Valuable Fish Species Research Articles

Pacific ocean perch and Atka mackerel research in the Pacific waters of the Northern Kuril Islands and Eastern Kamchatka in February-April 2024

The aim: obtain data on the biology, distribution and abundance of the Pacific ocean perch, Atka mackerel, by-catch species, and monitor aquatic biological resources.The methods: in the course of specialized fishing, fishing information was collected and ichthyological work was carried out according to the generally accepted methodology.The newness: expeditionary work is a continuation of many years of scientific research on the state of commercial populations of valuable fish species in the western part of the Bering Sea and Eastern Kamchatka and the North Kuril Islands.Results: concentrations of Pacific perch were noted in the area of Cape Kamchatsky, Cape Kronotsky, and in the area of Shiashkotan and Onekotan islands. The largest catches were recorded at Cape Kronotsky (2.25–5 tons/hour of trawling). The average length of the beaked perch decreased from north to south from 39 cm to 37 cm, weight — from 868 g to 681 g. The main concentrations of the Atka mackerel were noted in the area of Cape Afrika and Cape Kamchatsky (the largest catches are 8–10 tons/hour of trawling), at Kronotsky (5–9 tons/hour trawling) and Shiashkotan Island (15–40 tons/hour trawling). The average length of the Atka mackerel was 38–39.6 cm with a weight of 635–752 g.The practical significance: the results of this work will be taken into account when developing and updating materials for forecasting the total allowable and recommended catch and recommendations for efficient fishing.

A chromosome-scale reference genome assembly for Triplophysa lixianensis

In this study, we constructed a chromosome-scale reference genome assembly for Lixian plateau loach, Triplophysa lixianensis, by integration of MGI short-read, PacBio HiFi long-read and Hi-C sequencing technologies. A 668-Mb haplotypic genome assembly was obtained for a female T. lixianensis, and 98.91% of the assembled sequences were anchored into 25 chromosomes. This assembly owned a moderate repeat content (35.63%) and an annotation of 23,774 protein-coding genes, among them 94.15% were predicted with functions. The assembled genome of T. lixianensis shared a good syntenic relationship with previously published data of its relative T. dalaica. Taken together, our genome data presented here provide a valuable genetic resource for in-depth evolutionary and functional studies, as well as molecular breeding and conservation of this valuable fish species to elevate its ecological and economical values.

Опыт формирования ремонтно-маточного стада шипа (Acipenser nudiventris) для целей воспроизводства на базе ТОО «Halyk Balyk» Алматинской области

In modern conditions due to the intense anthropogenic impact on the ecosystem, and accordingly on the habitats of valuable fish species, there is a landslide reduction in spawning populations of thorn in the Ili-Balkhash basin. The issue of preserving this species is discussed through the formation of repair and breeding herds from “wild” individuals, domestication in controlled conditions of fish farms. Only under controlled conditions are there opportunities for the formation of productive herds of endangered fish species. The production facilities of Halyk Balyk LLP were used to carry out work on the reproduction of young thorns and the formation of repair and brood stock of thorns. Throughout the entire period of thorn cultivation, direct-flow water supply from an artesian well was used in the pools of Nalyk Balyk LLP. The water temperature in the pools ranged from 15.0 to 15.50 °C. To increase the immune status in order to prevent stress, courses of vitamin C, B vitamins, and viusid - vet feed additives were regularly administered as needed. The use of such a feeding scheme allows to increase the growth rate of fish, increases the survival rate of fish and improves their physiological condition, fish become more resilient. The adaptation of “wild” individuals of the thorn takes place in a shorter time. Based on the determination of the growth and dynamics of the mass of adaptable individuals, it was found that the habituation to new conditions and artificial feeds is slow, only in the second month the fish begins to eat fruitfully. The survival rates of the domesticated thorn for the entire growing period were 100%.

