Growth parameters of wild and selected strains of Atlantic salmon, Salmo salar, on two experimental diets

Atlantic salmon, Salmo salar, part from Penobscot (wild) and St. John River (selected) strains were cultured in 0.265 m(3) tanks filled with 20-30 ppt salinity well water and connected to a common bio-filter system. Because state and federal regulations require the culture of North American salmon by producers in Maine and the fact that most salmon currently cultured in the northeastern US and Atlantic Canada are from the St. John strain, the St. John River strain was chosen for inclusion in this study and compared to a local wild strain from the Penobscot River. Salmon part were stocked at approximately 5 kg/m(3) (100 fish/tank) and fed one of two experimental diets in a 2 x 2 factorial design with 4 tanks for each treatment. Each strain was fed a diet formulated to represent either a traditional high protein (THP), lower energy salmon diet (46% protein, 18% fat) or a newer high energy diet (NHE) (40% protein, 32% fat). Fish were anesthetized, counted and weighed at approximately 2 week intervals during a 23 week trial. Significant effects of strain on initial weight, final weight, specific growth rate, % feed consumed per day, and thermal growth coefficient were found. St. John strain salmon weighed more at the end of the trial (117.2 +/- 2.5 g) than Penobscot River salmon (71.2 +/- 2.5 g). There was a significant diet effect on final weight, specific growth rate, and thermal growth unit coefficient. There was no effect of strain, diet or interaction of these effects on feed conversion ratio. Diet had a significant effect on final weight of St. John River salmon (NHE 99.0 +/- 2.0 and THP 89.4 +/- 2.0 g), and no effect on the final weight of Penobscot strain salmon. Strain and diet also had significant effects on lipid composition and protein efficiency, while diet had a significant effect on protein retention. Strain differences accounted for 85.9% of the difference in final weight compared to 14.2% due to diet. Results indicate that St. John River salmon, which are commercially cultured and are being used in selective breeding programs, have superior growth rate compared to wild Penobscot River salmon. Published by Elsevier B.V.