Artificial Reproduction Research Articles

Using transcriptome analysis to investigate the induction of vitellogenesis in female Japanese eels (Anguilla japonica).

Using transcriptome analysis to investigate the induction of vitellogenesis in female Japanese eels (Anguilla japonica).

Artificial Fertilization Techniques in Bronze Featherback (Notopterus notopterus): First Report and Preliminary Findings

The Java-native bronze featherback (Belida Jawa), Notopterus notopterus, has been designated as a protected species under limited protection status by the Decree of the Minister of Maritime Affairs and Fisheries of Indonesia No. 83 of 2024, with captive breeding efforts undertaken for conservation and aquaculture to meet increasing consumer demand. This study provides a preliminary evaluation of artificial fertilization techniques in N. notopterus, focusing on hormone-induced spawning using Ovaprim™. The objective was to determine the effectiveness of hormone injection, optimal egg stripping timing, and hatching success under controlled water quality conditions. Two female broodstock received different dosages of Ovaprim™, and successful egg stripping was conducted after a 41-hour latency period. Fertilization rates of 30% and 11.23% were observed for the first and second females, respectively; however, hatching success remained extremely low at 0.52% for the first female, with no larvae hatching from the second. Despite maintaining water quality parameters such as temperature, pH, conductivity, and total dissolved solids within acceptable limits, the poor hatching rate suggests that additional factors, including ammonia concentration and dissolved oxygen levels, may have impacted embryonic development. This study establishes a foundational basis for artificial reproduction in N. notopterus, emphasizing the need for further research to optimize hormone protocols, sperm viability, and environmental conditions. These findings contribute to the advancement of aquaculture strategies for the conservation and sustainable management of this ecologically important species.

Карась золотий (Карась звичайний) (Carassius carassius Linnaeus, 1758). Тематична бібліографія

Purpose. To create a thematic bibliographic list of publications, which highlight the issues of natural and artificial reproduction as well as the harvest of crucian carp in the context of its vulnerability as one of the Red Book fish species in Ukraine, the results of studies of its population, genetic, ecological, physiological, biochemical, immunological and other characteristics. Methods. Systemic and selective methods were applied in the process of the systematic search. The bibliographic core have been consisted of scientific publications (monographs, conference proceedings, articles from collections of scientific works and periodicals) in mainly Ukrainian and English from the fund of the Institute of Fisheries NAAS Scientific Library, as well as resources available to its users. Results. There was composed a thematic list of publications with a total quantity of 160 sources covering the time interval from 1975 to 2025, and outlining issues regarding the reproduction, rearing, and harvest of the crucian carp (Carassius carassius L., 1758) as one of the species listed in the Red Book of Ukraine with the conservation status of vulnerable; in addition, they include the results of population, morphological, genetic, physiological, biochemical and other studies of crucian carp at various stages of ontogenesis and different living conditions. The literary sources were arranged in alphabetical order by author or title, and described according to DSTU 8302:2015 “Information and documentation. Bibliographic reference. General principles and rules of composition”, with the amendments (code UKND 01.140.40), as well as in accordance with the requirements of APA style — international standard of references. Practical value. The list may be useful for scientists, specialists, professors, and students whose area of interests includes studies of Red Book fish species, as well as productive, biological, population, genetic, ecological and other characteristics of cyprinids, in particular the crucian carp. Keywords: crucian carp Carassius carassius (Linnaeus, 1758), Red Book fish species, hybridization, breeding, pisciculture, population research, genetic studies, ichthyopathological research, ecological studies.