Содержание химических элементов в костистых лучах плавников Acipenser gueldenstaedtii (Brandt, 1833)

One of the reasons for the decline in the number of sturgeon fish species is the complex ecological situation in the Volga-Caspian basin. Changes in the hydrochemical composition of the Volga-Caspian basin water are accompanied by critical disturbances in the microelement balance of the fish organism and lead to irreversible pathological consequences in the populations of valuable fish species. In order to preserve the population and monitor the condition of sturgeon fish species, a detailed study of the microelement composition of their organs and tissues is necessary. The concentration of chemical elements in the bony rays of the fins of Russian sturgeon Acipenser gueldenstaedtii (Brandt, 1833) of different sexes and age composition (3-10 years) was determined using the atomic absorption method according to GOST 30178-96. Iron, copper, manganese, zinc, nickel, cobalt, chromium, lead, cadmium were determined in each sample. It is noted that all nine studied metals are able to accumulate in sturgeon bone rays to one degree or another. Iron in sturgeon bone rays was present in large quantities relative to other chemical elements. Lead occupied the second place in terms of content in the rays, followed by zinc and cobalt in descending order, and cadmium was found in the lowest concentrations. Copper, zinc, and manganese were shown to have higher metal concentrations in the rays of males, and nickel, chromium, cobalt, lead, and cadmium in the rays of female Russian sturgeon. The differences revealed between the average iron concentrations in the studied organs of females and males of all studied age groups are statistically insignificant. It was noted that with increasing age, weight, and length, the metal content in the bone rays of both males and females increased.

Влияние пирролидиновых производных 2,6-ди-трет-бутилфенола на супероксид- и пероксид водорода-утилизирующую активность спермы сибирского осетра

The effect of (3.5-di-tert-butyl-4-hydroxyphenyl)-pyrrolidine-2-carboxylic acid derivatives on the ability of Siberian sturgeon (Acipenser baerii, Brandt, 1869) sperm to utilize superoxide anion radical (O2–•) generated in a model system of adrenaline oxidation in an alkaline medium, as well as exogenous hydrogen peroxide (H2O2) before and after freezing at liquid nitrogen temperature for 3 days was studied. The study of this activity of phenolic derivatives was carried out in comparison with the reference antioxidant Trolox, a water-soluble analogue of vitamin E. When phenolic derivatives were added at a concentration of 0.1 mM to the basic Stein cryomedium containing 12.5% egg yolk, 12.5% DMSO, 5 mM KCl, 130 mM NaCl, 20 mM NaHCO3 and 5.5 mM glucose, a multidirectional effect of the compounds on the ability of Siberian sturgeon sperm to utilize superoxide anion radical and hydrogen peroxide before and after the freezing-defrosting process was established. The studied compounds increase the H2O2-utilizing activity of reproductive cells, while reducing their superoxide-utilizing activity. Pyrrolidine derivatives of phenol were found to be more effective in stimulating the H2O2-utilizing activity of defrosted sperm of the Siberian sturgeon than Trolox. A decrease in the rate of O2– • and H2O2 utilization by fish sperm was found after cryopreservation in the control and in the presence of (3.5-di-tert-butyl-4-hydroxyphenyl)-pyrrolidine-2-carboxylic acid derivatives. A protective effect of new phenolic derivatives on the enzymatic link of antioxidant protection of Siberian sturgeon sperm during cryopreservation was shown. The obtained results indicate the prospects for further studies of the protective activity of (3.5-di-tert-butyl-4-hydroxyphenyl)-pyrrolidine-2-carboxylic acid derivatives in the process of cryopreservation of reproductive cells of rare, endangered and commercially valuable fish species.

Aspects of Growth, Diet, and Reproduction of <i>Oreochromis niloticus</i> (Linnaeus, 1758) in a Hypertrophic Milieu, the Municipal Lake of Yaoundé, Cameroon

