Fish Reproduction Research Articles

Hormonal dynamics of matrotrophy vs. lecithotrophy in live-bearing fish reproduction

We explored the relationship between gestational states, fecundity, and steroid hormone levels in three species of live-bearing fish with different maternal provisioning strategies. We studied two lecithotrophic species, Gambusia affinis and Xiphophorus couchianus, where embryos feed exclusively on yolk stored in the eggs, and one matrotrophic species, Heterandria formosa, which actively transfers nutrients to embryos through a follicular placenta. We measured water-borne cortisol, estradiol, and progesterone along with brood size (fecundity) and gestational stage(s). We examined the physiological costs of both maternal provisioning modes. Matrotrophy likely imposes energetic demands due to active nutrient transfer, while lecithotrophy may incur costs from carrying many large embryos. We hypothesized that fecundity, gestational stage, and hormones would covary differently in lecithotrophic vs. matrotrophic species. We found no relationships between hormones and fecundity or gestational stage in any species. However, in H. formosa, we found a positive relationship between estradiol levels and female mass, and a negative relationship between progesterone levels and female mass indicating a change in the circulating levels of both hormones as females grow. We observed differences in average hormone levels among species: the matrotrophic species had higher progesterone and lower estradiol compared to lecithotrophic species. Higher estradiol in lecithotrophic species may relate to egg yolk formation, while placental structures could play a role in progesterone production in matrotrophic species. Elevated cortisol in H. formosa suggests either higher energetic costs or a preparative role for reproduction. Our findings highlight progesterone's importance in maintaining gestation in matrotrophic species, like other placental species.

The Potentials of Phytoestrogen Compounds in Aquaculture – A Review

Abstract All organisms require the ability to engage in either sexual or asexual reproduction in order to ensure their own survival. In aquaculture, when one sex outgrows the other faster, farmers use hormones to stimulate growth. Furthermore, the production of fish based on sexual dimorphism is predominantly executed through the utilization of estrogens and androgens. Environmentally, these compounds may pollute the ecosystem and cause endocrine system alterations that cause harmful effects; thus, they must be handled carefully to assure environmental, biological, and food safety. Phytoestrogens as natural non-steroidal phenolic plant chemicals that resemble 17-β-estradiol, could be employed as a safe alternative source of natural estrogens. The phytoestrogens have many biological effects due to their ability to compete with estrogen receptors, but they may negatively affect fish production, reproduction, and behaviors under controlled conditions. Thus, the current literature emphasizes on the beneficial effects of phytoestrogens on aquatic animal performance, behaviors, and some reproductive features.

Reversible Sterilization of Channel Catfish via Overexpression of Glutamic Acid Decarboxylase Gene.

The confinement of transgenic fish is essential to prevent their escape and reproduction in natural ecosystems. Reversible transgenic sterilization is a promising approach to control the reproduction of transgenic fish. Therefore, the present study was conducted to develop a reversibly sterile channel catfish (Ictalurus punctatus) via the transgenic overexpression of the goldfish (Carassius auratus) glutamic acid decarboxylase (GAD) gene driven by the common carp (Cyprinus carpio) β-actin promoter to disrupt normal gamma-aminobutyric acid (GABA) regulation. Three generations of GAD-transgenic fish were produced. All studied generations showed repressed reproductive performance; however, this was not always statistically significant. In F1, 5.4% of the transgenic fish showed a sexual maturity score ≥ 4 (maximum = 5) at five years of age, which was lower (p = 0.07) than that of the control group (16.8%). In the spawning experiments conducted on F1 transgenic fish at six and nine years of age, 45.5% and 20.0% of fish spawned naturally, representing lower values (p = 0.09 and 0.12, respectively) than the percentages in the sibling control fish of the same age (83.3% and 66.7%, respectively). Four of six pairs of the putative infertile six-year-old fish spawned successfully after luteinizing hormone-releasing hormone analog (LHRHa) therapy. Similar outcomes were noted in the three-year-old F2 fish, with a lower spawning percentage in transgenic fish (20.0%) than in the control (66.7%). In one-year-old F2-generation transgenic fish, the observed mean serum gonadotropin-releasing hormone (GnRH) levels were 9.23 ± 2.49 and 8.14 ± 2.21 ng/mL for the females and males, respectively. In the control fish, the mean levels of GnRH were 11.04 ± 4.06 and 9.03 ± 2.36 ng/mL for the females and males, respectively, which did not differ significantly from the control (p = 0.15 and 0.27 for females and males, respectively). There was no significant difference in the estradiol levels of the female transgenic and non-transgenic fish in the one- and four-year-old F2-generation fish. The four-year-old F2-generation male transgenic fish exhibited significantly (p < 0.05) lower levels of GnRH and testosterone than the control fish. In conclusion, while overexpressing GAD repressed the reproductive abilities of channel catfish, it did not completely sterilize transgenic fish. The sterilization rate might be improved through selection in future generations.