Генетична мінливість Acipenser baerii (Brandt, 1869) за білковим поліморфізмом у процесі доместикації в індустріальній аквакультурі

Purpose. To investigate the variability of the genetic structure of brood Siberian sturgeon by protein system loci during domestication under conditions of intensive aquaculture. Methodology. The study of polymorphism of protein systems was carried out using polyacrylamide gel electrophoresis. To assess the genetic structure of the Siberian sturgeon group, we used the blood serum age-5-6 fish (n=30) grown using intensive technology in floating cages in the climatic conditions of the Forest-Steppe of Ukraine. We determined the distribution of allelic and genotypic frequencies at the transferrin (TF), albumin (ALB) and esterase (Est-1, Est-2, 3.1.1.1) loci. During artificial reproduction and subsequent cultivation of Siberian sturgeon, the main productive parameters were determined and abiotic environmental factors were analysed using generally accepted methods. Statistical processing of the obtained data was carried out using common methodological techniques. Findings. Under favorable environmental conditions, high growth and survival rates of fish were observed at all stages of cultivation with positive dynamics of the development of their reproductive system. The genetic structure of a group of Siberian sturgeon individuals with an average weight of 3.60±0.11 kg was characterized by a high level of heterozygosity (94.2%). The value of Wright’s fixation index (FIS) varied in the range from -0.346 (at the ALB locus) to -0.741 (at the Est-2 locus) with a mean value of -0.491. A negative value of the fixation index (inbreeding coefficient) indicates the absence of inbreeding in the studied fish stock. Originality. The genetic structure of the Siberian sturgeon breeding group was studied for the first time during the domestication process during intensive cultivation in floating cages in the climatic conditions of the Forest-Steppe of Ukraine. Practical Value. The study results are aimed at improving breeding methods with sturgeons in aquaculture and improving the quality of brood sturgeon stocks. Keywords: Siberian sturgeon, genetic structure, heterozygosity, protein systems, polymorphism, domestication.

Некоторые особенности прилова осетровых видов рыб при осуществлении прибрежного промысла на кубанском побережье Азовского моря осенью 2023 – ранней весной 2024 г.

As a result of the collapse of the populations of Russian sturgeon and stellate sturgeon in the Sea of Azov in the late 1990s, their numbers were at an extremely low level. Since 2015, there has been a moderate trend towards an increase in the populations of Russian sturgeon and stellate sturgeon due to an increase in artificial reproduction and increased fish protection measures. Currently, an urgent task is to increase the reliability of estimating stocks of sturgeon populations by clarifying the parameters of populations and population processes both in the open sea and in the coastal zone. The aim of the study is to study the parameters and structure of by-catch of sturgeon fish in coastal fishing gear in the Sea of Azov. Data from trade journals on by-catch of sturgeon fish and the results of monitoring fishing on the Kuban coast of the Sea of Azov in autumn 2023 – early spring 2024 were used as materials for this work. The by-catch estimate for one cut of the sturgeon was performed: for Russian sturgeon – from 3.1 to 3.8 specimens./cuttings, dried apricots – from 0.3 to 2.1 specimens./a slice. In the autumn of 2023, the Russian sturgeon was found in 1.8 (in October) and 3.4 (in November) three times more often than the stellate sturgeon. In the spring of 2024, individuals of Russian sturgeon in the catches of stave seines were 12 times more common than stellate sturgeon. The average length (TL) of the by-catch of Russian sturgeon was 99.5 cm, and that of the grouse was 114.8 cm. In March 2024, the by-catch structure of Russian sturgeon and sturgeon was dominated by individuals aged 8-12 years. The presented materials make it possible to clarify the structure and parameters of sturgeon populations in autumn 2023 – spring 2024 and improve the accuracy of estimating their stocks.

Application of a cohort model of the population dynamics based on reservoir carrying capacity on the example of the russian sturgeon of the sea of Azov

The new approach to cohort modeling of fish populations in conditions of artificial reproduction, taking into account the possibilities of the reservoir’s food supply, was presented. The combined modeling approach includes the advantages of traditional cohort modeling of population dynamics and a hydrobiological approach to assessing the carrying capacity of a reservoir. The approbation of the presented approach was carried out by the Russian sturgeon Acipenser gueldenstaedtii population data in the Sea of Azov during the period 1985–2003. Results approbation of the presented model made it possible to reliably describe the dynamics of the commercial stock of the Russian sturgeon population in retrospective and has a significant advantage (R2 was 0,1 higher, the mean absolute error was lower on 6,2%) relative to the previously presented DAP model.

