Submitted to: Aquaculture Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2012
Publication Date: 2/20/2012
Citation: Ju, Z., Forster, I., Dominy, W., Smiley, S., Bechtel, P.J. 2012. Evaluation of skate meal and sablefish viscera meal as fish meal replacement in diets for Pacific threadfin (Polydactylus saxfilis). Aquaculture Research. 2012:1-9. Interpretive Summary: Pacific threadfin, known in Hawaii as moi, are a popular seafood first cultured in significant quantities at the Oceanic Institute, and are now cultured in sea cages off the coast of Hawaii. The feed used in commercial production of these carnivorous finfish is based on fishmeal. There is interest in seeking alternative protein and oil ingredients for dietary replacements of fishmeal. The objectives of this research were to investigate the nutritional values of dried meals made from Alaskan skates and black cod viscera and to ascertain their suitability as replacements for commercial fishmeal in diets for Pacific threadfin. The skate meal made in this study is rich in protein and has a balanced essential AA profile relative to Pacific threadfin muscle. Skate meal can fully replace the commercial fishmeal in Pacific threadfin diets without adverse effect on growth performance. The black cod viscera meal had moderate protein content, but a high lipid content. At 50% replacement of pollock meal protein, BCVM did not support growth equal to that of pollock meal and therefore would not be cost effective when used as a substitute major protein ingredient in Pacific threadfin diets. The replacement of the commercial fishmeal by the skate meal did not affect the composition of Pacific threadfin fillets in this study. The replacement of the fishmeal by black cod viscera meal resulted in increased amounts of the long chain omega-3 fatty acids DHA and EPA in the Pacific threadfin fillets.
Technical Abstract: The objectives of this study were to investigate the nutritional value of skate meal (SM) and black cod viscera meal (BCVM) from Alaska and to ascertain their suitability as replacements for commercial pollock fishmeal in diets for Pacific threadfin (Polydactylus sexfilis). Test diets were made by replacing 50% or 100% of the fishmeal in the control diet with SM or BCVM on an isonitrogenous basis. The test diets (including a commercial feed) were randomly allocated to 4 replicated tanks with eight juvenile fish (9.7 g) per tank in an indoor culture system. After six weeks, Pacific threadfin fed SM-50% and -100% substituted diets exhibited similar weight gains (374%; 369%) and feed conversion ratios (FCR; 1.29; 1.27) as those fed the control diet (345%; 1.30). In contrast, Pacific threadfin fed the BCVM-50% substituted diet exhibited a considerably lower weight gain (112%) and higher FCR (2.16) than the control diets (P<0.01). The fish fed the control diet and SM substituted diets also achieved significantly higher (P<0.05) weight gain than those fed the commercial feed (288%). In conclusion, SM can fully replace the commercial fishmeal in Pacific threadfin diet without adversely effecting growth performance.