Structure of poaching sturgeon species in the Irtysh River in 2013-2020 (according to ichthyologic examinations)

The study was carried out on the basis of the analysis of poaching sturgeon species in the lower reaches of the Irtysh River (the Tyumen region and Khanty-Mansi Autonomous Okrug), according to the results of forensic ichthyologic examinations over the period from 2013 to 2020. The size and weight ratio of Siberian sturgeon and sterlet in catches, the average weight of one fish species, the number of examinations performed, as well as the dynamics of these indicators for the considered time period were evaluated. As a result of the analysis performed, there has been seen an upward trend in the number of expert examinations (from 10 in 2013 to 25 in 2020). Among sturgeon species sterlet dominates in size, with the exception the period of 2017-2018. There has been stated the dynamics of increasing mass of Siberian sturgeon and, accordingly, a decrease for sterlet, with the average share of sturgeon to be less 50%. The average mass of a Siberian sturgeon species has increased from 0.8 to 1.2 kg, as well as a positive trend for the above period is noted when analyzing the total mass of sturgeon species during yearly examinations. Body mass of poached sterlet species hasn’t increased over the 8-year period, and its average value made 0.11–0.13 kg. Over the investigated period the number of forensic ichthyologic examinations has increased, the average mass growth dynamics in a Siberian sturgeon species has been stated, with predominating of immature species in both of sterlet and Siberian sturgeon catches.

Interspecific hybridization in natural sturgeon populations of the Eastern Black Sea: the consequence of drastic population decline?

The eastern part of the Black Sea and its tributaries are suitable habitats for several sturgeon species, among which Acipenser gueldenstaedtii, A. stellatus, A. nudiventris, A. persicus, A. sturio, and H. huso are well documented. However, different threats have led these species to a dramatic decline, all of them are currently listed as Critically Endangered, and some Locally Extinct, in that area. We tested 94 wild sturgeon samples from the Black Sea and Rioni River by analyzing the mitochondrial Control Region and nuclear markers for hybrid identification. The data analyses (1) assessed mitochondrial diversity among samples, (2) identified their species, as well as (3) indicated instances of hybridization. The data collected, besides confirming a sharp decrease of catches of Beluga and Stellate sturgeon in recent years, also revealed four juvenile hybrids between Russian and Stellate sturgeon, providing the first evidence of natural interspecific hybridization in the Rioni. The present communication raises concerns about the status of sturgeon species in this area and underlines the urgent need for conservation programs to restore self-sustaining populations.

Living Fossils: Sturgeon of the San Francisco Estuary

Sturgeon are fish that are considered living fossils. Their ancestors date back over 200 million years, to the same time as dinosaurs. These fish can grow taller than humans (over 2 m), weigh over 160 kg, and live as long as humans. Sturgeon species have special adaptations, such as a vacuum-like mouth and body armor called scutes. There are 27 species of sturgeon worldwide. Two species, green and white sturgeon, are native to California, USA, and are some of the largest animals in San Francisco Bay. Sturgeon populations have declined due to habitat loss, water management, overfishing, poaching, pollution, and climate change. Sturgeon cannot jump over barriers like salmon can, so structures like dams that block water also block sturgeon from reaching their natural spawning habitat farther upstream in the river. Scientists are using new technologies to monitor sturgeon populations and discover the unique behaviors of these dinosaur-era fish in California’s rivers and estuaries.

SANITARY AND ECOLOGICAL IMPORTANCE OF BACTERIA OF THE GENUS ACINETOBACTER ISOLATED FROM WATER AND FISH IN VOLGA DELTA

The article highlights the study of the sanitary and ecological features of acinetobac-teria,which were isolated from the water and fish in the Volga Delta in the period from 1987 up to 2010. Today, these bacteria are among the most dangerous pathogens for people, especially in hospitals. They can exist in hydroecosystems and interact with aquatic biota. There were analyzed 96 beluga species; 295 sturgeon species; 217 stellate sturgeon species; 50 sterlet species; 173 carp species; 447 zander species; 638 water samples in the fishing areas. There were examined the fish, parenchymal organs, intestines, gills, blood, gonads (in sturgeon), and muscle tissues. Pathogenicity factors were taken into account: growth at 37°C, fermentation of hemolysin, protease, lecithinase, catalase; viability in 3.0; 7.0; 10.0% broth with NaCl. It is shown that the occurrence of Acinetobacter in water ranged from 3.0 to 16.7%; in fish-from 4.6 to 10.5% of samples of the entire isolated microflora. Inferior to the dominant enterobacteria and aeromonads, acinetobacteria isolated from water and fish had all the analyzed pathogenicity factors, especially catalase activity. In combination with halophilicity, these bacteria can be preserved in fish when stored frozen and as salted fish products.

COEFFICIENTS OF ACCUMULATING CHEMICAL ELEMENTS IN ORGANS AND TISSUES OF RUSSIAN (ACIPENSER GUELDENSTAEDTII, BRANDT, 1833) AND PERSIAN (ACIPENSER PERSICUS, BORODIN, 1897) STURGEONS OF CASPIAN SEA

The article is focused on the possible ways of accumulating chemical elements (zinc, copper, chromium, nickel, lead, mercury) in the organs of aquatic organisms. In the course of the study, the coefficients of accumulating the chemical elements in the organs and tissues were calculated for the Russian (Acipenser gueldenstaedtii, Brandt, 1833) and Persian sturgeons (Acipenser persicus, Borodin, 1897) relative to the water of the northwestern part of the Caspian Sea, bottom sediments and the main objects of their food (Khvalyn goby (Neogobius caspius), Sandpiper goby (Neogobius fluviatilis), Caspian goblin (Benthophilus microcephalus), roach (Rutilus rutilus caspicus)). The studies were carried out according to the standard method of atomic absorption spectrometry. It is shown that the main source of accumulating the studied chemical elements in the organs and tissues of the Russian and Persian sturgeons is the water of the northwestern part of the Caspian Sea. It was found that the bottom sediments of the Caspian Sea act as an additional source of zinc and mercury found in the liver and kidneys of sturgeon species. Based on the calculated accumulation coefficients of chemical elements, there was revealed a predominantly alimentary nature of accumulating copper, nickel and mercury in the organs of both sturgeon species.

Morphofunctional assessment of domesticated and aquacultured beluga females

In the early 80-ies of the last century, there was a sharp decline in the population of the Caspian beluga in Russia. Its fishing was prohibited, except for catching for reproduction and scientific purposes. In the practice of sturgeon breeding, the method of repeated use of sturgeon females and males by obtaining sexual products in vivo, as well as growing breeders in artificial conditions, has become widely put into practice. Against the background of an acute shortage of wild breeders of this sturgeon species, in recent years, the main way to form sturgeon broodstock in the conditions of the Lower Volga region is domestication. However, in recent years, the catches of wild beluga females in the fishing areas of the Lower Volga are estimated as single specimens. The article studies the fish-breeding, biological and physiological parameters of domesticated and aquaculture-bred beluga females. The reproductive function of domesticated and artificially raised beluga females is evaluated. Some proposals for the intensification and priority areas of artificial reproduction in order to replenish natural populations are presented.

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.