Growing results of arctic char juveniles (Salvelinus alpinus L., 1758) in a weakly saline artificial medium

The purpose of this work is to increase the rate of development and growth of Arctic char juveniles, a valuable promising specy for both commercial cultivation and artificial reproduction. The basis of the new method of the increasing cultivation biotech efficiency is the use the artificially saline biostimulating medium. For maximum stimulation of the juveniles growth rate, they were grown at a commercial farm in table salt solutions of 0.5–1.5‰ concentration, where 2 most important and widely used factors of the same effect were additionally included — optimal temperature and planting density, according to the basic principle of the natural impacts complexity. The maximum weight values (428±23 g) were obtained in a group with pre-sorted leaders of the lowest planting density (27 pd/m3) with that compared to more compacted (119±15 g) and control in fresh water (93.8±0.52 g) both in the same planting density (500 pd/m3). For the first time, an increase in the growth rate of Arctic char juveniles was observed when using even a slightly saline medium (0.5–1.5‰), below the threshold of critical salinity (4–8‰). The main advantage of growing juveniles in this combined medium — the growth rate increase to 26.97% was revealed, by comparative analysis. The industrial table salt solutions of low concentration are proposed to use in combination with known methods for optimizing the juveniles planting density (as well as temperature regimes, sorting) to accelerate the growth rate of juveniles that comparable to the effect of critical salinity in closed water supply systems of fish farms for yearround rearing.

The role of sodium bicarbonate in improving cold storage preservation of indigenous black rabbit spermatozoa

The population of indigenous black rabbits in Viet Nam has been steadily declining, primarily due to the increasing preference for commercial meat rabbit varieties. Consequently, the conservation and systematic breeding of indigenous black rabbits in the Mekong Delta are critical for preserving genetic diversity and sustaining local biodiversity. Sperm conservation is essential for the artificial reproduction of this species. This study aimed to find the optimal concentration of sodium bicarbonate (NaHCO3) buffer added to Tris Citrate Glucose (TCG) storage medium. Samples after collection were diluted with a storage medium containing sodium bicarbonate at concentrations of 0 mM, 15 mM, 25 mM and 35 mM, then refrigerated at 15ᵒC. The results showed that rabbit sperm achieved the best quality when supplemented with 25 mM NaHCO3 after 72 hours of storage. Specifically, the sperms had 59.25% overall motility, 22.34% progressive motility, 62.19% viability and 46.77% membrane integrity, the differences were statistically significant when compared with the remaining treatments (p<0.05). The study results indicate that supplementing the TCG preservation medium with 25 mM NaHCO3 significantly improves the quality of sperm during cold storage. This study has contributed to the development of the sperm conservation medium for indigenous black rabbits in the Mekong Delta.

Organization of additional research in the field of artificial reproduction of Pacific salmon at Sakhalin State University

Organization of additional research in the field of artificial reproduction of Pacific salmon at Sakhalin State University

The right to medical care and healthcare in the field of reproductive technologies: artificial intelligence and artificial reproduction