A complete study of neuroendocrine regulation of fish reproduction. 4. Migration impulse as a starting mechanism of spawning

The participation of the hypothalamo-hypophysial neurosecretory system (NS) in the initiation of anadromous fish spawning migration was established on the basis of ecological-histophysiological analysis the results of histomorphological, immunohistochemical and electron microscopic studies for the first time. Activation of the neurosecretory products synthesis in the neurosecretory cells perikaryons and their excretion into the cerebrospinal fluid of the III brain ventricle in anadromous migrants forms at the beginning of the river spawning migration, spring-spawning: Russian sturgeon, stellate sturgeon and autumn-spawning: pink salmon and chum salmon, was shown. Transport and mass accumulation of neurosecretory products in the neurohypophysis were discovered at the same time. It is concluded, that the NS impacts a complex synchronous effect, which consists: firstly, in the neurotropic effect of nonapeptide neurohormones (NPh) on behavioral centers, which causes a dominant state of CNS excitation corresponding to the “Migration impulse”; secondly, in the violation of the long-term adapted marine “Pastured” level of osmoregulation; and thirdly, in the cessation of the well-known antigonadotropic effect of NPh, which contributes the organism transition to the energyconsuming energy type of metabolism. A comparative analysis (cross-analysis) of our own and literature data confirms the commonality and points to the universality of this metabolic mechanism for different forms of migration in fish ontogeny, which allows us to consider it as the most important aromorphosis type of phylogenetic adaptations, aimed at the species biological progress achieving. In the subsequent navigational mechanisms of homing, widely covered in the world literature, the leading role is played by the luliberinergic centers of the hypothalamus. The ecological diversity of these population-level mechanisms and the presence of straing in fish allow us to consider them as specializations of microevolutionary origin. The most promising direction for the further neuroendocrinological research development seems to be the analysis of the mechanisms of imprinting in connection with the enhancement of growth and survival of juveniles in the critical salinity medium, and for the purpose of homing control (development of the commercial fish-return biotechnology management) — the mechanisms of interaction between the NS and the luliberinergic centers in the neuroendocrine complex of CNS.

Environmentally relevant estrogens impaired spermatogenesis and sexual behaviors in male and female zebrafish

