Evaluation of genetic polymorphism of proteins in stellate sturgeon Acipenser stellatus (Pall) in aquaculture with reference to economically valuable traits

One of the main goals of sturgeon aquaculture is the restoration and renewal of wild populations of sturgeon fish in nature, which creates a tension between selective breeding with maintenance of valuable economic traits in a homozygous state and the need to conserve genetic diversity ensuring fitness in natural environments. It is generally assumed that important economic characteristics, such as body weight and size, growth rate, fecundity, etc., as well as fitness in fish, are associated with heterozygosity and genetic polymorphism of some key metabolic enzymes. It remains unclear whether aquaculture conditions can be as a whole selection factor in favor of certain allelic variants of these enzymes. To establish the relationship between some economic traits and enzymatic polymorphism, we studied the distribution of allelic variants of LDH-3, AAT-2, FGM, and Est enzymes in stellate sturgeon reared in aquaculture. We revealed a frequency bias of some allelic variants of the studied enzymes in a cohort of fish from the generation bred in aquaculture compared to the frequencies of those alleles in wild natural populations. Our study suggests that industrial breeding promotes selection in the direction of reducing size but increasing survival rates, which correlates with certain allelic variants.

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.

Genetic Diversity of Stellate Sturgeon in the Lower Danube River: The Impact of Habitat Contraction upon a Critically Endangered Population

One of the last wild populations of the critically endangered stellate sturgeon (Acipenser stellatus) survives in the Danube River. Limited knowledge about the genetic structure, ecology, and evolution of this species led to poor and inconsistent management decisions with an increased risk for species extinction in the wild. Here we show the results of genetic structure screening of the Danube River wild population over 12 years timespan. Our research does not bring evidence of population recovery. No genetic structuring was identified at the mitochondrial level concerning spawning migration timing, sampling locations, and developmental stages. Eleven maternal lineages were revealed based on restriction fragment lengths analysis of the D-loop region, with one haplotype as the most frequent. While this could be the result of a massive restocking activity using a reduced number of spawners, our data does not support it. The selection of mitochondrial haplotypes under the pressure of habitat contraction and the narrower range of temperature variation since dams’ construction on the river could explain the observed distribution. Several factors of managerial concern are discussed. Our results provide baseline data on the mtDNA diversity in a critically endangered species of exceptionally high socioeconomic and conservation interest.

Assessment of food intensity and growth rate young sevryuga (Acipenser stellatus Pallas, 1771) depending on from the terms of fishing of growing ponds

Artificial reproduction of sturgeon fish in the Volga-Caspian basin in modern conditions is the only real opportunity to replenish natural populations with juveniles, therefore, increasing its efficiency is the key to restoring the stocks of these relict fish species. Improving the technological processes of growing juvenile sturgeon fish, including the Caspian stellate sturgeon, the number of which has been rapidly decreasing in recent years, is one of the main tasks at present. We studied the conditions for growing stellate sturgeon larvae in the nursery ponds for artificial reproduction at different periods of their watering. It is known that the stocking of ponds with larvae that have switched to exogenous feeding occurs at the end of June or the beginning of July, this coincides with the time of maximum water heating in nursery ponds to extreme (26–28 °C) values and with a depletion of the food supply in them. Hydrobiological studies were carried out to assess the food supply in water bodies that were watered in the traditional (June 12–14) terms (control option) and earlier (May 28) 2 weeks earlier than usual (experimental option). In addition, the intensity of feeding and the growth rate of juvenile starred sturgeon in the indicated ponds was studied for 20–24 days. The results of the studies performed showed that the food supply in the experimental pond was higher, so the zooplankton was represented by four orders, the biomass on average ranged from 2,8 to 4,6 g/m³, and in the control variant, planktonic organisms were represented by three orders, total biomass from 0,3 to 2,5 g/m³. The same tendency can be traced for zoobenthos. The feeding intensity of stellate sturgeon fry reared in ponds of early watering had indicators in terms of the gastrointestinal tract filling index, fatness coefficient and growth rates higher than the juveniles kept in water bodies of traditional watering periods.

Age-related variability in the stellate sturgeon domestication in industrial conditions

Morphometric studies are fundamental in the domestication of new fish species. Despite the obvious dependence of the morphological parameters of fish on habitat conditions, they are currently used as the main criteria for the approval of breeding achievements, and a measure of the processes of domestication and selection. In this regard, we have begun work to study the variability of morphological characters in the process of domestication of stellate sturgeon (Asipenser stellatus, Pall) in a closed water supply. Researched sturgeon of Volga origin grown from caviar in artificial conditions in a closed water supply installation. At the first stage, 25 morphological parameters of stellate sturgeon underyearlings were studied. At the second stage, six years later, morphological studies were repeated in the same group of fish. Comparison of the average values of the indicators indicates the following trends in their change with the age of the fish: the relative length and height of the head, the rostrum (rr), and the diameter of the eye, the width of the mouth and the width of the break of the lower lip decrease; the indicators of the distance between the fins relative to the end of the snout and between themselves increase, the smallest and largest body height. At the same time, the most significant significant differences between underyearlings and six-year-olds were found in body height and head length. Similar changes are observed with age in most fish, including sturgeon. They are associated with the development of swimming muscles, physiological changes and demonstrate the expected biological age-related changes. The presented data on age-related changes in morphological parameters show the erroneousness of using sturgeon underyearlings as a control group for assessing uniformity and stability for distinctness.

The aquaculture of acipenseriformes. Part 5. Dunabe Basin and Middle East

The history and contemporary state of global aquaculture of sturgeons and paddlefish are reviewed. 5th part is devoted to sturgeon breeding in the basin of Black sea (without countries of former USSR reviewed earlier) аnd in the Middle East. Six species of sturgeon once migrated in the Danube River and Turkish rivers Yeşilırmak, Kızılirmak and Sakarya for spawning: anadromous beluga Huso huso, Russian sturgeon Acipenser gueldenstaedtii, stellate sturgeon A.stellatus, European sturgeon A. sturio and the river resident ship sturgeon A. nudiventris and sterlet A. ruthenus. Sturgeons had played an important role in the history Black sea fisheries, but due to overexploitation, followed by extensive river regulations and deterioration of water quality decrease in their populations has led most of them to the verge of extinction. During the 20th Century, world demand for sturgeon meat and caviar has inflated the economic value of sturgeons so Danube basin countries and Turkey develop commercial aquaculture and conservational programs. As result of protective measures the limited natural spawning of beluga, Russian and stellate sturgeons and sterlet is preserved in Danube. In Sakarya River last spawning population of stellate sturgeon exists. These species and Siberian sturgeon are important objects of commercial aquaculture in all countries of Black sea basin. The leaders of commercial sturgeon farming in this region are Bulgaria and Israel. The sturgeon aquaculture of Hungary and Turkey developed rapidly. Saudi Arabia and United Arab Emirates are important importers of caviar. Saudi Arabia is large consumer of caviar and UAE is one of main re-exporter of caviar. Both Arab countries develop own sturgeon aquaculture.