The article examines the peculiarities of the right to medical care and healthcare in the field of reproductive technologies, outlining the application of artificial intelligence in artificial reproduction. It is noted that the role of artificial intelligence in legal relations and the resolution of issues concerning civil legal capacity has increased with the use of such technologies for medical purposes. In the medical field, measures are being implemented to improve the quality and longevity of life for Ukrainian citizens, including: the creation of a national healthcare system using AI, based on the analysis of clinical, genetic, and behavioral data; the implementation of AI technologies in the development of advanced real-time medical diagnostic systems (virtual consultants, cybernetic experts, etc.); the expansion of medicine into a broader AI-controlled social sphere that utilizes all forms of health data, including genomics, metadata, electronic medical records, and biometrics, to ensure public health; the introduction of AI-based patient interaction tools (chatbots, mobile devices, etc.); educating patients on making informed decisions, self-monitoring health status, and disease prevention through AI; prioritizing (ranking) patient groups based on risk levels and conducting proactive interventions using AI technologies; and researching social determinants of health and managing public health using AI.It is emphasized that artificial reproduction, where AI takes on the role of the “mother,” is becoming an interesting legal issue for researchers. It is noted that artificial motherhood is not legalized in all countries, and the absence of an international act, particularly recommendations, may lead to conflicts in resolving cross-border family law disputes in the future. The article concludes that the use of AI in artificial reproductive methods is gradually becoming a practice in medical institutions. The application of this technology will facilitate effective fertilization and, in the future, embryo gestation. Additionally, an AI-powered incubator with innovative technologies is being developed and gradually implemented in medicine. However, many important issues remain unresolved, including the civil legal capacity and legal responsibility of artificial intelligence.

Revealing that artificial reproduction promotes increased genetic diversity between generations in Carpinus putoensis.

Carpinus putoensis, an endemic species of Putuo Island in the Zhoushan Archipelago, Zhejiang Province, China, is listed as critically endangered (D1) in the 1998 World List of Threatened Trees. Using 15 pairs of SSR primers markers, 143 individuals from three population generations were analyzed, generating 193 alleles. The average number of alleles (Na ) was 12.9, ranging from 4 to 28, while the average effective number of alleles (Ne ) was 4.900, with a range of 1.649 to 11.602. The multilocus outcrossing rate (tm ) was 1.000, and the single-locus outcrossing rate (ts ) was 0.871, ranging from 0.751 to 0.920 across the families studied. The difference between tm and ts (0.129) and the positive biparental inbreeding coefficients (0.080 to 0.249) indicate the presence of inbreeding. Moreover, an increase in Na and Ne was observed across generations, from 6.400 and 2.838 in the F1 generation to 9.200 and 4.228 in the F3 generation, respectively. These results highlight the need for artificial interventions to increase population size and improve genetic diversity, which are critical factors for the conservation and recovery of C. putoensis.

Rice Stubble Provides Overwintering Microhabitats for Spiders in Winter-Fallowed Rice Fields

Spiders are among the predominant predatory arthropods in rice field ecosystems. Although the potential of spiders for controlling pests during the growth stages of rice is well known, few studies have focused on the overwintering habits of spiders after rice harvesting. In the present study, we aimed to evaluate the potential of rice stubble as an overwintering microhabitat for spiders in winter-fallowed rice fields. To this end, we investigated the arthropod community composition and analyzed the prey spectra of common predators in rice stubble in winter-fallowed rice fields in Nanchong City, Sichuan Province, China. The results showed that abundant predatory arthropods, particularly spiders, were present in the rice stubble, followed by other arthropods and pests. Dietary analysis via DNA metabarcoding revealed the prey availability and/or predation frequency of spiders is low in winter rice fields. Nevertheless, pests and other arthropods (particularly collembolans) within rice stubble serve as food resources for predators, particularly spiders, in winter-fallowed rice fields. Our results confirm that rice stubble provides overwintering microhabitats for spiders in winter-fallowed fields. Therefore, it is particularly important to properly manage rice stubble in winter-fallowed rice fields to enhance the biological pest control services of predators (including spiders). In addition, our findings highlight the potential of rice stubble as a habitat for the artificial reproduction of spiders for pest control in rice fields.

Cryopreserved sperm does not affect larval ontogeny and quality in Rhamdia quelen.