Environmental estrogens (EEs) are found extensively in natural waters and negatively affect fish reproduction. Research on the reproductive toxicity of EEs mixtures in fish at environmentally relevant concentrations is scarce. In this study, adult male zebrafish were exposed for 60 days to EES (a mixture of EEs), EE2-low (5.55 ng/L, with an estrogenic potency equal to EES), and EE2-high (11.1 ng/L). After exposure, the expression levels of vtg1, vtg3, and esr1 in the livers in EES-treated fish remained unaltered, whereas they were significantly increased in EE2-treated fish. Both EE2-high and EES exposures notably reduced the gonad somatic index and sperm count. A disrupted spermatogenesis was also observed in the testes of EE2-high- and EES-exposed fish, along with an alteration in the expression of genes associated with spermatogonial proliferation (pcna, nanog), cell cycle transition (cyclinb1, cyclind1), and meiosis (aldh1a2, cyp26a1, sycp3). Both EE2 and EES significantly lowered plasma 11-ketotestosterone levels in males, likely by inhibiting the expression level of genes for its synthesis (scc, cyp17a1 and cyp11b2), and increased 17β-estradiol (E2) levels, possibly through upregulating the expression of cyp19a1a. A significant increase in tnfrsf1a expression and the tnfrsf1a/tnfrsf1b ratio in EE2-high and EES-treated males also suggests increased apoptosis via the extrinsic pathway. Further investigation showed that both EE2-high and EES diminished the sexual behavior of male fish, accompanied with reduced E2 levels in the brain and the expression of genes in the kisspeptin/gonadotropin-releasing hormone system. Interestingly, the sexual behavior of unexposed females paired with treated males was also reduced, indicating a synergistic effect. This study suggests that EES have a more severe impact on reproduction than EE2-low, and EEs could interfere not only with spermatogenesis in fish, but also with the sexual behaviors of both exposed males and their female partners, thereby leading to a more significant disruption in fish reproduction.

The state of spawning grounds, a study of the biology and population dynamics of pacific salmon on Kunashir Island (Southern Kuril Islands) in 2023

The purpose: formation of scientific foundations for improving the efficiency of salmon management on Kunashir Island (South Kuril zone) to ensure the sustainable exploitation of the commercial stock of Pacific salmon, maintain the necessary level of their reproduction, preserve the habitat, as well as improve scientific approaches to forecasting commercial catches.Methods used: the work was carried out in accordance with the methods generally accepted in fisheries research.Result: information was obtained on the dynamics of Pacific salmon entry, the filling of spawning grounds and the state of reservoirs on Kunashir Island. The collection of materials characterizing the biological indicators of chum salmon producers was carried out. Statistical information was obtained on catches of chum salmon and artificial reproduction of salmon fish on Kunashir Island.Practical significance: information on the filling of the spawning grounds of Pacific salmon on Kunashir Island and the quality indicators of their producers will be used to substantiate fishing regulation measures. Data on the state of artificial and natural reproduction of Pacific salmon are intended to develop a strategy for the development of artificial reproduction on Kunashir Island.

Gametogenesis and seminatural reproduction of the Amazon twospot astyanax Astyanax bimaculatus (Linnaeus, 1758) cultivated in an enriched environment

Environmental enrichment is used to provide well-being to the animals, such as fish, in captive conditions, mimicking their natural habitat. It may influence fish behavior, physiology, and survival. In terms of reproduction, however, the relationship between environment enrichment and successful reproduction in captivity is still poorly explored in fish species. Aiming to understand any possible benefits of structural enrichment on fish reproduction, 10-days-hatched larvae of the twospot astyanax Astyanax bimaculatus were raised for 18 weeks in tanks with different elements of structural environmental enrichment (PVC pipes, stones, and artificial plants). In the 5th month of life, those animals were hormonally induced to reproduce to assess gamete formation and offspring quality. Animals raised in a sterile-reared environment (non-enriched) showed earlier spawning than the enriched one, presenting significant quantities of Postovulatory follicle complexes (POCs) and cells in atresia in female ovaries, indicating possible reproductive dysfunction or stress, as well as a greater quantity of empty testicular lumen in males, indicating great release of sperm. On the contrary, animals cultivated in enriched environments showed gonads filled with semen in males and vitellogenic oocytes in females. Furthermore, offspring from the sterile-reared group presented significant rates of larval abnormality compared to the enriched group. In conclusion, the results of this study show that environmental enrichment can interfere with the reproduction of fish in captivity, mainly by preventing early maturation of gametes, which can result in low-quality offspring and, consequently, low production of fish species.

Novel insights into immune stress markers associated with myxosporeans gill infection in Nile tilapia (molecular and immunohistochemical studies).

