1a. Objectives (from AD-416)
1: Define phenotypic measures and estimate genetic and phenotypic parameters for commercially important traits such as growth, cold tolerance, fillet color, and fat content in Atlantic salmon. • 1A. Define phenotypic measures and estimate genetic parameters for growth (carcass weight), fillet color, and fillet fat content in Atlantic salmon. • 1B. Define phenotypic measures and estimate genetic parameters for cold tolerance in Atlantic salmon. 2: Develop a multi-trait selection index to produce and release Atlantic salmon germplasm selected for multiple traits.
1b. Approach (from AD-416)
The research program supports the coldwater aquaculture industry with a breeding program developing improved lines of North American Atlantic salmon. Atlantic salmon cultured in research objectives in the breeding program is based on life stage and separation of year classes. An incubation system will be used for eggs and newly hatched fry before first feeding, parr tanks are used for first feeding fry to 30-40 g salmon, smolt tanks are for 30-40 g to 100 g pit tagged salmon, on-grow tanks are for 100 g to 1.0 kg salmon in their second year, 3-yr old broodstock tanks are for 1.0 kg to 3.0 kg salmon, and one 4-yr old broodstock tank is for growing salmon to 3.0 kg to 6.0 kg until spawning. Up to 224 families of Atlantic salmon with 300-500 eggs/family will be cultured each year. Approximately 250 eggs will be saved from each family mating and raised through parr size. Typically 30-40 smolts per family will be saved as nucleus of fish for the breeding program and cultured in biosecure tanks will become broodfish. Additional 30-40 smolts per family will be cultured and transferred to an industry collaborator for stocking into net pens for performance evaluations. Net pen fish will be cultured to market size, harvested from sea cages, and transported to a commercial processing plant. Data will be collected for carcass weight, sex, and stage of sexual maturity. Muscle tissue samples will be collected from each fish for fat and pigment analyses. A separate group of fish from each family will be pit tagged as smolts, cultured to 2-year old sub-marketable size and stocked into replicated fish culture tanks equipped filled with filtered, UV-treated seawater in a recirculation biofilter system. The water temperature will be lowered approximately 1C per day using a glycol-based chiller system capable of chilling seawater temperatures down to approximately -2C. Individual fish will be scored on the basis of temperature and time to loss of equilibrium and death and survival. Data will be analyzed to calculate phenotypic and genetic variation for carcass weight, fillet color, fillet fat, and cold tolerance traits. Heritabilities, breeding values, and genetic correlations for carcass weight, fillet fat, fillet color, and temperature tolerance obtained from performance data will be used to develop a selection index or index of merit for each individual broodfish chosen for spawning in a selected line. Selection of 4 year old fish for spawning will occur when fish are moved from 3-yr old broodstock tanks into the 4-yr brood stock system prior to the spawning season. Relative economic weights for each trait will be determined in consultation with industry collaborators and account for the market value of each trait. Germplasm from an Atlantic salmon line selected for multiple traits will be released to commercial producers and consumers.
3. Progress Report
Pedigreed families were produced by spawning broodstock selected for improved carcass weight from the 2006 year class of salmon already in the NCWMAC breeding program. Fish from the 2006 year class had been cultured in marine net pens in collaboration with industry, and growth data were analyzed to obtain estimated breeding values on broodfish to be spawned as a line selected for increased carcass weight. The mean carcass weight for 2006 year class St. John’s stock fish from the NCWMAC breeding program was 5.04 kg compared to a mean carcass weight of 3.93 kg for industry fish cultured under the same conditions. NCWMAC fish were 28% larger than industry fish and 114% larger than wild Penobscot River fish (2.35 kg) used as a control line. Data was used to calculate breeding values on captive sibling adult broodfish and a line of St. John’s River fish was selected for carcass weight and spawned in the fall of 2010. Breeding values of female (N=192) brood fish ranged from --225 to +913 g (mean=341) and male (N=97) breeding values ranged from -514 to +913 g (mean=385). A total of 192 viable families were produced with mean breeding value of +363 g (+0.16 SD from the population mean) for this select population. Eyed eggs were disinfected and incubated in separate hatching jars or trays. Fry were transferred to separate rearing tanks prior to first feeding and are being raised to parr size. When the fish reach 20-40 grams, individual fish will be pit tagged and cultured communally before being stocked into sea cages for performance evaluations and some fish will also be exposed to superchill temperatures for evaluation of cold tolerance. Research objectives of the NCWMAC fall within one main area defined by the USDA/ARS Aquaculture National Program 106 Component 1: Understanding, Improving, and Effectively Using Animal Genetic and Genomic Resources and NP Action Plan Problem Statement 1B: Develop and Implement Genetic Improvement Programs. The current research objective is part of the ARS breeding program to improve cold tolerance of Atlantic salmon. Fish of the appropriate size are available for cold water challenges to improve this trait.