (-FM+FO) contained fish oil, but no fishmeal. The remaining four diets were completely fish-free. FF Flax had flax oil as the fish oil replacement. FF LowSc, FF ModSc, and FF HighSc contained a low, moderate, and high level of Schizochytrium sp. to replace fish oil, with flax oil content decreasing as the microalga increased. After a 20-week trial, sablefish growth was influenced by treatment, with the high microalga-inclusion diet (FF HighSc) performing similarly to the fish-ingredient controls. Fulton’s condition factor and some feed utilization metrics were also influenced by treatment. Fillet fatty acid profiles were similarly influenced by diet treatment, generally reflecting the fatty acid profiles of the feed. Total PUFAs were higher in the fishfree diets than in the controls. These results suggest Schizochytrium sp. can increase PUFA concentrations in fish fillets without compromising fish health and growth, making it a viable ingredient for alternative sablefish feeds