Nile tilapia (Oreochromis niloticus) is valued in aquaculture because of its quick development and ability to thrive in various environments. Myxosporeans are among the fish parasites that affect fish productivity, as they impact fish growth and reproduction, resulting in large fish deaths in farms and hatcheries. This study has been focused on morpho-molecular identification for the myxosporean parasites infecting Nile tilapia from three governorates in Egypt and assessment of gene expression of different cytokines (Interleukin-1βeta (IL-1β), major histocompatibility complex class II (MHC-II), and clusters of differentiation 4 (CD-4) and 8 (CD-8)) in tissues. Additionally, this work aimed to correlate the developed histopathological alterations and inflammatory reactions in gills with immunohistochemical expression of inducible nitric oxide synthase (iNOS) and tumor necrosis factor-alpha (TNF-α). Finally, the infected fish's cortisol levels and blood glucose were assessed. Results of BLAST sequence analysis of the 18S rRNA for the collected protozoans confirmed Myxobolus agolus, M. brachysporus, M. tilapiae, and Henneguya species. The molecular characterization of the immunological status of gills revealed marked upregulation of different inflammatory cytokines in the gills of infected fish. There was a significantly increased serum cortisol and glucose level in infected fish compared with control, non-infected ones. Severe histopathological alterations were observed in the infected fish gills, associated with increased expression of iNOS and TNF-α and related to myxosporean infection. The present study provides new insights into oxidative stress biomarkers in Nile tilapia infected with Myxosporeans and elucidates the gill's immune status changes as a portal of entry for protozoa that contribute to tissue damage.

Reproductive Cycle, Size at Maturity and Fecundity of Giuris margaritaceus in Limboto Lake

Graphical Abstract Highlight Research The size of the first mature gonads in hulu'u fish can be analyzed. Differences in sperm and egg size characterize sexual maturity. Sexual maturity is not influenced by season. Hulu'u fish have an asynchronous spawning type. Abstrack Understanding fish reproduction biology, particularly sexual maturity, the reproductive cycle, and fecundity, is useful for managing fisheries. The reproduction of Giuris margaritaceus in Limboto Lake is regrettably unknown. Over a year, fish specimens (N = 662) were gathered. They ranged in length from 6.5 to 20.9 cm (mean SD 10.9±2.5). Fecundity varied from 30,057 to 61,920. The first sexual maturity of male and female fish occurred at different sizes, 11.2 cm and 10.3 cm, respectively. This information is needed to determine this fish's lowest acceptable harvest length under the management aim to enter all-female fish for reproduction at least once. We estimated the reproductive of G. margaritaceus cycle using the size of the oocytes, histological analysis of the ovaries, and monthly mean GSI. These techniques produced the same reliable conclusion: G. margaritaceus can spawn yearly, with maximal between September and October. Based on this finding, spawners of Giuris margaritaceus can be kept from entering the reproductive stock between September and October. Future efforts to fine-tune fishing efforts for the effective management of G. margaritaceus may be aided by the study's findings.

Water Level Fluctuation Effect on Fish Reproduction Success

Alteration of water levels of the lake/reservoir due to changes in river discharges, upstream abstraction, and drawdown regulation due to hydropower generation has been reported as among the major challenges to fish physiology and ultimately reproduction. Variations in lake/reservoir water levels influence biodiversity and the abundance of lake/reservoir biota. Variations have the greatest impacts in the littoral zones hence, interfering with fish spawning, incubation, and hatching of eggs, as well as the development of larvae, postlarvae, and juveniles. This particular paper reviews the literature available on the effect of the reservoirs/lakes’ water level fluctuations on fish reproduction success using the documentary view method. The literature argues that water level fluctuations have both positive and negative impacts depending on frequency, magnitude, and duration and the species exposed. Extreme fluctuations tend to bring more adverse impacts. It further indicates that extreme and untimely water level fluctuation has direct impacts on the aquatic habitats and ultimately impacts fish assemblage and their populations. Few articles indicate the range of decrease or increase of water level, duration of such events, and effects they have on reservoir/lake ecosystem functions and fish physiology. Nevertheless, quantification of moderate and extreme water level fluctuation and associated effects is lacking. Although water level fluctuation is an important environmental cue for aquatic organisms, literature shows that the reduction of extreme water level variations especially multiannual variations is vital for fish reproduction. Therefore, upstream water use and reservoir operations should take into consideration the effects of water level fluctuations on reservoir structure, biological functions, and ultimate effects on fish reproduction.

