Phenotypic and Genetic Variation in Two North American Arctic Charr,Salvelinus alpinus,Stocks Cultured in a Recirculating Aquaculture System

Arctic charr, Salvelinus alpinus, were obtained as eggs from two North American sources, an eastern (Fraser River, Canada) and a western (Bristol Bay, Alaska, USA) stock. Fish were pit tagged (eastern , western ) and stocked communally into three replicated 7‐m³ tanks at a density of 7.6 ± 1.2 kg/m³. Each tank was supplied with 2 ppt salinity water from a recirculating biological filtration system. Fish were fed a commercial diet (48%P, 20%F) from automatic feeders. Fish were harvested approximately 24 mo after hatching at a final tank density of 56.2 ± 1.3 kg/m³. Mean daily water temperature was 10.4 C with a range of 5.9–12.6 C and mean dissolved oxygen was 12.6 mg/L with a range of 9.7 (91% of saturation) to 17.8 mg/L (149% of saturation). Individual fish were evaluated for total, carcass, and fillet weight, sex, stage of sexual maturity, fillet fat, fillet color, and gonad weight. The western stock fish grew faster and were significantly larger ( ) (P < 0.0001) than the eastern stock ( ). Heritabilities were low for all traits and ranged from 0.08 ± 0.06 to 0.28 ± 0.09. Genetic correlations for body size traits were highly positive and significant (0.99–1.00). Genetic correlations of fillet color and body size traits were positive, but not significant. Genetic correlations of fillet fat with body size traits were negative, but not significant. Genetic correlation of fillet fat and fillet color was positive and significant (0.55 ± 0.27). Random genetic variation was assessed from microsatellite variability on 30 fish from each stock (eastern and western) and 32 fish from a third commercial source of unknown origin for comparison. The amount of variation detected in the western stock was higher than the eastern and commercial stocks. The eastern stock was composed of an admixture of two sources, the commercial stock was composed by three different sources, and the western stock was composed by three to four source populations. Data will be used to calculate breeding values on a separate group of captive sibling adult broodfish and a line selected for carcass weight and maturity at 3 yr will be developed.