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 biochemical status of salmonids (the Atlantic salmon Salmo salar L. and the brown trout Salmo trutta L.) encompasses the results obtained when studying fishes' embryogenesis, early development of fry of different age during the freshwater period of life at different stages of life history (fingerlings, parr, smolts) inhabiting biotopes (rivers) of North-West Russia that differ in ecological and hydrological conditions. The data are considered on total lipid content, reserve (triglycerides and cholesterol ester) and structural (phospholipids and their fractions, cholesterol) lipids, fatty acids, activity of enzymes of carbohydrate metabolism, energy metabolism, and intracellular proteolysis, along with some molecular-genetic indices of muscular tissue growth (the expression level of genes controlling myogenesis, also myostatin and heavy chain of myosin). Biochemical distinctions are already evident in embryos of salmonids under study, which determine the specific relations of larvae and alevins with the environment. As a result, when dispersing from redds, a part of hatchlings may have certain metabolic advantages which facilitate their occupying the better nursery grounds. It is shown that, among all the age groups studied, the 'youngest' groups (0+, 1+) stand out, both in the level of biochemical metabolism and the extent of distinctions between phenotypic groups inhabiting micro-biotopes with different ecological, trophic, and hydrological conditions.