Effects of cultivation of the fish breeders and juveniles in salt solutions of different concentrations
Authors:   FGBU “SPBGAU”, Garlov P. E. , Arshanitsa N. M. ,   St. Petersburg branch of VNIRO (GosNiORCh) in honour L. S. Berg), Shinkarevich E. D. ,   St. Petersburg branch of VNIRO (GosNiORCh) in honour L. S. Berg), Stekolnikov A. A. ,   St. Petersburg branch of VNIRO (GosNiORCh) in honour L. S. Berg), Grebtsov M. R. ,   St. Petersburg branch of VNIRO (GosNiORCh) in honour L. S. Berg), Bugrimov B. S. ,   St. Petersburg branch of VNIRO (GosNiORCh) in honour L. S. Berg)
Published: November 2020

The aim of the research is to develop new efficient method of fish cultivation in a medium with totally controlled conditions. The main task is the morpho-physiological and piscicultural-biological analysis effects of farming fish- breeders and juvenils in salt solutions of different concentrations. Laboratory and industrial fish contents tests for sea water and salt solutions medium of different salinity have been implemented on the most valuable fish species: russian and stellate sturgeon, rainbow trout, bullhead and roach.The results were evaluated by piscicultural-biological and physiological indicators: content state of hemoglobin, total protein, serum osmolarity, abdominal fluid and urine. Cytomorphometrical analysis of the hypothalamic-hypophysial neurosecreto-ry system (HHNS) status was performed by light and electron microscopy. The enhance effects of fish survival, breeders reproductive quality, youngs growth rates were first established for medi-um with "critical" salinity 4-8‰ For breed-ers originally it was shown the possibility to change sea water on the table salt solution of the same concentration. With such a low concentration of salt a new biostimulating effect of this artificial medium on the fish body was installed, due to the absence of its well-known toxicity. The highest degree of survival and delayed sex maturation of roach and stellate sturgeon were specifically in-stalled for the same concentration of indus-trial salt solutions. The best physiological body state was also shown in this solution (5‰) by physiological and biochemical analysis, regarding minimal losses in hemo-globin and serum protein. Histophysiological analysis of the sevruga HHNS state showed the smallest degree of activity in this solu-tion to the end of the experience, proportion-ate to the severity of stress. Such moderately active HHNS in solution of salt 5‰ clearly indicates the status of the eustress and high HHNS activity for control groups indicates the typical status of the stress. By electron microscopy study HHNS state sevruga and sturgeon in hypertonic salt solutions of dif-ferent concentrations it was shown, that at 17 and 22‰ they were under stress and at 32‰ represented irreversible disstress. All 3 in-stalled stress status depends on the intensity and duration of exposure. Their effects are alternative and therefore are managed, trans-forming from bio-stimulation in reversable stress and, after reaching the limits of physi-ological species cause toxic effect and then a state of disstress and death. The possibility of changing the sea water to industrial salt solution 5-7‰, allowed to develop "A meth-od to reserve fish breeders", which ,however, can not be applied for the young fish breed-ing. So the next stage in the development of this method was to test it already on juvenile and young fish, in order to determine its effective cultivation in this artificial biostim-ulating medium. The results of the search experience on trout fingerlings showed the increased survival and growth in salt solu-tions, especially in 12‰ as compared to con-trol. The first experimental verification of this method on the clarias bullhead finger-lings in the recycling aquacultural system (RAS) showed the largest growth rates in 5‰ salt solution, and its total survival in all variants. Received data and analysis of biostimu-lated effects impact on the body's critical salinity gives the opportunity to develop a fundamentally new way of cultivation of valuable fish species in an artificial biostim-ulated habitat. This technique can allow to manage breeding - obtaining offspring and the cultivation of young fish. It is aimed at improving the efficiency of breeding fish in aquaculture due to the availability of the application for any type of fish farms with the effects of increasing survival rate and young growth rate. It is expected that the change of the sea water with the cheap solu-tion of table salt can be widely practiced at fish plants in various fields and at all stages of fish biotechnology works, especially RAS.