Comparison of artificial spawning effectiveness of hCG, CPH and GnRHa in combination with dopamine inhibitors in a wild strain of ide Leuciscus idus (L.) in hatchery conditions

Effect of temperature and spawning agents on wild female asp (Leuciscus aspius) reproductive efficiency under controlled conditions

Artificial reproduction is a bottleneck to produce stocking material for many species of freshwater fish. One of these species is the asp, Leuciscus aspius. Research in the field of artificial reproduction of this species is very scarce and often incomplete. There are no breeding protocols specifying optimal environmental conditions and hormonal stimulation for many species of rheophilic cyprinids, including asp. Since the number of natural asp populations is constantly decreasing, it is important to support natural stocks by restocking with high quality stocking material. For this reason, optimized protocols are needed to breed this species under controlled conditions to produce stocking material with high biodiversity and good health. Such an approach will make it possible to maintain the population of natural asp at a constant level. The aim of this study was to develop the protocol of asp artificial reproduction using optimized thermal conditions and appropriate hormonal stimulation. In experiment I, the influence of constant temperature (10.0, 12.0 and 14.0 °C) on the effectiveness of artificial reproduction of asp. In experiment II, the effectiveness of asp reproduction was checked after the application of spawning agents: Ovopel, Ovaprim or a combination of these two agents The obtained results indicate that for the final maturation of oocytes (FOM) and artificial reproduction of asp in controlled conditions, water temperatures of 10-12 °C are the most useful. Under these thermal conditions, the highest percentages of female's ovulation and embryo survival, as well as the percentage of hatching, were obtained. Hormone injections are necessary to perform final oocyte maturation (FOM) in female asp in captivity. All spawning agents used were especially useful for artificial reproduction of asp, however, the best values of the studied indices, such as ovulation rate and embryo survival, were obtained after the application of Ovaprim or the combination of Ovopel and Ovaprim in water temperature at a range of 10-12 °C. It was found that the pH of ovarian fluid may be a preliminary indicator of the biological quality of eggs in asps. The optimal pH value is 8.0-8.4. At pH below 7.4, no viable embryos were observed.

Artificial reproduction of wild and pond-cultured common tench (Tinca tinca) under controlled conditions

The common tench is an important thermophilic freshwater fish used for aquaculture diversification. This species is farmed in ponds as well as caught in the wild in many European and China. Artificial reproduction under controlled conditions is one of the most important part of modern aquaculture. In this study, two experiments were conducted in which the influence of hormonal agents (Ovopel and Ovaprim - experiment I) and the origin of the spawning stock (wild and pond-cultured - experiment II) on the success of reproduction in terms of ovulation rate (%), latency time (h), pseudo-gonadosomatic index (PGSI, %), hatching rate (%), abnormal larvae rate (%), and spawning efficiency coefficient (Se) were examined. While the wild fish could not reproduce in the absence of hormonal treatment with 0 % ovulation rate. In all tested hormonal treatment allowed to obtain high-quality eggs with hatching rates of over 83 %. Significant differences in latency time were observed among groups from different origins, such as differences in ovulation rate (79 % vs. 90 %, for pond-cultured and wild fish, respectively), PGSI (8.2 vs. 8.9), and hatching rate (63.8 % vs. 84.3 %), which showed significantly better quality in fish from the wild than those from pond culture. This means that when spawners of common tench of various origins are available, it is better to choose spawners from natural waters for artificial reproduction.

Artificial reproduction of the indoor-cultured brackish form of maraena whitefish (Coregonus maraena) under recirculated aquaculture system (RAS) conditions

