Temporal variability of catches, distribution and dynamics of length of Russian sturgeon in waters of the Caspian Sea in 2015 –2020

The paper presents long-term data on catches, distribution and length dynamics of Russian sturgeon in the waters of the Caspian Sea for the summer-autumn periods in 2015-2020. When considering the catches in the different parts of the sea there is found their annual variability, which is especially noticeable in the shallow zone in the North Caspian (0.31-2.0 specimens/trawl) and in the Middle Caspian (0-1.31 specimens/trawl). In the course of determining the reasons for the interannual dynamics of catches there were revealed several decadal rises. The dependence of decadal catches on the temperature of the bottom water layer was analyzed. The highest rise in catches was observed in the first decade of September when the temperature of water lowered up to 20.0-15.0 °C. The increase was observed due to migrating individuals to the shallow zone of the Northern Caspian Sea from shallow waters. Despite the variability of catches, the localization of Russian sturgeon schooling in the northern and middle part of the sea during the summer-autumn periods of 2015-2020 has certain similar features and trends. Sturgeon species fed mainly on shallow banks and deep dumps, where the largest catches of sturgeon were recorded from 5.0 to 12.0 specimens/trawl. The absence of sturgeon at depths of up to 3.0 m isobath in the last five years is due to the water heating up to 27.6-28.8 °C. The decrease in the length of the Russian sturgeon observed in recent years is due to an increase in the proportion of youngsters (19.2-70.0%) against the background of a decrease in the adult population. It should be noted that from 2017 to 2019 there were not found the adult species in the catches by fishing nets, which indicates their continued re-moval from the population.

Study of the properties of the ovarian fluid of the Russian sturgeon (Acipenser gueldenstaedtii Brandt, 1833) during freezing

The process of freezing the ovarian fluid of the Russian sturgeon (Acipenser gueldenstaedtii Brandt, 1833) was analyzed. With gradual cooling from 22°C to -196°C at a rate of 10° per minute, the process of freezing, formation and change of ice microparticles was observed. The ovarian liquid was glazed at -5°C and only at -70°. With the microparticles of ice began to form. From that moment, up to the temperature of liquid nitrogen (-196°C), the microparticles were crushed into smaller ones. The high content of intracellular water in the ovarian fluid of female Russian sturgeon contributes to the formation of the bulk of microparticles of ice, which is confirmed by their shape. These particles, which have sharp edges, are able to damage the thin shells of eggs during deep freezing.

Some aspects of fishery development of sturgeon hybrids in Russia. Part 2

With the development of commercial sturgeon breeding, creating hybrid forms of sturgeon fish in order to obtain a larger volume of gourmet marketable products is of increasing interest to fish farmers. The choice of objects for creating hybrid forms for commercial cultivation depends on the conditions and biotechnologies of intensive fish culture. One of the widely used technologies that can several times reduce the time for growing objects and receive viable juveniles and marketable products year-round is the technology using recirculating aquaculture system (RAS). With this cultivation technique, the advantage is given to species with high adaptive capabilities and growth intensity. The most popular objects for hybridization and creation of hybrid forms are beluga, sterlet, Siberian and Russian sturgeon, etc. Beluga is the largest representative of the sturgeon family. It reaches commodity weight (3–5 kg) against the background of natural temperatures within 2–3 years. The Sterlet is a pure freshwater form. It is an excellent object for cross-breeding with other sturgeon species, in particular with beluga to obtain a bester hybrid. The Siberian sturgeon grows most intensively at a temperature of 15–25°C, however, the growth persists at lower temperatures (1–10°C). The Russian sturgeon in artificial conditions reaches a marketable weight of 1.5–3.0 kg in the second-third years of cultivation. In order to facilitate the orientation of fish farms, fish farmers engaged in the production of commercial products, the article discusses the creation of hybrid forms of sturgeon fish in domestic and foreign aquaculture, provides their brief fish-breeding and biological characteristics when grown in fish farms of various types. Knowledge of the fish-breeding and biological characteristics of sturgeon fish species hybrids when grown in specific conditions will make it possible to successfully introduce them into the practice of commercial cultivation. English version of the article is available at URL: https://panor.ru/articles/some-aspects-of-fishery-development-of-sturgeon-hybrids-in-russia-part-2/74467.html

Some aspects of fishery development of sturgeon hybrids in Russia. Part 1

With the development of commercial sturgeon breeding, creating hybrid forms of sturgeon fish in order to obtain a larger volume of gourmet marketable products is of increasing interest to fish farmers. The choice of objects for creating hybrid forms for commercial cultivation depends on the conditions and biotechnologies of intensive fish culture. One of the widely used technologies that can several times reduce the time for growing objects and receive viable juveniles and marketable products year-round is the technology using recirculating aquaculture system (RAS). With this cultivation technique, the advantage is given to species with high adaptive capabilities and growth intensity. The most popular objects for hybridization and creation of hybrid forms are beluga, sterlet, Siberian and Russian sturgeon, etc. Beluga is the largest representative of the sturgeon family. It reaches commodity weight (3–5 kg) against the background of natural temperatures within 2–3 years. The Sterlet is a pure freshwater form. It is an excellent object for cross-breeding with other sturgeon species, in particular with beluga to obtain a bester hybrid. The Siberian sturgeon grows most intensively at a temperature of 15–25 °C, however, the growth persists at lower temperatures (1–10 °C). The Russian sturgeon in artificial conditions reaches a marketable weight of 1.5–3.0 kg in the second-third years of cultivation. In order to facilitate the orientation of fish farms, fish farmers engaged in the production of commercial products, the article discusses the creation of hybrid forms of sturgeon fish in domestic and foreign aquaculture, provides their brief fish-breeding and biological characteristics when grown in fish farms of various types. Knowledge of the fish-breeding and biological characteristics of sturgeon fish species hybrids when grown in specific conditions will make it possible to successfully introduce them into the practice of commercial cultivation.