Fish Fertilizer Research Articles

Does duckweed (Lemna minor) feed inclusion play a role on growth, feed conversion ratio and reproductive performance (fertilization, hatchability and survivability rates) in omnivorous fish? Evidence in Nile tilapia (Oreochromis niloticus‐Linnaeus, 1758)

AbstractFish feed production is fraught with high costs due to the inclusion of expensive fishmeal and animal proteins that can be sourced from aquatic macrophytes. Limited attempts have been made on use of the latter for fish feed production. Further, the quality of feed given to fish is known to affect its growth and reproductive performance. Role of feeds containing duckweed (Lemna minor) at 0%‐control feed, 10%, 15%, 20% and 25% inclusion levels on growth and reproductive performance of Oreochromis niloticus of size 18 ± 1 g were evaluated for 12 weeks. The fish were fed twice daily at 10% body weight at 9.00 a.m. and 4.00 p.m. Length–weight measurements were done fortnightly using a measuring board and a weighing balance, respectively. Female mouth‐brooding fish were used to evaluate reproductive performance indicators, namely %: fertilization, hatchability and survivability. Data were subjected to one‐way analysis of variance followed by post hoc and polynomial orthogonal analysis to identify L. minor diets with significant differences (p < 0.05). Fish fed on a diet containing 10% L. minor inclusion showed significantly better growth performance and feed conversion ratio than those fed on the control diet. All L. minor diets gave good fish condition factors above 1.0. Fish fed on a diet containing 10% L. minor and those fed on the control gave reasonably high survival rates of 85.55% and 83.33%, respectively, whereas those fed on 20% L. minor produced the same growth performance as control. Orthogonal polynomial analysis for the final weights across the L. minor diets – 0%–25% – showed a cubic polynomial model (p = 0.000), whereas final lengths portrayed a linear inverse significant relationship (p < 0.05). Inclusion of L. minor in the diets resulted to slightly better fertilization, hatchability and survivability rates at 10%, 20% and 15%, respectively. In conclusion, inclusion of L. minor from 10% to 20% in fish feeds is recommended for enhancing growth and reproductive performance of O. niloticus.

Sperm handling and management in the teleost model fish Japanese medaka (Oryzias latipes)

Japanese medaka (Oryzias latipes) has been used as a model organism in different research fields, including reproductive physiology. Sperm motility is the most important marker for male fertility in fish and, thus, reproduction success. However, because of small volume of ejaculate and short motility duration, it is still challenging to manage the sperm collection and analysis in small model fish. In the present study, we aimed to investigate sperm motility and to optimize sperm collection, short-term sperm storage, and cryopreservation in Japanese medaka (Oryzias latipes). Using two different approaches for sperm collection: testes dissection and abdominal massage, different housing conditions and activating the sperm with different activation solutions, we investigated immediate sperm motility. In the second part of this study, we used different osmolalities of immobilization solution, Hank's Balanced Salt Solution (HBSS) for sperm storage at 0, 2 and 3 h after sperm collection. Finally, the sperm were cryopreserved using methanol as cryoprotectant and HBSS as extender at two different osmolalities, and post-thaw sperm motility was investigated. The highest post-activating sperm motility was achieved in the groups activated by the extender at 300 mOsm/kg. The quality of sperm remained unaffected by co-housing with females or with males only. Furthermore, Hanks’ Balanced Salt Solution (HBSS) with an osmolality of 600 mOsm/kg demonstrated its efficacy as a suitable extender for sperm storage, preserving motility and progressivity for 3 h. The highest post-thaw motility was around 35%. There were no significant differences between post-thaw motility in different groups. We also found that post-thaw incubation on ice can maintain the motility of the sperm for up to one hour after thawing.

