Experimental hybridization and competition between Atlantic salmon (Salmo salar) and native salmonid species in Japan

Atlantic salmon (Salmo salar) is a leading aquaculture species that has been extensively bred in Norway using selective DNA marker technologies. The commercial application of a high-growth transgenic Atlantic salmon (namely AquAdvantage® Salmon) was approved by the United State Food and Drug Administration in November 2015. AquAdvantage salmon is a strain of Atlantic salmon that has been genetically modified by the integration of a growth-hormone regulating gene from a Chinook salmon and the antifreeze protein gene promoter from the ocean pout. The GM strain grows at least twice as fast as regular farmed Atlantic salmon. Should it become a candidate for commercial production in Japan, there is not enough available information on the biology and ecology of Atlantic salmon in Japanese waters for comparison. To remedy this in part, we evaluated the maturation of experimentally reared Atlantic salmon in Japan, and tested the potential of the species for hybridization and competition with four native salmonid species. Seasonal water temperature was a primary determinant of maturation of the Atlantic salmon. Crossed with Amago salmon, Masu salmon, and Biwa trout, most of the hybrid embryos ceased to develop between mesoderm induction and axis formation. However, a relatively low number of the Atlantic salmon and native white potted char (Salvelinus leucomaenis) hybrid, as confirmed through restriction fragment length polymerase analysis, survived for 2 years. In addition, we reared different life stages of Atlantic salmon and three native salmonid species in tanks or ponds to determine the extent of interspecific and intraspecific competition for food and space, as well as related changes in body mass. We found that competition was dependent on the combination of salmonid species and life stage of the different species.