Pengaruh Penambahan Ampas Tahu Dan Keong Mas (&lt;i&gt;Pomacea canaliculata&lt;/i&gt;) Pada Ratro Pellet Komersil Terhadap Pertumbuhan Ikan Lele (C&lt;i&gt;larias gariepinus&lt;/i&gt;)

The need for fish food is one of the essentials that can determine the level of success of the fish growth and development process. This research aims to analyze the effect of a combination of pelleted feed and animal feed on the growth and survival of catfish (Clarias gariepinus). The research was carried out for 60 days, at the Mataram University fish production and reproduction laboratory using an experimental method with a completely randomized design (CRD) consisting of 5 treatments and 3 replications, namely: A: 100% commercial feed (control), B: Fish Pellets 50% + Golden Snail 25% + Tofu Dregs 25%, C: Fish Pellets 25% + Golden Snails 50% + Tofu Dregs 25, D: Fish Pellets 25% + Golden Snails 25% + Tofu Dregs 50% and E: Fish Pellets 34% + Keong Mas 33% + Tofu dregs 33%. Test parameters include absolute weight, absolute length, specific weight growth rate, specific length growth rate, feed conversion ratio, feed utilization efficiency and survival and water quality. Data were analyzed using Analysis of Variance (ANOVA) and continued with the Duncan test. The results of this study showed that the best growth and survival of catfish was found in the treatment with 34% commercial feed, 33% golden snails and 33% tofu dregs (P4) with an absolute weight of 15.09 g, an absolute length of 7.05 cm , the specific weight growth rate was 3.86%/day, the length growth rate was 1.3%/day, the feed conversion ratio was 1.18, the feed efficiency rate was 85.91% and the survival rate was 73.33%. The proximate test results showed that the highest content was found in the treatment given 25% commercial feed, 50% golden snails and 25% tofu dregs (P2) with a dry content of 36.39%, crude fiber 10.86% and crude protein 31.48%.

Pengaruh Pemberian Cacing Darah (Chironomus sp.) Kering Terhadap Kecerahan Warna Ikan Guppy (Peocilia reticulata)

This research aims to analyze the effect of adding natural blood worms (Chironomus sp) to the feed on the color of guppy fish (P. reticulate). The research was carried out for 50 days, at the Fish Production and Reproduction Laboratory, Mataram University using experimental methods with a completely randomized design (RAL ) consisting of 4 treatments and 3 repetitions, namely: A: Control feed (100%) B: 75% control feed and 25% dried blood worms C: 50% control feed and 50% dried blood worms and D: Control feed 25% and 75% dried blood worms. Test parameters include carotenoid content, brightness of fish color, absolute weight, specific growth rate, survival and water quality. Data were analyzed using Analysis of Variance (ANOVA) and continued with the Duncan test. The results of the research show that dried blood worms have the potential to be a source of natural carotenoids in increasing color brightness and do not have a negative impact on the growth and survival of guppy fish. The addition of up to 50% dried blood worms to the formulated feed was able to increase the color brightness of guppy fish with a Lightness (L*) value of 56.95, Redness (a*) of -0.09, Yellowness (b*) of 14.84 , Hue is 258.01 and Chroma value is 110.12

The regulation of prolactin secretion and its targeting function of teleost

Prolactin is involved in regulating various physiological activities of vertebrates and is one of the most momentous pituitary hormones. However, not enough attention is currently paid to prolactin, especially in teleost. This paper aims to gather, organize, and analyze recent studies on the regulation and functions of prolactin. By comparing with other animal groups, it highlights the significant role of prolactin in fish reproduction, immunity, growth, and osmotic pressure regulation, as well as the upstream and downstream factors that may be involved in the regulation of prolactin functions were introduced to provide a theoretical basis for the in-depth study and potential practical application of prolactin.

