Reducing environmental sensitivity

Atlantic salmon (1.2 million tons) and rainbow trout (70 thousand tons) are the main aquaculture production in Norway. High growth rate of the fish is an important trait for the economics of the fish farmer. In order for the fish to maintain high growth, the rearing conditions needs to be optimal. In the grow-out phase, the fish are reared under natural conditions in net cages in the sea where in environmental conditions both within and between years. For the fish farmer it is advantageous if the fish has a high growth rate even when environmental conditions are changing. A fish whose growth performance is changed in response to variations in macro-environments, such as different water temperature, salinity, and photoperiod in different locations, can be defined as having low stability of growth and being sensitive to the macro-environment. In contrast, fish can also be sensitive to a micro-environment, which for example fluctuating environmental factor within a fish tank leads to size variation within a group of fish of the same age. The project STABLEFISH, conducted by Nofima AS in collaboration with Animal Breeding and Genomics Centre (ABGC) in Wageningen University and Biometrical Genetics in MTT Agrifood Research Finland, focuses on the possibility to increase stability of growth by reducing the environmental sensitivity of fish through selective breeding. The genetic variation of macro and micro environmental sensitivities of growth in rainbow trout has been quantified. The results reveal that macro and micro environmental sensitivities of growth are genetically determined, indicating the possibility to reduce environmental sensitivities by selective breeding. This means that we will be able to breed fish, which will be more uniform in growth and will be well adapted to multiple environments and variable environmental conditions. However, accuracy of selection and consequently selection response may be low because sensitivity is a trait measured from a group of animals. The use of genomic information increases the accuracy of selection for micro-environmental sensitivity, suggesting that higher response to selection for micro-environmental sensitivity can be achieved when genomic information are available.

Atlantic salmon (1.2 million tons) and rainbow trout (70 thousand tons) are the main aquaculture production in Norway. Growth is one of the most important traits. Fish may not be able to maintain high growth when the rearing conditions are not optimal. I n the grow-out phase, the fish are reared under natural conditions in net cages in the sea with variation in environmental conditions both within and between years. A fish whose growth performance is changed in response to variations in macro-environments , e.g., different locations, can be defined as having low stability of growth and being macro-environmental sensitive. In contrast, micro-environmental sensitivity refers to the variation within a macro-environment, leading to size variation within a grou p of fish of the same age.The project STABLEFISH focuses on the possibility to increase stability of growth by reducing the environmental sensitivities through selective breeding. First, genetic variation in macro and micro environmental sensitivity will be estimated. Second, the possibility to select against macro environmental sensitivity will be investigated using genomic information. Finally, Smoltified fish are transferred to the sea which is one of the major environmental changes in their life, lead ing to considerable genetic change in micro-environmental sensitivity. Genetic change in micro-environmental sensitivity in different life stages will be studied. Stability of growth performance in farmed fish, being well adapted to multiple environments and variable environmental conditions increases animal welfare and reduces fish mortality and losses. Being able to create more uniformly performing fish stocks will allow harvesting a larger proportion at an appropriate body size. There will be less comp etitive interaction among the animals, contributing to more efficient feeding and better fish welfare. This will improve consumer acceptance of farmed fish and contribute to increases in aquaculture industry profit.