We present data on the effect of polarized laser radiation in the near IR region of the spectrum with wavelength 808 nm on the resistance of juvenile sturgeon to oxygen deficiency in the habitat when the fertilized roe are briefly exposed to radiation in the organogenesis stage. The magnitude of the stimulating effect depends on the exposure time (t) and power density (P) of the radiation and also on its modulation frequency (F). For optimal irradiation parameters (cw mode, P = 2.9 mW/cm 2 , t = 60 sec), the hardiness of the juveniles increases by a factor of ~1.5 compared with the control group. The maximum differences in the sensitivity of embryos to cw and pulsed radiation are observed for F = 1 Hz; as the modulation frequency increases up to F = 50 Hz, the magnitude of the photobiological effect approaches a level typical for cw exposure. We show that the duration of the dark period (pause time) between pulses is the critical parameter determining the dependence of the stimulating effect on the modulation frequency. We discuss questions concerning use of the indicated physical factor in the technology for raising sturgeon under industrial fish farming conditions. Introduction. Economically sound technologies for industrial raising of valuable fish species (sturgeon, salmon, whitefish) have attracted the attention of an increasing number of fish farms [1][2][3]. In this case, fish farming efficiency is mainly determined by the hardiness of the juvenile at the time it is released into artificial and natural bodies of water, in which it is subject to the effect of diverse biotic and abiotic habitat factors. The concentration of dissolved oxygen is an important factor in an aquatic environment, which fluctuates significantly both under artificial conditions and under farm conditions for raising a standard fish juvenile. When there is a deficiency of oxygen dissolved in the water, for the farm-raised juvenile we may observe a number of morphological deviations: head deformities, microcephaly (reduced brain size), underdeveloped gills, defects in the olfactory organs, etc. Most often, such a fish considerably lags behind normally developing individuals in size-weight parameters [1]. Furthermore, a significant deficiency of oxygen dissolved in the water can cause large-scale kills of fish fry. This is why development of methods for improving the resistance of juvenile fish to oxygen deficiency is an important problem in modern fish farming practice. There are quite good grounds for the interest of ichthyologists [4][5][6][7][8][9][10][11] in the stimulating effect of optical (including laser) radiation, which has been successfully used for a long time for treatment of human diseases [12,13], treatment and stimulation of weakened animals [14,15], and also for stimulation of plants [16,17]. However, attempts to use laser radiation in the red region of the spectrum (helium-neon laser, λ = 632.8 nm) in fish farming have shown that its effect on sturgeon and stellate sturgeon either proves to have (de-

In this work, for the first time, comparative studies of biological activity of low intensity continuous, quasi-continuous and pulsed laser radiation of nano-and picosecond time ranges with the same average power density are carried out. It is shown, that, despite the significant differences in peak values of intensity of acting factor, both continuous and quasi-continuous radiation and radiation of nano-and picosecond ranges are able to have both stimulating and inhibiting effects on all investigated parameters of functional activity of biological systems in a certain range of dose rates.The ability of laser radiation of near infra-red spectral region (800 -1340 nm) located out the absorption bands of main chromophores of cells to have regulatory effect on biochemical processes that control the hatching of branchiopod crustaceans Artemia salina L. upon irradiation of their cysts is revealed. The role of molecular oxygen and water as acceptors of laser radiation is discussed.

Sturgeons are valued as specialty black caviar, which is very expensive. Only females are used in the technology of caviar aquaculture. Universal method of sex determination has not yet been developed. Most of known methods are not sufficiently accurate, or used at a relatively late age, or difficult to use. Perfect early determination of sex is considered to be impossible. Because of the dark colour of most sturgeons and important morphological differences, which fish of almost all ages have, were overlooked. We first found that the scute structure of sterlet sturgeon depends on the sex. The found dependencies with the help of machine learning algorithms open a possibility for creation of sex determination equipment using the artificial intelligence. Our results open a perspective for creation of sex determination methods for other 23 sturgeon species, which can increase the efficiency of caviar aquaculture and restoration of sturgeons in natural waters.

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