Comprehensive analysis of histophysiology, transcriptome and metabolome tolerance mechanisms in black porgy (Acanthopagrus schlegelii) under low temperature stress

Low temperature stress has adverse effects on fish growth and reproduction, causing huge economic losses to the aquaculture industry. Especially, black porgy (Acanthopagrus schlegelii) farming industry in north of Yangtze River has been severely affected by low temperature for a long time. To explore the tolerance mechanism of black porgy to low temperature stress, the experiment was designed. The liver and gill tissues of black porgy were taken from the water temperature point of 15 °C (control group named as CG), 3.8 °C (cold sensitive group named as CS) and 2.8 °C (cold tolerant group named as CT) with a cooling rate of 3 °C/d from 15 °C for histophysiology, transcriptomics and metabolomics analysis. After cold stress, the histological results showed that the nucleus of the black porgy liver tissue appeared swelling, the cell arrangement was disordered; meanwhile the gill lamellae were twisted and broken, the epidermis was detached and aneurysm appeared. In addition, the expression of antioxidant, glucose metabolism and immune-related enzymes in the liver and gill of black porgy also changed significantly after low temperature stress. By analyzing the transcriptome and metabolome dates of black porgy liver, 3474 differentially expressed genes (DEGs) and 689 differentially expressed metabolites (DEMs) involved in low temperature stress were identified, respectively. The results of the transcriptome and metabolome combined analysis showed that individuals in the CS group mainly supplied energy to the body through lipid metabolism and amino acid metabolism, and meanwhile the apoptosis pathway was activated. While, individuals in the CT group mainly through glucose metabolism and steroid hormone biosynthesis to supply energy for the body. The validation results of qPCR on eight functional genes further demonstrated the reliability of RNA-Seq data. In summary, the results provide molecular information about adaptation to climate change and genetic selection of black porgy.

Характеристика структурных изменений ихтиофауны в северной части Аграханского залива за последние 5 лет

The northern part of the Agrakhan Gulf, which is a part of the Tersko-Caspian fishery complex of Dagestan, plays an important role in the formation of stocks of commercial fish species, having abundant spawning, nursery and wintering grounds. The efficiency of natural reproduction of fish is determined by the state of the hydrological and hydrochemical regime in the reservoir, which in recent years in this reservoir can be characterised as unfavourable. Studies carried out in North Agrakhan in the period from 2018 to 2022 have shown negative changes in the structure of ichthyofauna, manifested in a decrease in the number of juveniles of passable, semipassable, freshwater fish species and an increase in tuvodny fish of the lake-river complex. The number of juveniles of passable fish species has decreased almost twofold, kutum stocks have reached a critical level, the prevailing semi-passable fish species, which account for up to half of the total volume of recorded juveniles, are also decreasing, although to a lesser extent. Freshwater fish species are in a depressed state, the number of juvenile fish is decreasing from year to year, and has decreased more than twofold over the 5 years under study. The total number of segolets of low-value fishery lake-river fish species for 5 years increased 2 times and was 37% of the total volume of all fish species. In general, in the northern part of the bay the dominance of fish species in the northern part of the bay has become dominant among passable fish species - redfish, semipassable fish species - bream, freshwater fish species - redfish, lake-river fish species - redfish and crucian carp. Such species as kutum, pikeperch and practically all freshwater species are at the stage of extinction, mainly tench, which was recorded in catches only once.