The Nile tilapia, <i>Oreochromis niloticus</i>, is a highly valued fish species in Africa for subsistence and commercial purposes. However, overfishing activities in non-supervised lakes or reservoirs threaten its availability. In the view of contributing to the database on the life history traits of this species in Cameroon and supporting its sustainable management, the present study investigated the growth patterns, food preferences, and reproductive aspects of <i>O. niloticus</i> in a hypertrophic milieu, the Yaoundé Municipal Lake, from May to October 2018. Fish specimens were sampled, measured, weighed, and sexed. The digestive tract of each specimen and the females’ gonads were collected. The intestines were measured, and the stomach contents were identified. The females’ reproductive aspects were determined. Overall, 101 specimens were collected and distributed among 48 (47.5%) males and 53 (52.5%) females, with a sex ratio of 1: 1.1. In this hypoxic (1.35 ± 0.4 mg/L) and highly conductive (210.5 ± 56.9 µS/cm) milieu, <i>O. niloticus</i> displayed a relatively good condition (<i>Kn</i> > 1) throughout the sampling period and negative allometric growth patterns for both sexes (<i>b </i>< 3; <i>p</i> < 0.001). Materials from plant origin were the preferred prey types, with an index of relative importance (IRI) of 78.20%; meanwhile, mud and materials from animal origin were secondary prey items (IRI: 13 ‒ 17%). The relative gut length (RGL) value above 3.0 and the foraging activity on detritus suggest that <i>O. niloticus</i> has an herbivorous or detritivorous dietary habit and is a bottom-feeder. Female length at first maturity (L<sub>50</sub>) was 17 cm. Their gonado-somatic index (GSI) showed sexual activity throughout the whole sampling period, with the peak spawning phase happening in August. The absolute fecundity of gravid females varied between 316 and 1816 oocytes (942 ± 430 oocytes), and the relative fecundity ranged from 1–5 oocytes/gram of body weight (3 ±1 oocytes/g). The results highlight the performance of the Nile tilapia in this ecosystem and provide information for its sustainable use and improvement of fish culture.

Genome sequencing and transcriptome analysis provide an insight into the hypoxia resistance of Channa asiatica

Channa asiatica is an economically valuable fish species and excellent model for studying hypoxic tolerance. However, the underlying genetic and molecular mechanisms are poorly understood. In this study, we assembled a high-quality C. asiatica genome (23 chromosomes, totaling 722 Mb) using a combination of Illumina short-read, PacBio long-read, and Hi-C sequencing. Repetitive elements accounted for 28.39%of the C. asiatica genome, and 23,949 protein-coding genes were predicted, with 96.63 % of these functionally annotated. Moreover, a comparative genomic analysis of 12 fish genomes showed that gene families associated with oxygen binding and transport were expanded in C. asiatica. In addition, transcriptome analysis revealed that multiple oxidative stress pathways were activated when C. asiatica was exposed to air. In conclusion, this study provided high-quality genome assembly and transcriptome data, both serving as critical resources for researching the genetic basis of hypoxic tolerance in C. asiatica.

Establishment and characterization of SSI cell line from Sebastes schlegelii intestine for investigating the immune response to Pathogenic Bacteria

As a commercially valuable fish species, Sebastes schlegelii faces threats from pathogenic bacteria like Edwardsiella piscicida during aquaculture. The global host range of E. piscicida encompasses various species, yet its pathogenic mechanism remains incompletely elucidated. Cell lines offer invaluable in vitro resources for studying the pathogen pathogenicity. Here, we established and characterized a cell line derived from the intestinal tissue of the S. schlegelii, designated as SSI. SSI has undergone continuous subculturing for over 80 passages, demonstrating robust growth in DMEM supplemented with 10%–20% FBS and 20 μM HEPES at 24°C. Karyotype analysis and 18S rRNA amplification confirm its origin. SSI exhibits high transfection efficiency for exogenous DNA, making it suitable for gene expression and intestinal function analysis. E. piscicida infects SSI cells at low densities without inducing morphological changes within 6 h of infection, suggesting the potential of SSI as an in vitro model for studying E. piscicida pathogenicity. This cell line provides a valuable tool for investigating mucosal immunity and E. piscicida pathogenic mechanisms in marine fish.