Fish Emulsions, Cyano-Fertilizer, and Seaweed Extracts Affect Bell Pepper (Capsicum annuum L.) Plant Architecture, Yield, and Fruit Quality

Bell peppers (Capsicum annuum) were grown in a greenhouse to evaluate organic fertilizer and foliar seaweed application effects on plant architecture, yield, and fruit quality. Many organic fertilizers contain phytohormones intrinsically. Hydrolyzed and non-hydrolyzed fish fertilizer and cyano-fertilizer treatments were applied in split applications every 7 days over a 135-day growing period. Control plants received no supplemental N. Each fertilizer treatment received applications of one of two different foliar seaweeds or no foliar seaweed in a 4 × 3 factorial design with three replications. Both hydrolyzed and non-hydrolyzed fish fertilizers and cyano-fertilizer increased the number of branches per plant compared to the N-deficient control. The plants receiving cyano-fertilizer or non-hydrolyzed fish fertilizer yielded more than the N-deficient control, and those treatments received 2–3 times the auxin application as the hydrolyzed fish fertilizer. In addition, the leaves from the plants treated with non-hydrolyzed fish fertilizer contained substantially higher levels of abscisic acid, although no abscisic acid was detected in the fertilizers. Both seaweed products decreased the number of fruits that were “bell”-shaped and increased the number of “long”-shaped fruits. Organic fertilizers are complex matrices of nutrients, phytohormones, and other metabolites, making it very challenging to determine the mechanisms behind the observations.

Star1 gene mutation reveals the essentiality of 11-ketotestosterone and glucocorticoids for male fertility in Nile Tilapia (Oreochromis niloticus)

Steroidogenic acute regulatory protein (Star) plays an essential role in the biosynthesis of corticosteroids and sex steroids by mediating the transport of cholesterol from the outer to the inner membrane of mitochondria. Two duplicated Star genes, namely star1 and star2, have been identified in non-mammalian vertebrates. To investigate the roles of star genes in fish steriodogenesis, we generated two mutation lines of star1−/− and star1−/−/star2−/− in Nile tilapia (Oreochromis niloticus). Previous studies revealed that deficiency of star2 gene caused delayed spermatogenesis, sperm apoptosis and sterility in male tilapia. Our present data revealed that mutation of star genes impaired male fertility. Disordered seminiferous lobules and spermatic duct obstruction were found in the testis of both types of mutants. Moreover, significant decline in semen volume, sperm abnormality and impaired fertility were also detected in star1−/− and star1−/−/star2−/− males. In star1−/− male fish, lipid accumulation, up-regulation of steroidogenic enzymes, and significant decline of androgens were found. Additionally, hyperplasic interrenal cells, elevated steroidogenic gene expression level and decline of serum glucocorticoids were detected in star1 mutants. Intriguingly, either 11-KT or cortisol supplementation successfully rescued the impaired fertility of the star1−/− mutants. Taken together, these results further indicate that Star1 might play critical roles in the production of both 11-KT and glucocorticoids, which are indispensable for the maintenance of male fertility in fish.

Hypogonadotropic hypogonadism in male tilapia lacking a functional rln3b gene

Relaxin 3 is a neuropeptide that plays a crucial role in reproductive functions of mammals. Previous studies have confirmed that rln3a plays an important role in the male reproduction of tilapia. To further understand the significance of its paralogous gene rln3b in male fertility, we generated a homozygous mutant line of rln3b in Nile tilapia. Our findings indicated that rln3b mutation delayed spermatogenesis and led to abnormal testes structure. Knocking out rln3b gene resulted in a decrease in sperm count, sperm motility and male fish fertility. TUNEL detection revealed a small amount of apoptosis in the testes of rln3b−/− male fish at 390 days after hatching (dah). RT-qPCR analysis demonstrated that mutation of rln3b gene caused a significant downregulation of steroid synthesis-related genes such as cyp17a1, cyp11b2, germ cell marker gene, Vasa, and gonadal somatic cell marker genes of amh and amhr2. Furthermore, we found a significant down-regulation of hypothalamic-pituitary-gonadal (HPG) axis-related genes, while a significantly up-regulation of the dopamine synthetase gene in the rln3b−/− male fish. Taken together, our data strongly suggested that Rln3b played a crucial role in the fertility of XY tilapia by regulating HPG axis genes.