Аналіз стану умов відтворення аборигенних іхтіопопуляцій Стир-Горинського гідроекологічного коридору на території Західного Полісся України

Purpose. To investigate the state of reproduction conditions, current and in dynamics since 1922, for native ichthyopopulations (NI) of the Styr-Horyn Hydroecological Corridor (HEC) on the territory of the Western Polissiya of Ukraine. Methodology. The Styr-Horyn HEC was studied according to the following parameters: hydrological regime and duration of water stay on the floodplain; state of the basin surface; speed of channel flow; amount of water exchange; quality of aquatic environment; natural-temporal changes of the channel, floodplains, tributary network; number of ecotones; qualitative and quantitative characteristics of fish juveniles. The hydrological regime was studied using the analysis of runoff hydrographs located in the Volyn, Rivne, and Zhytomyr regions starting from 1922. To assess water quality, KND No. 211.1.4.010-94, “Methodology of ecological assessment of surface water quality by relevant categories”, SOU – 05.01.37-385: 2006, was used. Ichthyological studies were carried out in the field and laboratory according to standard methods with the use of identification keys primarily using the data of test catches and the classification of V. G. Nikolskyi. Statistical and mathematical analysis was performed using the Delfi programming language, relevant computer programs (Mathcad, Excel, Xara) and formulas, including authors’ ones. Findings. An analysis of the Styr-Horyn HEC was carried out on the basis of restorative ichthyoecology using the basin principle and riskology approaches. The hydroecological and ichthyoecological factors affecting the reproduction of NI were studied. The natural fish reproduction localities (NFRL) in this region have been identified. Originality. For the first time, a comprehensive analysis of the state of the reproduction conditions of the Styr-Horyn HEC on the territory of the Western Polissiya of Ukraine was carried out starting from 1922. In addition, a prognostic assessment of the NFRL of this HEC on the territory of Ukraine has been provided. Practical value. The conducted studies are already successfully used in the work of higher educational institutions of Ukraine in the field of training “Aquatic bioresources and aquaculture”.In addition, they are used by fish protection authorities in several regions of Ukraine, in particular for certification of wintering grounds. In the future, their implementation is planned at the level of the national environmental protection policy and in the preparation of regulatory documents regarding the determination of the damage caused and the extent of the damage. Keywords: Pripyat River, Horyn River, Styr River, hydroecology, ichthyoecology, Western Polissiya, hydroecological corridor, natural fish reproduction localities, spawning grounds, wintering grounds, fish migrations, native ichthyofauna.

Optimizing reservoir operation incorporating ecological demand and stability requirement

AbstractThe construction and operation of large‐scale reservoirs alter the natural river flow regimes and destroy the original suitable reproduction and living conditions of aquatic organisms. Especially during the spawning season, the fluctuating water flow process is particularly important for fish reproduction. A bi‐objective optimization model considering both the environmental flow demand for fish spawning and the stability of hydropower output is established in this study and solved by one of the most widely used algorithms for multi‐objective problems, the Non‐Dominated Sorted Genetic Algorithm‐II. The derived Pareto Front can be used to guide reservoir operation during fish spawning seasons. The model proposed in this paper is applied to the Yangqu Reservoir, currently under construction on the upper Yellow River in China. The results show that the stability of hydropower output can still be improved by 4.80% to 10.56%, even if the environmental flow demand is taken into account. Even for the scheme preferring ecological recovery, the stability of hydropower output can be increased by more than 0.85%.

Status of the reproductive system of anchovy sprat (Clupeonella engrauliformis, Borodin, 1904) in the Caspian sea

The impact of negative factors on the population of anchovy sprat (Clupeonella engrauliformis, Borodin, 1904) continues, and therefore in recent years there has been a steady downward trend in the abundance and density of the species. Research catches of anchovy sprat are declining. One of the conditions contributing to the population recovery is an optimal, without critical pathologies condition of reproductive system of individuals. The purpose of this work is to study the condition of testes and ovaries of anchovy sprat. According to the histological picture of germ cells it is possible to objectively assess the state of reproductive ability of individuals. The study was carried out using the methods of classical histology. The material was gonads of females and males sampled in the summer of 2023 in the Middle Caspian Sea. According to the results of histological study it was found that gonads have different stages of maturity (II–III, III, IV and V). The presence of direct correlations between maturity indices (gonad weight, gonadosomatic index, maturity coefficient) in individuals of both sexes was found. In females, the size of oocytes of different stages of maturity is described, and the absence of correlation between cell diameter and length and mass of the individual is revealed. Distinctive features of resorption of oocytes of III and IV stages of maturity by such characteristics as shape, color and transparency of the cell are given. The proportion of females with resorbed oocytes (67%) and the average proportion of cells with developmental abnormalities (24%) were noted. The results of this study may contribute to a better understanding of the processes occurring in the reproductive glands of male and female anchovy sprat, which is very important for fish reproduction.