Maraena whitefish (Coregonus maraena) is a promising coldwater aquaculture species, especially in terms of meat quality. This versatile whitefish species, which inhabits both fresh and brackish waters, including the Baltic Sea, offers promising prospects for aquaculture breeding and cultivation. However, the main problem is the lack of availability of spawners of this species. Therefore, in this study, an attempt was made to raise the spawning stock under controlled conditions and then artificially reproduce the fish to obtain high-quality gametes and then larvae. The conducted research showed that successful culture of maraena whitefish spawners is possible under recirculating aquaculture system (RAS) conditions. The application of proper nutrition and manipulation of environmental conditions allowed the breeding of sexually mature whitefish spawners in less than two years in captivity (meat weight 476 g). Through stimulation of environmental conditions (temperature and photoperiod), it was possible to stimulate the final maturation of gametes of the F1 generation of cultured fish. The use of Ovaprim hormonal stimulation induced 100% of females to ovulate within 10 days of injection, compared to 60% of females in the control group. Additionally, the other examined parameters, such as the pseudogonado-somatic index (PGSI: 11.46% vs. 6.80%), fertilization rate (94.2% vs. 60.1%), embryo survival rate (92.6% vs. 41.1%) and embryo survival rate to the eyed-egg-stage (90.0% vs. 28.0), were significantly higher in the hormonally induced group, finally two times and three times, respectively. The mortality rate of spawners, after spawning and within three months of artificial spawning, was extremely low. The results obtained from the study demonstrate the feasibility of culturing the spawning stock of maraena whitefish in captivity and successfully inducing artificial spawning.

Growth Priorities of the Four Riverine Cyprinids during Early Ontogeny

Growth patterns during early development of four species of riverine cyprinids, common dace (Leuciscus leuciscus L.), ide (Leuciscus idus L.), chub (Squalius cephalus L.) and common barbel (Barbus barbus L.), over 30 days of rearing, were analyzed. The study period covered three successive phases of larval development (preflexion, flexion, postflexion) and part of the juvenile development. The growth analysis carried out in the present study shows that significant allometric growth occurred mainly in preferentially localized body parts (head and tail) and was also associated with an increase in body height. The replacement of temporary structures (e.g., fin fold absorption) and the appearance of definitive structures around 21 mm TL (beginning of the juvenile period) corresponds to a stabilization of the relative growth of most parts of the body. This is probably due to the fact that the studied species had completed the most important part of the remodeling process (metamorphosis) and had achieved a body shape that allows juveniles to colonize faster water habitats. The results also indicate that individuals of species that are less developmentally advanced at the time of hatching (common barbel, chub) show greater initial dynamics of change in growth rate than individuals of species whose individuals are more advanced in ontogeny (common dace, ide). In addition, the small differences observed in growth parameters between successive periods analyzed, supported by the results of previous studies on these species, probably reflect the lack of abrupt changes in the behavior and habitat of the species studied.

A novel technique for mass induction of propagation in small fish species: Hormone immersion

Due to the lack of environmental stimuli found in their natural habitat, not all species of tiny fish can reproduce naturally in the conditions of captivity. Silver rasbora (Rasbora argyrotaenia) was used as the model organism in this study, which is the first to successfully use the hormonal technique of immersion to mass induce spawning and spermiation in small fish species. In this study, in order to find out the effect of immersion hormone treatment, two separate experiments in which commercial hormone Ovaprim™ was used for spawning induction and Ovagold™ for spermiation induction were conducted. Four doses of hormones (0.0 mL/L, 0.7 mL/L, 1.4 mL/L, and 2.1 mL/L) were evaluated on 24 females and 40 males in total. According to the experimental findings of female breeders, 1.4 mL/L dose of Ovaprim™ showed best results on latency period (8.67 h) with a total number of eggs (6994 egg) and fertilization rate (99.22 %). In addition, hatching and larval survival rate have also increased. Milt volume and sperm concentration have also seen an increase to 4.25 μL/g bw and 42.71 10⁶ cell/μL respectively at 2.1 mL/L hormone concentration. The best results or responses were obtained by immersion treatments using Ovaprim™ doses of 1.4 mL/L on female and Ovagold™ concentrations of 2.1 mL/L on male. This new technique is a beneficial for breeding small fish species for either commercial or conservational culture condition.

