Marking fin spine of juvenile sturgeon (acipenseriformes: acipenseridae) using oxytetracycline and the comparing of growth performance

ABSTRACT This study aimed to describe and validate the formation of the rings in the spine of the pectoral fin and to determine the coherence of the OTC mark with the rings of three species of Caspian Sea sturgeon, the Persian sturgeon (Acipenser persicus), the Starry sturgeon (Acipenser stellatus) and Ship sturgeon (Acipenser nudiventris). Validation was achieved by comparing the total radius of the fin spine of fish of known age after one and two years of growth with the measured radius of the first and second rings in the zone. There was no overlap between the measured radius for the first year and the increase for the second. The Ship sturgeon showed the largest width of the second ring followed by the Persian sturgeon and Stellate sturgeon. The results indicate that the highest growth parameter belongs to the juvenile Ship sturgeon. This research showed that chemically marking the fin spines of juvenile Acipenseridae leads to unbiased estimates and contributes to the knowledge of the population dynamics of these species. The study found that the combination of the dial ring of the pectoral fin spine with growth validated the age estimation in juvenile sturgeon Ship, Persian, and Starry sturgeon.

Dependence of the duration of the embryonic period of development of the sevryuga (Acipenser stellatus Pallas, 1771) and the thorn (Acipenser nudiventris Lovetsky, 1828) on the temperature regime of wintering of producers

The temperature conditions and the results of wintering of producers, incubation of caviar of sevryuga and thorn in farms on waste warm waters are considered. The studied indicators are compared with similar data obtained when keeping producers from natural populations in the lower reaches of the Volga River. In the considered species, with a shortened and comfortable "warm" wintering (for sevryuga at 5-11, thorn – 3-15°C), an increase in the duration of incubation up to a day or more was recorded in comparison with individuals from natural populations. The temperature regulations of wintering for producers, incubation and maintenance of free embryos are proposed.

PHYSIOLOGICAL INDICES OF BELUGA AND SHIP AND THEIR INTERSPECIFIC HYBRIDS IN FISH-FARM CONDITIONS

The objects of research are Beluga (Huso huso, Linnaeus), sturgeon spike (Acipenser nudiventris, Lovetsky) and their interspecific hybrids of artificial generation grown on the Research and Experimental Base BIOS (the Astrakhan region) by using the basin method. To assess the physiological status of fish, a set of morphophysiological indicators (absolute and relative weight of gills, heart, liver, and gonads) were used. The dynamics of the indices of the corresponding viscera of Beluga and sturgeon spike and their interspecific hybrids in the second year of cultivation was studied. The necessity for the research is explained by the fact that most work performed was carried out on land vertebrates and on fish of natural generation. There have been presented the average values of morphophysiological indices for each of the four groups of unmixed sturgeon species and their hybrids. The obtained values of the studied parameters of sturgeon species can be used for further monitoring of the fish growing conditions using the basin method.

ANALYSIS OF BIOLOGY AND REPRODUCTION OF SHIP STURGEON (ACIPENSER NUDIVENTRIS)

The article presents the analysis of the research literature on biology, ecology, artificial and natural reproduction, behavior, nutrition and taxonomic status of ship sturgeon (Acipenser nudiventris Lovetsky, 1828) over the period 1877-2020. There are given the private data obtained during interviews with fishermen, which was published earlier. The approaches to ship artificial reproduction have been analyzed; the corresponding data from the Russian research literature and from the foreign sources are presented.Ship sturgeon is one of the most vulnerable and small in number sturgeon species in the world, the individuals of which are still found in the Balkhash-Ili basin (Kazakhstan-China) due to its invasion in 1933-1934. It should be mentioned that this is the only example of successful acclimatization of sturgeon. Ship sturgeons have the following ecological and biological characteristics: prolonged living in the mountain rivers with downstream migration into the delta and the sea coast; high rates of fertility coupled with high mortality rates in early ontogeny; a diverse diet depending on the habitat. Artificial reproduction of ship sturgeon was started in 1941 in Azerbaijani SSR. Unfortunately, the species did not receive a proper attention because of its scarcity in the natural habitat, which resulted in their complete disappearance. Today the conservation of ship species requires taking the urgent measures: forming ship broodstock, introducing it into aquaculture, clarification of reproductive biotechnology, studying the peculiarities of ship growth and maturation in the fish farms.