Fish sperm cryopreservation is an important technique for optimizing juvenile production in aquaculture stations and laboratories and contributing to the conservation of endangered species. Despite its benefits, the cryopreservation process can cause cellular damage, affecting spermatozoa quality and offspring viability. This study aimed to evaluate the larval development of jundiá Rhamdia quelen originating from cryopreserved sperm. Larvae were obtained from artificial reproduction using oocyte samples from four females combined with fresh (Control) or cryopreserved/thawed sperm. The semen was diluted in the cryoprotective solution (1:3 ratio) consisting of skimmed milk powder (5%), methanol (10%), and fructose (5%), and was packaged into 0.25mL straws. The straws were then stored and cooled in liquid nitrogen vapor for 18h. The straws were individually warmed in a water bath at 25°C for 10s to thaw the samples. The experiments were performed in triplicates. Sperm quality, fertilization, hatching, and larval development were evaluated. After larval hatching, six larval collections were performed (5, 10, 15, 20, and 25days after hatching), and 15 larvae were sampled per collection per treatment. Cryopreservation reduced sperm motility (70.48 ± 7.70 fresh to 41.36 ± 4.80 cryopreserved semen), progressivity (3874 fresh to 2505 cryopreserved semen), and beat cross frequency (55.83 ± 155 fresh to 50.22 ± 190 cryopreserved semen). Increased the percentage of sperm with abnormal morphology and increased most sperm pathologies. Furthermore, the fertilization rate was lower in the cryopreserved group (63.1 ± 18, and 83.72 ± 7.59 for fresh semen), while hatching was not different between groups (65.3 ± 18.05 fresh, 48.89 ± 21.77 cryopreserved semen) Otherwise, the initial larval development morphology showed no difference in the appearance of structures such as the presence of the vitelline structure, pigmentation pattern, development of the anal pore, embryonic membrane, eye, barbells, notochord flexion, and fin rays, for both treatments. There was no significant difference in the frequency of structures between larvae from fresh and cryopreserved/thawed sperm, revealing a similar developmental pattern in both treatments. In conclusion, the cryopreservation protocol affects sperm quality; however, those sperm able to fertilize the oocytes originate normal larvae with regular larval development of R. quelen up to 25days old.

СОСТОЯНИЕ ПОПУЛЯЦИИ И ВОСПРОИЗВОДСТВА СТЕРЛЯДИ ACIPENSER RUTHENUS LINNAEUS, 1758 В БАССЕЙНЕ НИЖНЕГО ДОНА

Background. Before the construction of dams and hydrotechnical structures, sterlet was a commercially valuable species, widespread in the Don River Basin. Due to the river regulation and changes in the hydrological conditions influencing the natural spawning process, the sterlet population abundance in the Don River had decreased so much that this species was included in the Red Book of the Russian Federation, as well as regional Red Books. Relevance. The status of the sterlet population in the Don River remains insufficiently studied, despite the measures taken for its artificial reproduction and the constant increase in the number of released juveniles. The aimof this study is to analyze the status of the sterlet population in the Don River and to assess the effectiveness of the measures for its artificial reproduction in the modern period. Methods. The analysis of the current state of the sterlet population was based on the statistical data on the number of its juveniles released by hatcheries into the Don River, information on the number of the mature sterlet individuals transferred through the fish-lifting lock (FLL) of the Kochetovsky Hydrotechnical System, as well as the data collected during field research. Results. The effectiveness of the measures aimed at facilitation of the sterlet artificial reproduction in the Lower Don Basin has been assessed, and the necessity of expanding the research into the current state of the sterlet population to alter its conservation status has been indicated. Conclusion. The observed trend for the increase in the sterlet abundance in the Lower Don following the sizable releases of its juveniles by hatcheries in the last decade provides the basis for removal of this species from the Red Book of the Russian Federation and the Red Book of the Rostov Region.