ERMƏNİSTANIN AZƏRBAYCANA QARŞI EKOLOJİ TERRORU

Since 1988, 20% of Azerbaijan's lands have been occupied as a result of the war waged by Armenia to pursue its territorial claims against Azerbaijan. After a long occupation, during the 44-day Patriotic War and 24-hour local anti-terrorist operations, our lands, which had been in the hands of the enemy for almost 30 years, were liberated by our brave Army. However, in the territories we liberated from occupation, the enemy left behind ruins and an environmental disaster. For almost 30 years, Armenia deliberately tried to destroy our nature, carried out environmental terrorism against Azerbaijan, spontaneously exploited natural resources, including our occupied territories, polluted drinking water reservoirs with industrial waste, and disrupted the ecological balance of the environment. During the occupation, the enemy committed the great¬est acts of vandalism on our lands; the occupying forces destroyed forests, national parks, nature reserves, valuable trees and other rare examples of biodiversity. The rivers that are the source of Azerbaijan's drinking water are contaminated with chemical, biologi¬cal and other radioactive waste flowing from the territory of Armenia. Over the past years, contamination of water sources flowing from the occupied territories has led to the death of valuable fish species and the depletion of fish stocks. 7 ecologically important relic lakes and 10 reservoirs in the liberated territories of Azerbaijan were subject to serious anthropogenic impact from the occupying Armenia.

The use of aquatic bioresources as a factor in ensuring Ukraine’s food security: legal aspects

The article is dedicated to the study of the legal aspects of using aquatic bioresources in Ukraine and the impact of their usage on ensuring the country’s food security. It is argued that the issue of proper legal regulation of the use of aquatic bioresources is becoming increasingly relevant today. Attention is given to both legislative and scientific approaches to the issue of legal regulation of Ukraine’s food security. The necessity of adopting a separate law titled «On the Fundamentals of Food Security of Ukraine» is emphasized. It is noted that the state’s food policy should aim for the highest degree of self-sufficiency, as the quality and quantity of consumed food products directly impact the nation’s health, life expectancy, work capacity, and intellectual potential. The article examines the legal grounds for the usage of aquatic bioresources. The impact of the fishing industry on ensuring Ukraine’s food security is analyzed, with the conclusion drawn that the country’s food security largely depends on the state of aquatic bioresource usage. The level of fish consumption and its processed products serves as an indicator of the population’s food security, which should be maintained at a level conducive to physiological needs. It is stressed that the development of the fishing industry is one of the most important tasks for ensuring the post-war recovery of the country. The article identifies aquatic bioresources as a strategic state food reserve in the current context. The artificial reproduction of valuable fish species is aimed at both supporting aquatic ecosystems and building industrial stocks. The author asserts that today, food security is a condition for maintaining the state’s sovereignty, supporting high levels of public health, and developing the country’s economy. Emphasis is placed on the fact that the use of aquatic bioresources is crucial for the country in terms of ensuring food security, improving economic conditions, saturating the domestic market with quality food products, increasing employment and welfare, as well as preserving biodiversity and effectively using water and hydrobiological resources.

Assessing the potential ecological and human health risks of trace metal pollution in surface water, sediment, and commercially valuable fish species in the Pashur River, Bangladesh.

This research examines the contamination levels in the Pashur River in Bangladesh stemming from trace metal discharge originating from the Mongla seaport and various industrial outlets. It delves into both ecological risks and potential health hazards for humans consuming fish carrying accumulated trace metals. The research employed atomic absorption spectrometry to measure the concentrations of chromium (Cr), arsenic (As), manganese (Mn), copper (Cu), zinc (Zn), nickel (Ni), lead (Pb), and cadmium (Cd) in surface water, sediment, and fish samples. Target hazard quotient (THQ) and carcinogenic risks were calculated to determine the human health risk caused by the consumption of these targeted fish species. An RI value of 42.89 indicates that the collective presence of trace metals in sediment poses significant ecological risks to the study area. Although the majority of trace metals present in sediment are categorized under class 1 (ranging from unpolluted to moderately polluted) based on the Igeo values, Cd is classified under class 2, signifying a moderate level of pollution. Significantly, THQ values surpass the threshold of 1 for Cr and As, indicating potential health risks associated with the consumption of specific fish species. Among the trace metals analyzed, Ni demonstrates the highest cancer risk (CR) value, at 5.78 × 103, indicating a notable cancer risk associated with the consumption of targeted fish. Recommendations include the strict enforcement of waste disposal policies to mitigate anthropogenic discharge and safeguard the river from further pollution.

