Ecological and Biochemical Status of the Atlantic Salmon Salmo salar L. and the Brown Trout Salmo trutta L. at Early Stages of Development

A review of original and published data on the biochemical status of two salmonid species, the Atlantic salmon Salmo salar L. and the brown trout Salmo trutta L., encompasses the results on fish embryogenesis and the early development of fry of different ages during the freshwater period of life at different stages of life history (fingerling, parr, smolt) with inhabitation of the riverine biotopes of the northwest Russia, which differ in ecological and hydrological conditions. Data on the total lipid content, reserve lipids (triglycerides and cholesterol ester) and structural lipids (phospholipids and their fractions, cholesterol), fatty acids, activity of enzymes of carbohydrate metabolism, energy metabolism, and intracellular proteolysis are considered, along with some molecular-genetic indices of muscular tissue growth (the expression level of genes controlling myogenesis, as well as myostatin and heavy chain of myosin). Biochemical differences are already found in the embryos of the studied salmon fish; they determine the specifics of the interaction of larvae and fry with the habitat. As a result, when leaving the redds, some hatchlings may have certain metabolic advantages that facilitate their settling on better nursery grounds. Among all of the studied age groups, the “youngest” groups (0+, 1+) stand out, both in regard to the level of biochemical metabolism and the degree of difference between phenotypic groups inhabiting microbiotopes with different ecological, trophic, and hydrological conditions.