Genome-wide analysis of two different regions of brain reveals the molecular changes of fertility related genes in rln3a-/- mutants in male Nile tilapia (Oreochromis niloticus)

Relaxin3 (rln3) has been associated with various emotional and cognitive processes, including stress, anxiety, learning, memory, motivational behavior, and circadian rhythm. Notably, previous report revealed that Rln3a played an indispensable role in testicular development and male fertility in Nile tilapia (Oreochromis niloticus). However, the underlying molecular mechanisms remain largely unknown. We found that Rln3a is expressed exclusively in the diencephalon* (Di*) of the brain. Deficiency of Rln3a resulted in a significant increase in serum dopamine level and an upregulation of gene expression of gnrh1 and kisspeptin2. To further elucidate the role of Rln3a in fish fertility, we collected two different regions of Di* and hypothalamus (Hyp) tissues for subsequent RNA-seq analysis of both wild-type (rln3a+/+) and rln3a-/- male tilapia. Upon the transcriptomic data, 1136 and 755 differentially expressed genes (DEGs) were identified in the Di* and Hyp tissues, respectively. In Di*, the up-regulated genes were enriched in circadian rhythm, chemical carcinogenesis, while the down-regulated genes were enriched in type II diabetes mellitus, dopaminergic synapse, and other pathways. In Hyp, the up-regulated genes were enriched in circadian rhythm, pyrimidine metabolism, while the down-regulated genes were enriched in type I diabetes mellitus, autoimmune thyroid disease, and other pathways. Subsequently, the results of both qRT-PCR and FISH assays highlighted a pronounced up-regulation of core circadian rhythm genes, cry1b and per3, whereas genes such as clocka, clockb, and arntl exhibited down-regulation. Furthermore, the genes associated with dopamine biosynthesis were significantly increased in the Hyp. In summary, the mutation of rln3a in male tilapia resulted in notable changes in circadian rhythm and disease-linked signaling pathways in the Di* and Hyp. These changes might account for the fertility defects observed in rln3a-/- male mutants in tilapia.

New insights into the role of myostatin in fish fertility based on the findings in mstnb-deficient Nile tilapia (Oreochromis niloticus)

Myostatin (Mstn) was reported to be involved in multiple biological processes including the regulation of skeletal muscle growth, lipid metabolism and reproduction in vertebrates, therefore, it might play an essential role in the fine balance between growth and reproduction. In order to clarify the roles of Mstn in fish reproduction, we systematically investigated the gonadal development and fertility of mstnb mutants in Nile tilapia (Orochromis niloticus). In the present study, mstnb was found to be expressed in the different cell types of gonads by fluorescence in situ hybridization (FISH). Mutation of mstnb resulted in excessive proliferation of phase II follicles in the ovaries while the numbers of phase III follicles were significantly reduced at 210 days after hatching (dah). Interestingly, significant decline of cyp19a1a gene expression, the serum 17β-estradiol (E2), vitellogenin (VTG) were detected at 210 dah. At 360 dah, the ovarian development of mstnb-/- XX tilapia was partially recovered and female fish spawn regularly, however, they were subfertile and produced the poor-quality eggs with significantly lower offspring survival rate. The dramatic up-regulation of cyp19a1a gene expression and serum E2 level at 360 dah might account for the recovery of ovarian development. In mstnb-/- males, excessive proliferation of spermatogonia and retardation of testicular differentiation were found throughout the whole development stages. In mstnb-/- males, evident declines of gonadosomatic index (GSI), cyp11b2 gene expression, and 11-Ketotestosterone (11-KT) were detected at 210 dah, while the mRNA level of cyp11b2 and serum 11-KT level were significantly upregulated at 360 dah. However, mstnb-/- males were infertile since mutation of mstnb gene led to excessive increase of apoptosis of testicular cells and spermiation obstacle. Taken together, these results indicated that Mstn might be an essential regulator for the maintenance of fish fertility.

A juxtaposition of the effects of natural and chemical fertilizers on Ocimum basilicum

Fertilizers can act as a lifeline to farms in areas with low nutrient levels or provide a boost to crops in otherwise well-off areas. One of the biggest decisions a farmer has to make when it comes to fertilizing is whether to use chemical or natural fertilizer. In this study, we applied two unique fertilizers of both varieties to Ocimum basilicum (basil) plants to determine which fertilizer best aided plant growth. We grew basil over the course of 40 days in multiple experiments. We recorded measurements of plant height, leaf length, and leaf width three times each week. We originally hypothesized that the plants treated with chemical fertilizers would have better growth in each of the measurement categories than the plants treated with natural fertilizers. There was no significant difference between Miracle-Gro and fish fertilizer for plant height and leaf length, but there was for leaf width. We also found the plants treated with chicken manure to be significantly smaller than those treated with JR Peters in each of the three categories. Results indicated that natural fertilizers provided no apparent benefit to plant growth, while chemical fertilizers performed slightly better but did not result in increased plant growth over no fertilization.

