For successful development of aquaculture, fish farms have to be provided by effective means and methods to prevent and treat diseases of fish. Many drugs are limited for using in aquaculture, so the influence of each particular drug or chemical substance on the fish development should be investigated carefully. Effectiveness of chemical solutions for suppressing the growth of saprolegnium micromycetes on egg membranes and other tissues of sturgeon embryos during their incubation is evaluated. The experiment was conducted at the research and experimental base BIOS belonged to the Russian Res. Inst. of Fisheries and Oceanography, Volga-Caspian branch (CaspNIRKh) located in Astrakhan and included a series of observations on incubation of sturgeon eggs processed with solutions of some chemicals (Purple-K, sodium chloride, hydrogen peroxide) or drug (Iodinol). Two sturgeon species (russian sturgeon and beluga) were tested with measuring biological parameters of their embryos, as survival rate, contamination by saprolegnia micromycetes, number of abnormally developing embryos, and number of obtained prelarvae. The processing with 0.05 % solution of hydrogen peroxide (10 min. exposure) and with 0.90 % solution of sodium chloride (3 min. exposure) showed the best results: these solutions made the lowest negative effect on the embryos survival but reduced significantly infection of incubated eggs.
The fishing and biological characteristics of the common sprat (Clupeonella cultriventris caspia Svetovidov, 1941), caught along the coast of the Caspian Sea in the area of Makhachkala, the Republic of Dagestan, were obtained. Examination of the fish showed that the individuals were in a spawning state. In the muscles, the content of the main reserve and energy substances of the body — total lipids and water-soluble protein — was studied. A significant (p < 0.05) positive correlation was registered in females and males between fish weight and fishing length: (r = +0.87) and (r = +0.85), respectively. The physiological state of the common sprat in terms of the content of total lipids and water-soluble protein in the muscle tissue is satisfactory. The tendency of the highest content of total lipids in the muscles of females compared to males was registered, since individuals need a larger energy reserve to ensure oogenesis than for spermatogenesis. This is due to the use of muscle lipids to build the gonads and supply with the necessary nutrients for the embryo, and later the larva. In a comparative aspect, there were no significant differences in the content of water-soluble protein in the muscles of males and females during the spawning period. Analysis of the coastal fishery for common sprat with fixed seines in the period 2011–2021 showed that its catch on the Dagestan coast of the Caspian Sea increased from 302.7 tons in 2012 to 1815.0 tons in 2021, which was in direct proportion to the number of fixed seines. In this regard, the most actual task is the development of fishing reserves of this species, which will contribute to the development of the fish extraction and fish processing industry of the Republic of Dagestan.
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