Fisheries and biological characteristics and state of stocks of the main commercial fish species in Beloye Lake

The current composition of the ichthyofauna and the importance for fisheries of the main fish species in Beloye Lake (Vologda Region) is described in the article based on research materials from 2018 – 2022. The biological features and commercial use of twelve most valuable fish species are summarized as result of the composition of industrial and research catches studies. The size and age composition of catches, the age of puberty, the timing and conditions of spawning, and the feeding patterns of fishes were studied. The influence of net fishing gear with different mesh spacing on commercial fish populations and the magnitude of nets fishing productivity (fishing effort) were studied for the first time. The role of the most important fish species for industrial fisheries in Beloye Lake was assessed.

Discriminating the origin of fish from closely related water bodies by combining NMR spectroscopy with statistical analysis and machine learning

Pikeperch, perch and bream are among the most traded and valued fish species in North-Eastern Europe. Therefore, it is necessary to be able to distinguish fish from different lakes and coastal sea regions to ensure a good traceability of products in the fish market and to protect both consumers and fish stocks. Untargeted metabolomics using nuclear magnetic resonance (NMR) spectroscopy is a suitable tool for this purpose. It is an established method for determining various properties of biological and living systems, such as health, origin, type, etc. Statistical methods including principal component analysis (PCA) and linear discriminant analysis (LDA) are typically applied to NMR data to correlate spectra with a particular research question.Herein we examine fish from three closely related water bodies and demonstrate that reliable determination of the water body that a particular fish originates from by traditional statistical analysis (PCA and LDA) of fish NMR spectra is not possible. In contrast, determining the fish species is possible. We proceed to show that machine learning methods perform better and that a combination of statistical analysis (LDA) and random forest (RF), a supervised machine learning technique, allows reliable determination of the originating water body, while being also tolerant to seasonal variations. This is an improvement over prior work, which has dealt with more clearly distinguished origins of fish. Exceptional accuracy was achieved in correctly assigning fish to their origin even in a scenario where two of the water bodies are connected by a river through which the fish are known to migrate. Since determining the origin of fish is important in environmental protection, we recommend following up this approach and using it as the basis of a robust tool for environmental protection and other monitoring purposes.

Study on the relationship between economic input growth in Marine protected areas and environmental governance in the North Pacific Coast of Costa Rica: Based on reef fish assemblages

Reef fish communities under fishing pressure often experience reduced biomass, abundance, and altered size structure. The establishment of marine protected areas (MPAs) can help mitigate these declines. However, the success of MPAs, especially in developing countries with financial and socioeconomic challenges, largely hinges on effective enforcement. This study utilized underwater visual surveys (UVS) and baited remote underwater video stations (BRUVS) to evaluate population density, size distribution, and biomass of both economically valuable (e.g., target and ornamental species) and ecologically important (e.g., small/large predators and herbivores) fish groups within and outside a no-take MPA on the northern Pacific coast of Costa Rica.The results indicated that protective measures did not significantly affect the biomass of economically valuable fish species. However, there were notable differences in fish abundance and size distribution between no-take zones (where fishing is prohibited) and open-fishing zones. This suggests that, despite potential illegal fishing activities within the MPA, certain fish community components benefit from the protective measures.Specifically, herbivores and ornamental fish, which are often targeted by artisanal compressor fishing and the aquarium trade, exhibited higher biomass and abundance levels within the MPA. Additionally, significant shark species such as Galeocerdo cuvier, Carcharhinus leucas, and Carcharhinus limbatus were exclusively found within the MPA.The study also highlighted the crucial role of habitat quality, particularly high coral cover, in enhancing the biomass of ornamental fish.This research contributes to the growing body of evidence that MPAs, even with limited enforcement, consistently offer ecological benefits for reef fish communities

Evaluation of the safety, immunogenicity and protective effect of an attenuated Pseudomonas plecoglossicida strain ΔgacS as the live vaccine for the large yellow croaker (Larimichthys crocea)