Fish in Traditional Hezhe Culture

Representatives of the Hezhe people (Nanai people) live in Russia and China. This article is about fish in their traditional culture. Fish and everything related to it can be considered a cultural symbol of the Hezhe people. This is due to the peculiarities of the culture of the region located along the Amur, Sungari and Ussuri rivers. Analyses of historical documents and artistic works show the great importance of working with fish skin in the life of the Hezhe. Material production and spiritual life of the Hezhe have been closely connected with fish for many generations. It has been revealed that the high fertility of fish, one of the main sources of food and material for sewing clothes, caused the Hezhe people to revere fish in ancient times. It has been established that the Hezhe people had a rich culture. Fish became one of the most widespread zoomorphic motifs of Hezhe ornamental art. The image of fish on the products was given a high cultural meaning. This image left a vivid trace in both Chinese and Russian culture — from totemism to decorative items. The article presents an analysis of fish as a cultural symbol based on the materials of Chinese and Russian museum collections. The study of fish in the traditional culture of Hezhe will expand the existing knowledge about the nature and specificity of ethno-cultural interaction between China and the peoples of the Amur region for many centuries. An attempt is made to tell about the specifics of Chinese cultural meaning of decorative items based on fish skin. For the first time the authors treat the ornamentation of fish patterns in the traditional culture of Hezhe in a systematized form. This will allow researchers to familiarize themselves with information from Chinese sources to identify typical images of fish in Hezhe for further study of the topic of fish skin processing as art in Russia.

Influence of Soil and Nutrient Management Practices on Crop Productivity and Quality in High Tunnel Organic Leafy Green Production

Despite the growing interest in high tunnel organic vegetable production, limited information is available regarding optimizing nutrient management for organic leafy greens. This 3-year study examined the impacts of cowpea cover crop as well as different organic fertilizers and composts on yield, leaf mineral nutrient content, and phytochemical properties of organic leafy greens produced in high tunnels under Florida sandy soil conditions. The experiment was arranged in a split-split-plot design with three replications. The whole plots consisted of a cowpea (Vigna unguiculata ‘Iron & Clay’) cover crop and a weedy fallow control, with fertilization treatments in the subplots, including preplant application of granular fertilizer vs. weekly injection of liquid fish fertilizer at the same seasonal rates of nitrogen (112 kg/ha), phosphorus (9.8 kg/ha), and potassium (74.4 kg/ha). The sub-subplots included yard waste-based compost (22.4 Mt/ha), cow manure-based compost (22.4 Mt/ha), vermicompost (5.6 Mt/ha), and no compost control. Cowpea was broadcasted (112 kg/ha) in early July or mid-August and terminated 51 to 53 days after seeding. Pac choi (Brassica rapa var. chinensis ‘Mei Qing Choi’) was transplanted in mid-Sep. or mid-Oct. and harvested after 33 to 36 days. Baby spinach (Spinacia oleracea ‘Corvair’) or baby leaf lettuce (Lactuca sativa ‘Outredgeous’) was direct seeded subsequently as a catch crop. Each experimental unit remained in the same location across the 3 years of the study. Cover cropping had little influence on yields, leaf mineral nutrients, ascorbic acid content, total phenolics, and total antioxidant capacity of pac choi and baby spinach/lettuce. Compared with preplant application of the granular organic fertilizer, weekly liquid organic fertigation improved pac choi marketable yield and dry weight by 16.8% and 5.4% on average, respectively, and enhanced leaf nitrogen and phosphorus contents on a dry weight basis. Relative to the no compost control, yard waste compost consistently improved marketable yields of pac choi by 11.6% on average and led to higher yields of the baby spinach/lettuce catch crop in years 1 and 3, suggesting that compost applications may enhance seasonal nutrient availability to better meet crop demand. However, compost application exhibited inconsistent effects on crop mineral nutrient and phytochemical contents across the years, which could be attributed to the different nutrient compositions of the composts applied in each season, as well as the legacy effects from the previous season. Furthermore, the compost benefits may be influenced by the fertilization program as indicated by their interaction effects observed in this study.

