Complete replacement of fish meal (FM) and fish oil (FO) in the diets of carnivorous farmed fish will likely be required to meet the projected growth of the aquaculture industry in a sustainable way . A number of viable ingredient s have been found to replace FM, while suitable alternative s to FO have been more challenging to identify due to the essential long-chain omega-3 fatty acids that are missing from terrestrial alternatives. Schizochytrium sp . is a microalga that is high in docosahexaenoic acid (DHA) , one of the aforementioned omega-3 fatty acids that are required by fish and important for human nutrition . This study was conducted to determine the effects of microalga-enriched fish-free feeds on sablefish growth, condition, and fatty acid profile .
A 20-week feed study was conducted in a n outdoor tank array in Moss Landing, CA . Juvenile sablefish were distributed randomly in to 18 tanks (1000L) with 15 fish per tank (average weight ± SD, 333g ± 2.4g). Six diets were formulated to contain 45% protein and 15% lipid. Diet 1 contained standard levels of FM and FO. Diet 2 contained FO , but no FM. Diet 3 was completely FM and FO free, made with terrestrial ingredients only . Diets 4, 5, and 6 were FM and FO free, and contained increasing levels of the microalga, Schizochytrium sp. (dried whole cell biomass) , with flax oil making up the remaining lipid requirement. Treatments were assigned randomly to the tanks with three replicate s per treatment.
Preliminary results suggest that sable fish growth increases with increasing inclusion of Schizochytrium sp. and is not significantly different in performance to the control diet containing standard FM/FO concentration. Fatty acid profiles of the fish fillets indicate that sablefish are able to incorporate DHA from the dried whole-cell Schizochytrium sp. into their muscle tissue commensurate with DHA inclusion in the diets.