ЭКОЛОГО-РЫБОХОЗЯЙСТВЕННЫЕ АСПЕКТЫ ФОРМИРОВАНИЯ СОВРЕМЕННОГО ГИДРОЛОГИЧЕСКОГО РЕЖИМА ВОДНЫХ ОБЪЕКТОВ АЗОВО-ДОНСКОГО РАЙОНА. ЧАСТЬ 2: ТРЕБОВАНИЯ РЫБНОГО ХОЗЯЙСТВА К ГЕОБОТАНИЧЕСКИМ УСЛОВИЯМ ПОЙМЫ НИЖНЕГО ДОНА; РЕЖИМ СОЛЕНОСТИ ТАГАНРОГСКОГО ЗАЛИВА; ЭФФЕКТИВНОСТЬ РАБОТЫ УСТЬ-МАНЫЧСКИХ РЫБОХОДНЫХ КАНАЛОВ

Background. The second part of the article examines the features of the floodplain landscapes of the Lower Don, evaluates the salinity regime and the formation of desalinated zones in Taganrog Bay in 2006-2023, and considers issues related to the operating efficiency of the Ust-Manych fish passage channels during the spring spawnings of 2017-2024. Relevance. The current understanding of the geobotanical features of the Don River floodplain and the transformation of its landscapes is incomplete, which contributes to the relevance of assessment of the quality of spawning grounds and their compliance with the fisheries requirements. Compilation of historic and current data provided the basis for geobotanical characterization of the floodplain area of the Azov-Don Fishery Region and made it possible to present new data on the habitat conditions of aquatic biological resources in Taganrog Bay, as well as on the efficiency of the Ust-Manych fish passage channels. The aim of this article was to investigate the compliance of the geobotanical conditions in the floodplain areas of the Azov- Don Region with the fisheries requirements, to determine the extent of the formation of desalinated zones in Taganrog Bay, and to evaluate the efficiency of the Ust-Manych fish passage channels in the spring season. Methods. The data collected over the course of the annual expeditionary (Taganrog Bay) and field (Ust-Manych channels) studies, the materials from AzNIIRKH archives, and the information from literary sources on the research topic have been used. When collecting, processing and analyzing samples and relevant data, the methods recommended in [1] have been used, including mathematical and statistical analysis, analytical graph plotting and mapping. Results. The fisheries requirements to the geobotanical conditions in floodplain spawning grounds have been formulated; based on the summarized modern and historical data, the features of the Don River floodplain landscapes have been studied, and an assessment of the compliance of the geobotanical conditions with the fisheries requirements has been given. The analysis of changes in water salinity and the formation of desalinated areas in Taganrog Bay for the period 2006-2023 has been carried out. The operating efficiency of the Ust-Manych fish passage channels has been estimated for the spring seasons of 1917-2024. Conclusion. The transformation of the Lower Don floodplain landscapes led to the non-compliance of its geobotanical characteristics with the fisheries requirements. The increase in salinity of the Taganrog Bay water observed in the period 2006-2023 (from 5.26 ‰ in 2006 to 11.78 ‰ in 2020) and the reduction in the area of desalinated zones in salinity gradations from 4 to 9 ‰ provide evidence of the deterioration of the habitat conditions both for juveniles and for mature individuals of the semi-anadromous commercial fish species of the Azov-Don Region, as well as serve as an indicator of reduction in the volume of the water bodies receiving the released juveniles obtained through the artificial reproduction. In 2017-2024, the Ust-Manych fish passage channels generally ensured the passage of semi-anadromous fish species to their spawning grounds, although during certain periods the flow velocities exceeded 1 m/s, reaching carrying speed.

Artificial insemination of bottlenose dolphins (Tursiops truncatus): a trial with simple instruments based on criteria for estrous behaviors linked to changes in estradiol levels and follicle development

Herein, we report a case of pregnancy of a female bottlenose dolphin (Tursiops truncatus) that was subjected to artificial insemination (AI) in water based on its estrous behavior using simple instruments. AI was performed on this female dolphin once or twice daily for 4 days at the detection of estrous behavior, such as floating horizontally and showing reduced responsiveness, likely indicating the appropriate timing for AI. The female was placed in supine a position in the water to position the genital slit above the water surface. A Nélaton catheter (Fr. 10, 40 cm length), with its tip modified, was inserted approximately 20 cm into the vagina through the genital slit, and 1-2 ml of fresh semen was injected. The AI procedure was performed within 1 min by two technicians. Thus, this AI method may be a new choice for artificial reproduction, as pregnancy success can be achieved with relatively less cost, less difficulty, and less invasive treatments of cetaceans.