Increased Yield of Three Shallot Varieties from Seed with Addition of Liquid Organic Fertilizer in the Highlands

Shallots are a vegetable commodity that is considered used as a spice in cooking, so the need of the consumer is high. To supply this high consumption is needed increased productivity. Productivity can be increased by using varieties suitable for the growing environment, quality seeds, and proper fertilization. One of the uses of quality seeds is from seeds, but to obtain high production from seeds, appropriate fertilization is necessary. The goal of the study is to establish the liquid organic fertilizers type and the shallot variety from true shallot seed (TSS) can increase yield in the highlands. This research was conducted in IP2TP Berastagi, with a height of 1340 m asl and andisol. This study was conducted from May to September 2018. The Randomized Block Design factorial was used as a research design with 3 replications. The first factor is liquid organic fertilizer (LOF): Without LOF, Rabbit manure LOF, Fish fertilizer LOF, and Fish LOF. The second factor is shallot varieties from seed: Bima, Trisula, and Tuktuk. The results showed that the growth of shallots had no effect in giving liquid organic fertilizer to the seeds. The Trisula shallot variety can adapt to grow and produce well in highlands, while the Tuk-tuk variety is only adapted for growth and the Bima variety is less adaptive for growth and yield. The Trisula shallot variety with rabbit manure liquid organic fertilizer was able to give the best results compared to other treatment combinations (increased the yield by 13.70 – 65.10%.). The Trisula variety can be recommended for planting in highlands by utilizing LOF of rabbit manure.

PENGARUH PEMAPARAN LASERPUNKTUR PADA TINGKAT (KEBUNTINGAN) KETEBALAN PERUT DAN FERTILISASI IKAN TAWES (PUNTIUS JAVANICUS)

Tawes fish (Puntius javanicus) is a freshwater fish that is easy to cultivate but tawes fish can spawn naturally only during the rainy season. Meanwhile, the market demand for tawes is increasing and the availability of seeds is not enough to meet market demand. To overcome this problem, it is necessary to apply technological advances in the form of a biostimulator for the development of Tawes fish farming business. The biostimulator used is a laser. Several studies state that the application of the use of soft lasers can be used to accelerate gonadal maturation. The purpose of this study was to determine the level of fertility and fertilization of tawes fish (Puntius javanicus), as well as to determine the level of abdominal thickness after laserpuncture exposure to prospective female parents. The method used in this study was an experimental method with a completely randomized design. This study consisted of 5 treatments with 1 control with each treatment being repeated 3 times, laserpuncture exposure treatment in 2/6 parts of the body once a week for 1 month. Treatment duration of exposure to laserpuncture for 2 seconds, 4 seconds, 6 seconds, 8 seconds and control. The results showed that exposure to different laserpuncture beams gave highly significant different results on the fertility of tawes fish. The best treatment was exposure to laserpuncture for 6 seconds with a fertilization value of 95.20%. The water quality during the study was within normal limits for tawes life which included a temperature of 27.80C, dissolved oxygen (DO) of 7.58 mg/l and a pH of 7.65.

Optimizing Organic Carrot (Daucus carota var. sativus) Yield and Quality Using Fish Emulsions, Cyanobacterial Fertilizer, and Seaweed Extracts