Pseudomonas plecoglossicida is one of most important pathogenic bacterial species in large yellow croaker and several other commercially valuable fish species. In our previous study, a GacS deficient mutant (ΔgacS) was constructed and its virulence showed substantially attenuated. In present study, the safety, immunogenicity and protective effect of the ΔgacS were evaluated in large yellow croaker as a live-attenuated vaccine candidate. It was shown that the ΔgacS strain exhibited good safety to large yellow croaker and there was no mortality or clinical symptoms observed in all fish that infected by ΔgacS strain with the doses range from 2 × 105～107 CFU per fish via intraperitoneal injection (IP) or immersion (IM), and almost all bacteria were cleaned up in the spleen of the fish at 14-day post infection. Specific antibodies could be detected at 7-day and 14-day post infection by direct agglutination method, and the valences of antibodies and bactericidal activities of the serum were significant increased with vaccination doses and vaccination time. Moreover, the expressions of some molecules and cytokines involved in specific immune responses were detected in the ΔgacS strain immunization group and control group. After challenged by the wild-type (WT) strain XSDHY-P, the relative percentage survival (RPS) showed highly correlated with the immunized dosage regardless of vaccination methods. It showed that the RPS of the IP groups were 39.47 %, 57.89 %, 71.05 % with the immune dosage in a descending order, respectively, and the RPS of the IM groups were 26.31 %, 36.84 %, 76.31 % with the immune dosage in a descending order, respectively. In summary, the ΔgacS strain exhibited safety and good protective effect to large yellow croaker and was a potential live vaccine candidate.

Occurrence of microplastics in commercial fish species from the Ethiopian rift valley's Lake Hawassa, Ethiopia.

Microplastics (MPs) have recently been detected as emergent pollutants in the Ethiopian rift valley lakes located close to rapidly expanding towns. We provide the first study of MPs ingestion of commercial fish species from Lake Hawassa, Ethiopia: Catfish (Clarias gariepinus) and Nile Tilapia (Oreochromis niloticus). A total of 60 individual fish species was collected from three sampling sites of lake Hawassa in October 2020. Across all sampling sites, there was a significant difference in ingested MPs between benthic omnivore catfish and pelagic phytoplanktivorous Tilapia (χ2 = 15.864, p < 0.001). The most common size of ingested MPs (84.6%) was 0.5-1mm, with fragments (59.5%) dominating, followed by fibers (25.4%). On average, 4.03 ± 1.33 MPs with sizes ranging between 60μm and 10.53mm were detected per individual. White and yellow MPs were particularly numerous, accounting for 36.8% and 26.4% of the total, respectively. Because Lake Hawassa's fishery is so significant, the potential impact of MP pollution on the lake biota in general, and economically valuable fish species in particular, deserves attention, additional research, and, if possible, early mitigation.

Physiological and biochemical studies of young sterlet sturgeon (Acipenser ruthenus L.) in the lower reaches of the Volga river

In conditions of a decrease in the number of rolled sturgeon larvae in the lower reaches of the Volga River, an urgent issue is the study of the physiological and biochemical parameters of the fish organism. The purpose of this work is to conduct physiological and biochemical studies of juvenile sterlet (Acipenser ruthenus L, 1758). The study of fish was carried out using the methods of classical histology and biochemistry. The degree of damage to the gills and liver was assessed on a scale from 1 to 5 points. The content of total lipids and water-soluble protein in the muscle tissue of sterlet fingerlings was studied as biochemical parameters. The morphological picture of the gills of 80% of the fish corresponded to a weakly pronounced character of changes (2 points), while in others it was characterized by the presence of a borderline state between weakly pronounced changes and moderate injuries (2–3 points). Six types of disorders were found in the gills: hyperplasia of the respiratory epithelium of lamellae, dilation of the blood vessel of the filament, goblet-shaped swellings of the apical part of the filament, invasions, expansion of the apical part of the lamellae, proliferation of connective tissue of lamellae. In the liver of 80% of fish, a borderline state was recorded between mild changes and moderate damage (2–3 points), in 13.3% of individuals the liver had mild damage (2 points), in 6.7% there were medium damage (3 points). Four types of disorders were found in the liver of juvenile sterlet: fullness of the liver capillaries, pronounced venous fullness, cavities, capillary dilation. In the muscle tissue of fingerlings, the concentrations of total lipids were in the range of 1.39–5.28%, and water-soluble protein — 45.59–57.97 mg/g. The study of the physiological and biochemical parameters of juvenile sturgeon in the lower reaches of the Volga River is very important for the biology of the species and monitoring the natural reproduction of these valuable fish species.

