Regularities of the life history strategy adoption in masu salmon Oncorhynchus masou from the Kol River (Western Kamchatka) in regard to the processes of growth and sexual maturation

Growth, age structure, sexual maturation, and peculiarities of the life history strategy adoption were studied for the population of masu salmon Oncorhynchus masou inhabiting the Kol River, Western Kamchatka. The growth rate and gametogenesis depended on the peculiarities of masu salmon generations in certain years and were the limiting factors for the juvenile differentiation and the direction of its ontogenetic development. The adoption of the resident or anadromous life history strategy in masu salmon is the epigenetic process, and the bifurcation during the life span of a single specimen is observed only once in a life, but twice in the generation, at the age of 1+ or 2+. The diversity of the life history strategy patterns was less at the northern boundary of the geographical range of masu salmon compared to the area of ecological optimum (the basin of the Sea of Japan). In the Kol River basin, nearby the northern boundary of its geographical range, the reproductive success and formation of the life history strategy diversity in the population depended strictly on the temperature regime of the water bodies, where the spawning and the freshwater period of life cycle of masu salmon take place. In Kamchatka, all the breeders were monocyclic, i.e. anadromous and resident precocious males spawned only once in a life.