Liquid fertilizers are often used in the middle of the growing season in an attempt to enhance organic carrot (Daucus carota var. sativus) yield and quality, although their effect on plant performance is unproven. The impact of liquid organic fertilizers and foliar seaweed applications on carrot yield and quality characteristics were evaluated on certified organic land at the Colorado State University Horticulture Field Research Center in Fort Collins, CO, USA, in 2014 and 2015. Hydrolyzed and non-hydrolyzed fish fertilizer and cyanobacterial fertilizer (cyano-fertilizer) treatments were applied through a drip irrigation system at prescribed N rates about every 10 days throughout the growing season. Each treatment, including the unfertilized control, was repeated with the addition of concentrated organic seaweed extract, containing phytohormones, applied foliarly at the manufacturer’s recommended rates. The cyano-fertilizer treatment resulted in longer carrots in 2014 and the highest carrot yield in both years, with it consistently yielding equal to or greater than either hydrolyzed or non-hydrolyzed fish fertilizer. The foliar seaweed applications had no effect on carrot yield in either year. The cyano-fertilizer performed comparably to the other fertilizers, suggesting that cyano-fertilizer could be a viable alternative to organic liquid fish fertilizers.

Embryonic benzophenone-3 exposure inhibited fertility in later-life female zebrafish and altered developmental morphology in offspring embryos.

Benzophenone-3 (BP3), an organic UV filter widely used in personal care products, is ubiquitous in aquatic environments. Previous studies have shown that BP3 can interfere with oocytes development in the ovary. The current study was conducted to evaluate the effects of embryonic BP3 exposure on reproductive outcomes in later life. Zebrafish embryos were exposed to different concentrations of BP3 (0, 1, 10, 100 μg/L) for 5 days in the developmental stage and subsequently fed for 4 months without any toxins. The body length, body weight, and ovary weight in F0 female adult zebrafish and morphology indices in F1 offspring embryos were measured. The reproductive behaviors of adult zebrafish were recorded by a digital camera. HE staining was used to estimate the development of oocytes and the proportion of different phases was calculated. qPCR was used to detect the expression levels of reproduction-related genes of the hypothalamic-pituitary-gonadal (HPG) axis. Our findings revealed that the body length and body weight were not changed with embryonic BP3 exposure, but BP3 exposure inhibited the development and maturation of ovaries in later-life female zebrafish, accompanied by an increased proportion of follicles in the primary growth and early vitellogenic stages, and a decline in the full-growth stage in ovaries. Meanwhile, reduced egg production, delayed hatching rate, altered somite count and increased mortality rate were observed at 100 μg/L in offspring embryos. Behavioral results showed that BP3 exposure reduced the frequency of chasing, touching, entering the spawning area, and the duration of fish entering the spawning area later in life, qPCR analysis showed that the expression levels of reproduction-related genes of the HPG axis were downregulated in females, following a decreasing trend in plasma E2 and 11-KT levels. These results suggested that embryonic BP3 exposure negatively affected the fertility of fish and the development of their offspring embryos, which may cause potential risks to aquatic ecosystems and human health.

Increasing the quantity and quality of potatoes by utilizing seed size and fish organic fertilizer

Potato plants are one of the vegetables that are in great demand by consumers so they have high economic value and needs. The fulfillment of high needs must be accompanied by increased productivity. Increased potato production can be done, among others, by the use of seeds and proper fertilization. This study aims to determine the use of seed size and addition of fish organic fertilizer with inorganic fertilizer efficiency in increasing potato growth and yield. The study is carried out from June until September 2019 in research and assessment installation of agricultural technology, Dolat Rayat District, Karo Regency. The research placed altitude is ± 1,340 m above sea level, and the soil type is Andisol. The research design is a factorial randomized block and consists of three replications. The first-factor treatment is seed size (big >20 g, medium 5-20 g, small <5 g). The second factor is a fish organic fertilizer with efficiency inorganic fertilizer (100% inorganic fertilizer, 50% fish organic fertilizer + 75% inorganic fertilizer, 100% fish organic fertilizer + 50% inorganic fertilizer, and 150% fish organic fertilizer + 25% inorganic fertilizer). The result showed that big and medium seed sizes were able to increase potato growth and yield. Big and medium seed sizes were able to increase plant height by 11.06% and 9.63%, 5,73%, and 4,64% canopy width, 7.30%, and 11.10% leaf area index, and 12.62% and 25.06% yields from small seed size. Adding fish fertilizer with inorganic fertilizer efficiency resulted in growth and yield which is no different from the application of 100% inorganic fertilizer.