Estimating the occurrence of chum salmon Oncorhynchus keta of artificial origin on spawning grounds in the rivers and lakes of Iturup Island

Artificial reproduction of pacific salmon has been repeatedly criticized due to negative impact on natural populations. One of its aspects is replacement of wild spawners by spawners originated from hatchery on natural spawning grounds. This problem is relevant to Iturup Island, where the chum salmon stock is formed by both natural reproduction and artificial breeding. To evaluate their ratio, otolith marking of juveniles has been massively implemented at Iturup salmon hatcheries since 2009. The otoliths of chum salmon were collected for analysis from the spawning grounds in 6 rivers and lake-river systems of the Okhotsk Sea coast in the northern part of Iturup Island and at the slaughter point of salmon hatcheries from 2012 to 2022. Microstructure of otoliths from 8229 fish individuals, including 2709 specimens of сhum salmon, was examined to identify the tagged fish. The chum salmon of artificial origin were presented on all examined spawning grounds. Their number was calculated taking into account the percentage of tagged juveniles released from the hatcheries. Low level of straying was concluded for chum salmon on Iturup Island. Long-term dynamics of the ratio between wild and artificial spawners on spawning grounds was determined by changes in volume of juveniles release. Until 2014, the Reidovy and Kurilsky hatcheries released 50.106 chum juveniles annually, and the spawners of artificial origin were found sporadically on the spawning grounds in “wild” rivers. New fish hatcheries constructed after 2010 provided increase of their portion in 2014–2022 to 9.6–13.6 % on the spawning grounds unaffected to artificial reproduction and up to 93.3 % on the spawning grounds in the rivers with hatcheries. These high returns were supported by release of 74.4–191.8.106 juvenile fish annually. In the Reidovaya and Kurilka Rivers with a branched network of tributaries, the highest occurrence of artificial spawners was observed on the spawning grounds neighbored with hatcheries, whereas their portion decreased to 20 % on the spawning grounds in large tributaries of lower reaches; possibly, spawning grounds where the spawners of artificial origin are absent still exist in the basins of these rivers. Some increase of straying should be probably expected in future years because of huge amount of juvenile chum salmon released into the rivers of Prostor and Kurilsky Bays after 2020, at least 175.106 ind.

Лінійний темп росту вирезуба (Rutilus frisii Nordman, 1840) у басейні річки Дністер