Triphenyltin induced darker body coloration by disrupting melanocortin system and pteridine metabolic pathway in a reef fish, Amphiprion ocellaris

Triphenyltin (TPT) is a typical persistent organic pollutant whose occurrence in coral reef ecosystems may threaten the survival of reef fishes. In this study, a brightly colored representative reef fish, Amphiprion ocellaris was used to explore the effects of TPT at environmental levels (1, 10, and 100 ng/L) on skin pigment synthesis. After the fish were exposed to TPT for 60 days, the skin became darker, owing to an increase in the relative area of black stripes, a decrease in orange color values while an increase in brown color values, and an increase in the number of melanocytes in the orange part of the skin tissues. To explore the mechanisms by which TPT induces darker body coloration, the enzymatic activity and gene expression levels of the members of melanocortin system that affect melanin synthesis were evaluated. Leptin levels and lepr expression were found to be increased after TPT exposure, which likely contributed to the increase found in pomc expression and α-melanocyte-stimulating hormone (α-MSH) levels. Then Tyr activity and mc1r, tyr, tyrp1, mitf, and dct were upregulated, ultimately increasing melanin levels. Importantly, RT-qPCR results were consistent with the transcriptome analysis of trends in lepr and pomc expression. Because the orange color values decreased, pterin levels and the pteridine metabolic pathway were also evaluated. The results showed that TPT induced BH4 levels and spr, xdh, and gch1 expression associated with pteridine synthesis decreased, ultimately decreasing the colored pterin content (sepiapterin). We conclude that TPT exposure interferes with the melanocortin system and pteridine metabolic pathway to increase melanin and decrease colored pterin levels, leading to darker body coloration in A. ocellaris. Given the importance of body coloration for the survival and reproduction of reef fishes, studies on the effects of pollutants (others alongside TPT) on body coloration are of high priority.

Exploring the Potential of Nanotechnology in Fisheries and Aquaculture: Opportunities and Implications

Aquaculture has emerged as one of the fastest-growing global food industries in recent years, playing a vital role in meeting the increasing demand for animal protein. However, several challenges, such as disease prevalence, chemical contamination, environmental degradation and inefficient feed utilization, have significantly impeded the sector's ability to contribute effectively to global food security. To address these challenges, considerable efforts have been made to leverage advancements in science and technology within aquaculture. Nanotechnology has emerged as a promising and effective tool to tackle these challenges across various aspects of aquaculture, including fish nutrition, biotechnology, genetics, reproduction, pathology and environmental sustainability. The utilization of emerging nano-materials, such as nano-elements enriched feed, has notably enhanced fish growth and has been applied in aquatic systems to mitigate pollutants, thereby reducing treatment costs. Furthermore, integrating genetically manipulated techniques with nano-biotechnology has led to significant advancements in fish genetics research. Innovative nanotechnology applications, such as nano-sensors, DNA nano-vaccines and drug delivery systems, have revolutionized fish health, reproduction and immune system management. Additionally, nanotechnology is increasingly employed in the fish processing industry to ensure sterile packaging, precise flavoring and high-quality products. Moreover, bio-nano-engineering techniques for optimal utilization of fishery wastes and the implementation of green nanoparticles signify a promising era in post-harvesting practices. This comprehensive review aims to delve into nanotechnology's diverse and good applications in aquaculture, exploring its potential and the challenges it presents.