Рибницько-біологічна та продуктивна характеристика плідників дунайського лосося (Hucho hucho Linnaeus, 1758) в умовах ДУ «Рибоводний форелевий завод ”Лопушно”»

Purpose. Study and improvement of the reproduction technology of Danube salmon under artificial conditions. Research and analysis of morphological and reproductive parameters of brood Danube salmon reared on artificial feeds. Methodology. The work describes the generalized results of studies carried out during 2018–2020. Morphological and reproductive parameters of brood Danube salmon reared in ponds of the trout farm “Lopushno” were investigated. Healthy age-6-8 brood fish grown using certified specialized artificial feeds of European manufacturers were used for the study. Brood fish were fed with high-protein feed of the Danish manufacturer Efico Alfa 717 (particle size of 6 mm). Findings. The body weight of age-6 Danube salmon females had a wide range of fluctuations ranging from 1700 to 3700 g; body length ranged from 62 to 78 cm, respectively. The limits of fluctuations in body weight in males were from 1850 to 3400 g, in body length from 61 to 78 cm. The average weight of age-7 brood Danube salmon used in spawning was 3331.3 g, and the average length was 74.9 cm. The limits of variation in weight for males were from 2600 to 4850 g, for females – from 2350 to 3500 g; in length: females ranged from 66 to 78 cm, males ranged from 67 to 84 cm. Average weight gain of brood fish was 553 g per year. The body length to height ratio in age-6 brood fish was 6.1 and was higher than in 2019 in age-7 brood fish (5.1), age-6 fish were more oblong. The condition factor in age-6 fish was 0.69, in age-7 fish 0.77 units. The collection of eggs from age-6-7 brood fish was carried out without stimulation. The results of reproductive parameters in age-6-7 females were as follows: the working fertility in age-6 fish ranged from 5882 to 7794 eggs, working fertility in age-7 fish ranged from 6958 to 8671 eggs, relative fecundity in age-6 females had a high result: on average, it was 3219 eggs versus age-7 fish - 2552 eggs. The average weight of age-8 brood Danube salmon used in spawning was 3890.3 g with an average length of 76 cm. The limits of weight fluctuations: in males were 3300–4800 g, in females – 3000–4500 g; in length: 72-82 cm and 72-80 cm, respectively. The analysis of reproductive parameters of age-8 females showed that their average working fertility was 10,980 eggs. Compared to age-8-9 females from natural water bodies, the average working fertility of females grown in artificial conditions was 20% higher. Originality. The monitoring of linear and weight growth of brood Danube salmon of different ages in artificial conditions was carried out. A comprehensive mechanism of scientific principles and methodical recommendations for the artificial reproduction of Danube salmon in order to preserve its abundance in the water network of the Carpathian region has been developed. Practical value. The obtained results can be used to improve the technology of reproduction of salmonids in artificial conditions. Key words: brood Danube salmon, working fecundity, relative fecundity, State Enterprise Trout Farm “Lopushno”.

Biological structure and abundance dynamics of Pacific rainbow smelt Osmerus dentex (Osmeridae) of the Amur river

Data on spawning migrations, biology and abundance of the spawning group of the pacific rainbow smelt Osmerus dentex of the Amur River in the period from 2014 to 2021 are presented. According to the data of mass labeling of producers, the smelt extracted in the Amur estuary and the Amur riverbed belongs to one unit of stock, the migration routes of producers and the spawning rate have been clarified, and a decrease in the number of spawning herds has been recorded. Analysis of the main biological indicators revealed a significantly significant (p<0.001) decrease in size and mass characteristics, a change in age structure, and a tendency to increase the proportion of females in the spawning herd. The analysis of fertility dynamics revealed a decrease in the indicators of individual and relative fertility of fish of the spawning herd in 2017 (p<0,001), however, in general, the observed changes fit into the range of average long-term fluctuations.

Cyp17a2 is involved in testicular development and fertility in male Nile tilapia, Oreochromis niloticus.