Purpose. To achieve high rates of recruitment of natural localities with vyrezub (Rutilus frisii Nordmann, 1840), it is a priority to increase the size characteristics of fish seeds under aquaculture conditions, which is interdependent on the linear growth rate of different age groups of vyrezub. The results of the study on size characteristics of this species will form the basis of the future technology for its artificial reproduction in Ukraine. Methodology. The incomplete biological analysis was carried out directly at the sampling site, measurements were carried out according to the generally accepted method without removing fish from the water. After measurements, all juveniles were released into their natural habitat alive and unharmed. The age of the fish and scale measurements were determined using an MBS-10 binocular microscope. Based on the results of the measurements, the linear growth of vyrezub by age category was back calculated according to the Lea’s method. The growth rate was assessed using the analysis of growth in absolute and relative values, the specific growth rate of different age groups of the vyrezub. Findings. Results of determining the age structure of the vyrezub population of the Dnister River showed that in the first year of life it is characterized by a length of 55 mm to 120 mm. The results of back calculation of the growth of the vyrezub showed that in the second year of life, most fish have a length of 156 mm, in the third – 273 mm, and in the fourth – about 391 mm. In the future, the linear growth of fish slows down somewhat, which is explained by the period of sexual maturation and the first spawning. In the fifth year of life, the average individual length of the vyrezub was about 445 mm, in the sixth year - 488 mm, in the seventh year of life - 575 mm. At the age-8+, the average individual length of fish body was 640 mm. The results of the reconstruction of growth rate showed that the fastest linear growth rate was observed in the first two years of life. The dynamics of rapid growth was due to the presence of favorable feeding areas for fish juveniles, which allowed them to escape the trophic pressure of predators. In the fourth and fifth years of life, there was a decrease in the linear growth rate, which was explained by the sexual maturation of males and females, as well as the period of the first spawning. Originality. For the first time, the linear structure of vyrezub of the Dnister River and the rivers of its basin within the Ivano-Frankivsk region has been analyzed. The average growth parameters were determined and analyzed, and the linear growth rate of different age groups of the vyrezub was reconstructed. Practical Value. The study results will be the basis for implementing methodological aspects of artificial reproduction of vyrezub to solve the problem of preserving the species diversity of fish species valuable in terms of environmental protection. Keywords: vyrezub (Rutilus frisii Nordmann, 1840), sclerites, linear growth, different age groups, length, Dnister River.

Chromosome-level genome assembly of the ratmouth barbel, Ptychidio jordani

The ratmouth barbel (Ptychidio jordani) is a critically endangered freshwater fish from the Cyprinidae family, primarily due to overfishing and habitat disruption. To address the challenges of its shrinking wild populations and the difficulties in artificial reproduction, we sequenced, assembled, and annotated a high-quality chromosome-level genome of P. jordani using next-generation short-read sequencing, third-generation long-read sequencing, and Hi-C sequencing. The final genome assembly was 1.14 Gb, consisting of 25 chromosomes with a contig N50 of 25.14 Mb and a scaffold N50 of 42.91 Mb. We identified 25,183 protein-coding genes, 751.75 Mb of repeats, and 19,373 ncRNAs. Methylation loci on most chromosomes ranged from 1,000 to 3,000 per 100 kb window. Gene expression levels across various tissues were analyzed, revealing 12,135 (caudal fin), 11,465 (liver), 14,438 (gill), 12,413 (heart), 8,301 (spleen), and 3,578 (kidney) differentially expressed genes compared to muscle. The comprehensive genomic and transcriptomic resources generated here will aid in understanding the ecology, adaptation, and environmental responses of P. jordani, supporting future research and conservation efforts.

The Influence of Sperm Activation Methods and Oocyte Collection on the Reproductive Effects of Northern Pike (Esox lucius)

This study compared the quality of northern pike eggs collected using traditional methods (hand stripping) and pneumatic methods (air stripping). The effects of different activation solutions (0.4% NaCl, 0.8% NaCl, and hatchery water) on egg fertilization under controlled conditions were also investigated. After egg collection, the Pseudo-Gonado-Somatic Index (PGSI) was measured; the PGSI values in the samples obtained using the pneumatic method (13.8 ± 3.9%) were lower, but did not differ statistically from those obtained by hand stripping (16.5 ± 5.4%). The 0.4% NaCl solution proved to be the most effective for sperm activation, as assessed by the Computer-Assisted Sperm Analysis (CASA) system, compared to the 0.8% NaCl solution. The pneumatic method achieved a higher egg collection efficiency (93.7% occlusion) than the traditional method, with significant differences observed in groups activated with water. The average hatching percentage of larvae was 89.5% in groups using the pneumatic method, compared to 71.2% in the traditional groups, highlighting the advantages of this modern approach. The application of the pneumatic method and 0.4% NaCl for the artificial fertilization of northern pike resulted in higher fertilization and hatching rates compared to other techniques, making this method a promising option for the artificial reproduction of other fish species.