No abstract

The purpose of the research was to study the peculiarities of the development of the Russian sturgeon in a specialized fish farm to assess the compliance of the technological conditions of cultivation with the biological needs and physiological characteristics of this type of sturgeon, as well as to ensure the further receipt of highquality fish products. The article considers histogenesis and morphological features of axial musculature of juvenile Russian sturgeon (Acipenser gueldenstaedtii) at the early stages of its formation, aspects of histological structure of musculature in the process of its differentiation into deep (musculus lateralis profundus) and superficial (musculus lateralis superficialis) lateral muscles. The formation and variability in diameter of muscle fibers of various types (oxidative and glycolytic) are discussed. It was found that the main part of the axial musculature is represented by a deep lateral muscle (musculus lateralis profundus). This muscle is formed by typical white (glycolytic) fibers. A smaller part of the axial musculature is represented by red (oxidative) type fibers. The results of the studies indicate the heterogeneity of the studied structures and the uneven period of fiber growth in different parts of the body, a large variability in the diameter of glycolytic fibers in the fingerlings of the Russian sturgeon. Together with the data on the beginning of differentiation of deep and lateral fibers at the age of one month, this allows us to estimate the approximate time of laying the main muscles and pay special attention to nutrition and conditions of fish keeping. The absence of pathologies in the structure and development of muscle fibers suggests that the cultivation of sturgeon fish in a cooling pond on running water is more favorable for the health of fish, unlike farms with closed water supply.

Acclimatized in the last century in the reservoirs of Russia, the white silver carp is the only consumer of phytoplankton in our country. In conditions of artificial reproduction and domestication, uncontrolled deterioration of fish habitus often occurs. In this regard, a comparative analysis of the variability of the most informative morphological parameters, namely length, mass, head length, body girth and their main indices in the samples of the white silver carp of varying degrees of domestication, was carried out. The Chinese, Amur and local lineages, the Ergenin sample and the Romanian population were studied, of which the least domesticated is the Chinese line. The presented materials show that the Chinese white carp line of the second generation of domestication differs in a smaller head, high indices of relative head length and physical development from the local and Ergeninsky fish samples domesticated for several decades. In pond lines domesticated in several generations, there is an increase in the relative size of the head and a deterioration in the index of physical development, which indicates the presence of selection for fitness to insufficient food supply in conditions of weak flow. It is recommended in the breeding program when growing reproductive herds of white carp in ponds to provide for selection to preserve the commercial qualities of fish.

The mottled silver carp is one of the best reclamation plants for eutrophic reservoirs. Since the middle of the last century, it has been widely acclimatized almost all over the world. Due to the fact that habitat conditions have a certain influence on the habitus of fish, a comparative analysis of the variability of the most informative morphological parameters, namely, length, mass, head length, body girth and their derived indices of the totality of individuals of variegated silver carp of varying degrees of domestication from the reservoirs of Romania and Russia with the first generation of domestication of fish from the Chinese population of unknown origin, was carried out. As a result of the research, it was revealed that the fish of the first generation of the Chinese natural population have a smaller head, and the weight, relative to the length of the body, is greater than that of the fish of the Ergenin, local and Romanian populations adapted to ponds in several generations. Comparison of local and Ergeninsky samples of fish indicates a tendency to deterioration of the index of physical development in the process of domestication and weakening of correlations between traits. The change in the indices of domesticated pond lines towards an increase in the relative size of the head and a deterioration in the index of physical development indicates the presence of selection for adaptation to conditions of low flow and restrictions in oxygen supply, and also causes a decrease in the commercial attractiveness of the pond mottled silver carp in the process of domestication. It is recommended when growing reproductive herds of variegated silver carp in ponds in the breeding program, in addition to breeding to consolidate technologically useful features, it is necessary to provide for selection to preserve the commercial qualities of fish.