Steroid hormones play an essential role in many reproductive processes of vertebrates. Previous studies revealed that teleost-specific Cyp17a2 (cytochrome P450 family 17 subfamily a 2) might be required for the production of cortisol in the head-kidney and 17α,20β-dihydroxy-4-pregnen-3-one (DHP) in ovary during oocyte maturation. However, the role of Cyp17a2 in male reproduction remains to be largely unknown. The aim of this study was to explore the essentiality of cyp17a2 gene in male steroidogenesis, spermatogenesis, and male fertility. A homozygous mutation line of cyp17a2 gene was constructed in tilapia by CRISPR/Cas9 gene editing technology. The expression level of germ cell and meiosis-related genes and steroidogenic enzymes were detected by qRT-PCR, IHC, and Western blotting. EIA and LC-MS/MS assays were used to measure the steroid production levels. And sperm quality was examined by Sperm Quality Analyzer software. In this study, cyp17a2 gene mutation resulted in the significant decline of serum DHP and cortisol levels. On the contrary, significant increases in intermediate products of cortisol and DHP were found in cyp17a2-/- male fish. The deficiency of cyp17a2 led to the arrest of meiotic initiation in male fish revealing as the reduction of the expression of germ cell-related genes (vasa, piwil, oct4) and meiosis-related genes (spo11 and sycp3) by 90 dah. Afterwards, spermatogenesis was gradually recovered with the development of testis in cyp17a2-/- males, but it showed a lower sperm motility and reduced fertility compared to cyp17a2+/+ XY fish. Deletion of cyp17a2 led to the abnormal upregulation of steroidogenic enzymes for cortisol production in the head-kidney. Moreover, unaltered serum androgens and estrogens, as well as unchanged related steroidogenic enzymes were found in the testis of cyp17a2-/- male fish. This study proved that, for the fist time, Cyp17a2 is indispensable for cortisol and DHP production, and cyp17a2 deficiency associated curtailed meiotic initiation and subfertility suggesting the essentiality of DHP and cortisol in the male fertility of fish.

Tetraspanin Cd9b plays a role in fertility in zebrafish.

In mice, CD9 expression on the egg is required for efficient sperm-egg fusion and no effects on ovulation or male fertility are observed in CD9 null animals. Here we show that cd9b knockout zebrafish also appear to have fertility defects. In contrast to mice, fewer eggs were laid by cd9b knockout zebrafish pairs and, of the eggs laid, a lower percentage were fertilised. These effects could not be linked to primordial germ cell numbers or migration as these were not altered in the cd9b mutants. The decrease in egg numbers could be rescued by exchanging either cd9b knockout partner, male or female, for a wildtype partner. However, the fertilisation defect was only rescued by crossing a cd9b knockout female with a wildtype male. To exclude effects of mating behaviour we analysed clutch size and fertilisation using in vitro fertilisation techniques. Number of eggs and fertilisation rates were significantly reduced in the cd9b mutants suggesting the fertility defects are not solely due to courtship behaviours. Our results indicate that CD9 plays a more complex role in fish fertility than in mammals, with effects in both males and females.

The germ cell-specific RNA binding protein RBM46 is essential for spermatogonial differentiation in mice.

Control over gene expression is exerted, in multiple stages of spermatogenesis, at the post-transcriptional level by RNA binding proteins (RBPs). We identify here an essential role in mammalian spermatogenesis and male fertility for ‘RNA binding protein 46’ (RBM46). A highly evolutionarily conserved gene, Rbm46 is also essential for fertility in both flies and fish. We found Rbm46 expression was restricted to the mouse germline, detectable in males in the cytoplasm of premeiotic spermatogonia and meiotic spermatocytes. To define its requirement for spermatogenesis, we generated Rbm46 knockout (KO, Rbm46-/-) mice; although male Rbm46-/- mice were viable and appeared grossly normal, they were infertile. Testes from adult Rbm46-/- mice were small, with seminiferous tubules containing only Sertoli cells and few undifferentiated spermatogonia. Using genome-wide unbiased high throughput assays RNA-seq and ‘enhanced crosslinking immunoprecipitation’ coupled with RNA-seq (eCLIP-seq), we discovered RBM46 could bind, via a U-rich conserved consensus sequence, to a cohort of mRNAs encoding proteins required for completion of differentiation and subsequent meiotic initiation. In summary, our studies support an essential role for RBM46 in regulating target mRNAs during spermatogonia differentiation prior to the commitment to meiosis in mice.