Title: Sources of Phenotypic and Genetic Variation for Seawater Growth in Five North American Atlantic Salmon Stocks Author
Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 16, 2008
Publication Date: April 1, 2010
Citation: Wolters, W.R. 2010. Sources of Phenotypic and Genetic Variation for Seawater Growth in Five North American Atlantic Salmon Stocks. Journal of the World Aquaculture Society. 41:421-429. Interpretive Summary: Atlantic salmon aquaculture is one of the most successful global aquaculture enterprises, and has wide acceptance as a main food item by American consumers. Regulations on environmental issues, mandatory stocking of 100 percent native North American salmon (in an effort to protect populations of federally endangered wild Atlantic salmon), and disease have impacted economic viability of the U.S. salmon industry. In response to these problems, the Agricultural Research Service (ARS) developed the National Cold Water Marine Aquaculture Center (NCWMAC) Atlantic salmon breeding program Franklin, Maine. Development of salmon germplasm with increased growth, feed efficiency, reproductive success, processing characteristics, and disease resistance will improve production efficiency and sustainability of the U.S. salmon industry. The breeding program initiated by the NCWMAC has the goal to improve commercially important traits in salmon and develop improved germplasm for release to U.S. producers and consumers. Atlantic salmon were obtained from two St. John’s River sources, Penobscot River, Gaspe´, and landlocked salmon stocks and performance evaluated in commercial net pens in collaboration with industry partners. Results from this study indicate the St. John’s River stocks to have the most potential for commercial culture. Most salmon currently cultured in the Northeastern US and Atlantic Canada are from the St. John’s stock, and this stock is also being cultured in other areas of the world with excellent results. Results show that selective breeding at least for carcass weight or growth is likely to be successful. However, a sustained breeding program is critically needed to continue addressing specific concerns and culture requirements for the North American geographic area and commercial industry. Although additional traits of economic importance should and will be considered, growth rate, survival, and sexual maturity were considered to be of primary importance in this initial study, and have major impact on economic return.
Technical Abstract: In 2003 pedigreed families were obtained from two St. John’s River sources, Penobscot River, Gaspe´, and landlocked salmon stocks. Eyed eggs were disinfected upon arrival, and incubated in separate hatching jars. Fry were transferred prior to first feeding into individual 0.1-m3 tanks receiving 8 l/min of oxygen-saturated freshwater from a recirculating biological filtration system. At approximately 30 days after initiation of feeding, fish densities were equalized to 250 fish/tank, fed 5% of the tank’s total biomass in 3-4 daily feedings. When the fish were ~40 grams, approximately 30 fish from each family were pit tagged and stocked communally into three replicated 10-m3 smolt tanks. Approximately one month prior to stocking into sea cages for performance evaluations, evaluations of serum chloride levels and gill Na+, K+ - ATPase activity were measured on sub-samples from all stocks in freshwater and following seawater challenge. Smolts were stocked into sea cages in June 2005, harvested in February 2007, and evaluated for carcass weight, sex, and stage of sexual maturity. Data were analyzed by mixed model analysis of variance to determine the random effects of sire and dam (sire), and the fixed effects of sex, salmon stock, ploidy level, and replicate smolt tank on carcass weight with smolt weight as a covariate. Sire and dam variance components were significantly different from zero, and the fixed effects of salmon stock, sex*stock interaction, and smolt weight at stocking were significant (p<0.05). There were no significant differences between sexes, replicate smolt tank, or ploidy level for carcass weight. Overall St. John’s River fish had the fastest growth with a carcass weight >4.1 kg compared to the slowest growth in landlocked fish at 1.7 kg. Grilsing was also highest in St. John’s River fish (~6%) and lowest in Penobscot River fish (0%). The sire heritability for carcass weight calculated from the sire variance component using mixed model analysis of variance (SAS) or MTDFREML was 0.26+0.14. Data was used to calculate breeding values on captive sibling adult brood fish and a line selected for carcass weight were spawned in the fall of 2007, and eggs from these fish were released to industry.