To the question of variability of number of micropyles in oocytes of ship sturgeon (Acipenser nudiventris)

The paper considers the characteristics of the gametes, habitats and spawning conditions of sturgeon, which are important for improving the biotechnology of their artificial reproduction. Based on the native data and literature, there have been analyzed the limits of variation of micropyle of ship sturgeon (Acipenser nudiventris Lovetsky, 1828) and some other species, as well as the features of the micropylar complex. The material for the study conducted in 2018-2019 served the ovulated eggs and caviar from the broodstock of the second-third generation of ship sturgeon, which contained in the conditions of the State Regional Centre for Sturgeon Gene Pool Conservation “Kubanbioresursi”. Ship sturgeon has been found to have the largest average number of micropyles among low-chromosomal species. In the main sample, the number of micropyles varied from 2 to 41, with an average value of 11.09 ± 0.24 and a concentration of indicators from 2 to 19 (94%). The location peculiarity and a slight variation in the number of micropyles in one female species of ship sturgeon have been revealed, as well as the different shape of a micropylar complex, as opposed to the similar shapes in other sturgeon species: ship sturgeon has not the funnel-shaped micropylar complex, but the bowl-shaped one. The ship sturgeon spawns under conditions of high water speed and a micropylar bowl, the diameter of which exceeds 2-3 times the diameter of the funnel and increases the collection area of the highly diluted seminal fluid. From a practical point of view, studying these features is important for improving the biotechnology of artificial insemination of roe of rare species in conditions of almost complete absence of natural reproduction in natural conditions.

The Structure of the Natural Microbiome of Sturgeons

In order to determine the structure of the natural microbiome of sturgeons grown in a recirculating aquaculture system, samples from the surfaces of the fish body and systems of organs that have the most frequent contacts with external environment (surface of the skin, respiratory and digestive organs of fish) were studied. Pieces of fins, fragments of gill filaments and contents of the intestine were taken from ten conditionally healthy spiny sturgeons (Acipenser nudiventris) kept in two nursery pools and were used as the material for research. To conduct the study of the metagenome of sturgeon fish, the following was performed: extraction of DNA samples in accordance with the kit manufacturer instructions; analysis of the nucleotide sequence of the fragments; processing of the obtained sequences using conventional methods. The level of community diversity was assessed using the following environmental indicators: the Simpson (evenness), Chao (richness) and Shannon coefficients. Сluster analysis was used to assess diversity between communities (beta diversity). The Dice coincidence index, which accounts only for the presence or absence of a taxon, was used as a similarity measure. It was found that the highest values for all three estimates were characteristic of communities obtained from the surface of the gills and the lowest values were observed in communities obtained from intestinal scrapings. The results of cluster analysis with the use of the principal component method showed that the intestinal microbiomes of the two pools had the greatest difference and the microbiomes of the fin surfaces had the smallest difference. Thus, the dependence of the degree of differences between microbiomes on the pool they were obtained from increased in the following order: fin surface communities – gill surface communities – intestinal communities. Microbiomes obtained from the surface organs of fish were more similar to each other and intestinal microbiomes were less.

MODERN STATUS AND PROSPECTS OF ARTIFICIAL BREEDING OF RARE, EXTINCTING FISH SPECIES FOR CONSERVATION OF BIODIVERSITY AND RESTORATION OF ABUNDANCE IN NATURAL WATER RESERVES OF THE ILE-BALKHASH BASIN

This article presents materials on the current state of the native ichthyofauna of the Ile-Balkhash basin, affected by large-scale acclimatization works. Four species of the ichthyofauna composition are listed in the Red Book of Kazakhstan: spike ( Acipenser nudiventris Lovetsky, 1828), Aral barbel ( Barbus brachycephalus brachycephalus Kessler, 1872), Balkhash marinka ( Schizothorax argentatus argentatus Kessler, 1874), Balkhash perch ( Perca schrenkii Kessler, 1874). Due to the ineffectiveness of fish conservation measures, including the prohibition for catching of these fish species, which are not found anywhere except in the Ile-Balkhash basin, it is necessary to impose artificial reproduction, changes in the Fishery Rules and organization of commercial rearing. The work is based on research materials of 2001-2018 conducted in Lake Balkhash, the delta and the lower reaches of the Ile and the Tokraun. The status of spike populations ( Acipenser nudiventris Lovetsky, 1828), Aral barbel ( Barbus brachycephalus brachycephalus Kessler, 1872), Balkhash marinka ( Schizothorax argentatus argentatus Kessler, 1874) and Balkhash perch ( Perca schrenkii Kessler, 1874). The main reasons preventing the maintenance of a high number of endangered species have been established: small area of natural spawning grounds, death of fry in linmeshing fishing gear, large-scale poaching (spike); deterioration of conditions for the natural reproduction, mass mortality of young fishes in the irrigation system (Aral barbel); total elimination and food competition with pike perch (Balkhash marinka, Balkhash perch). The prospects for preservation of rare and endangered fish species have been considered, recommendations for breeding and replenishing populations of species listed in the Red Book have been given: measures for artificial reproduction and prevention of juvenile death, creating favorable conditions for fattening and reducing the pressure of trophic competition. Without taking adequate measures for reducing the anthropogenic impact on natural resources, including ichthyofauna, the number of main commercial fish species will decrease, rare species of fish will die out.