Genetic Analysis of Three Geographically Secluded Populations of Nile TilapiaOreochromis niloticus(Cichlidae)

AbstractNile tilapiaOreochromis niloticusis one of the most important fishery resources and a valuable fish species for aquaculture programmes. It is found in almost all waters and is widely dispersed. Several natural populations of this species have been impacted by genetic pollution despite their significant economic relevance. Understanding population structure is a crucial first step in protecting this species in its native habitats as well as in choosing which wild stocks to use in hatchery initiatives. To demonstrate the genetic-population structure of this species, genetic differences among three geographically secluded populations ofO. niloticuswere investigated utilizing mitochondrial DNA cytochrome b gene sequences. The results were used to estimate the levels of genetic variability within and among the populations. The 56 cyt b (821 bp) sequences analysis revealed 21 haplotypes, with a nucleotide diversity of 0.0510 and a haplotype diversity of 0.881. In each of the populations, seven (7) singleton variable sites and 19 informative-parsimony sites, genetic diversity could be identified and few population haplotypes were found, indicating a minor genetic distinction between them. For the purpose of conservation and/or Nile tilapia breeding programmes, this information would assist in choosing the fish populations that maintain greater genetic variation inO. niloticus.

Improved breeding and seed production of climbing perch (Anabas testudineus) in controlled tanks and cage systems

The climbing perch (Anabas testudineus) is a valuable fish species with significant potential for aquaculture. However, a low survival rate was observed at its early development stages, requiring an optimized protocol for sustainable aquaculture production. This paper presents an improved breeding and seed production technology for climbing perch. Mature climbing perch were induced to spawn using salmon gonadotropin-releasing hormone analog (sGnRHa) at a dose of 30 µg/kg-1 body weight of the breeder. The female broodfish spawn 9–10 hours after hormone injection. Developmental stages were defined based on the morphological features of the embryos from the first cleavage to the hatching stage. The first cleavage began at approximately 18–20 minutes after fertilization. Newly hatched larvae were observed within 18–20 h at 30°C, having an average larval size of 0.389±0.042 mm (total length). Successful breeding entails a selection of suitable algal species, an optimal aquaculture environment, regular feeding rates, consistent monitoring of larval development, and effective management of water quality. Survival rates from the larval stage to fry were achieved at 84.69% and 77.60%, respectively, while the survival rate to the fingerlings stage was 72.51%. Therefore, by implementing an optimized protocol, aquaculture practitioners can maximize the production potential of climbing perch while ensuring sustainable cultivation practices. The findings from this research contribute to the advancement of climbing perch aquaculture by providing valuable insights for the successful cultivation and increased economic profitability of A. testudineus species in hatchery productions.

Развитие интеграционных формирований рыбоводных хозяйств в Белгородской области

Modern commercial fish farming in Russia is mainly represented by small enterprises. However, in the Central Federal District, and above all in the Belgorod Region, objective conditions have now been created that allow for the processes of concentration of production (with its simultaneous specialization) on the basis of the creation of new management and production structures (corporate associations), taking into account regional peculiarities of production placement and cooperative relationships. There are such favorable conditions in commercial fish farming in the Belgorod region. Being in favorable natural and climatic conditions and using modern biotechnics and fish growing technology, favorable opportunities have developed in the Belgorod regions for the introduction of a cluster production system for the cultivation of high–value fish species (sturgeon, salmon). It is important to create well-managed companies with the participation of heads of local authorities and qualified specialists.