The effectiveness of Ovaprim, Ovopel, and their combinations in artificial reproduction of common rudd Scardinius erythrophthalmus under controlled conditions

In this study, a practical protocol for artificial reproduction was developed for the rudd, Scardinius erythrophthalmus, to help to produce this fish for aquaculture industries and also for restocking programs. For this purpose, the efficiency of different hormonal agents and their combinations for spawning induction of female breeders of rudd was evaluated. Ovulations were stimulated using different treatments as: two injections of Ovaprim (Ova), two injections of Ovopel (Ovo), a priming dose of Ovopel with a resolving dose of Ovaprim (Comb1), a priming dose of Ovaprim with a resolving dose of Ovopel (Comb2), and two injections of sterile 0.9% NaCl solution as a control group. During the study, ovulation success, egg developmental competence as well as the performance of the freshly hatched larvae were recorded. There was no ovulation in females from the control group. In hormone-treated groups, 84-100% of fish ovulated, but no differences were observed in ovulation success (P > 0.05). The shortest latency period in treated fish was recorded in the Ovo group (431.6 degree-hour, P < 0.05). The best results in terms of working fecundity (number of obtained eggs per fish), relative fecundity, fertilization success, hatching rate, and embryo survival up to the eyed stage were achieved in the Ova and Comb1 groups (P < 0.05). Moreover, better survival rates up to the absorbing yolk sac stage and the lowest abnormality of larvae were observed in Ova and Comb1 groups (P < 0.05). There was no significant difference in the incubation time among different groups (P > 0.05). The obtained results indicate that two injections of Ovaprim and/or a priming dose of Ovopel with a resolving dose of Ovaprim are suitable for the artificial reproduction of rudd female breeders. Due to the proper effects and ease of use, two injections of Ovaprim could be recommended for the production of this species for restocking or aquaculture programs.

Effect of Different Activation Solutions and Protein Concentrations on Ide (Leuciscus idus) Sperm Motility Analysis with a CASA System

The purpose of this study was to compare four activation solutions (AS)-Woynarovich, Lahnsteiner, Kucharczyk, and Perchec-with the addition of 0.5% bovine serum albumin (BSA) for ide (Leuciscus idus) sperm activation and analysis with a CASA system. It was found that ide sperm can be activated using each AS within a pH range of 7.4-9.0 and an osmolality range of 160-200 mOsm kg^-1. The effect of Woynarovich and Perchec solutions supplemented with BSA and casein at concentrations of 0.25, 0.5, 1.0, and 2.0% were also analyzed during the experiment. These two AS without protein supplementation (pure solutions) were the controls. Woynarovich and Perchec solutions supplemented with the minimum BSA concentration (i.e., 0.25%) significantly improved sperm motility (89.05% and 86.63%, respectively) compared to the controls (20.39 and 28.48%, respectively). Similar increases were also noted in progressively motile sperm (PRG, %), the curvilinear velocity of sperm (VCL, µm s^-1), and the amplitude of lateral head displacement (ALH, µm). A similar trend in CASA parameters was also noted when casein was added to Woynarovich and Perchec solutions at a concentration of 0.25%. We concluded that 0.25% doses of each of the proteins were sufficient to prevent sperm adhesion to glass slides, and they can be used in research on ide sperm motility measurements.

Expression Patterns and Gonadotropin Regulation of the TGF-β II Receptor (Bmpr2) during Ovarian Development in the Ricefield Eel Monopterus albus

Bmpr2 plays a central role in the regulation of reproductive development in mammals, but its role during ovarian development in fish is still unclear. To ascertain the function of bmpr2 in ovarian development in the ricefield eel, we isolated and characterized the bmpr2 cDNA sequence; the localization of Bmpr2 protein was determined by immunohistochemical staining; and the expression patterns of bmpr2 in ovarian tissue incubated with FSH and hCG in vitro were analyzed. The full-length bmpr2 cDNA was 3311 bp, with 1061 amino acids encoded. Compared to other tissues, bmpr2 was abundantly expressed in the ovary and highly expressed in the early yolk accumulation (EV) stages of the ovary. In addition, a positive signal for Bmpr2 was detected in the cytoplasm of oocytes in primary growth (PG) and EV stages. In vitro, the expression level of gdf9, the ligand of bmpr2, in the 10 ng/mL FSH treatment group was significantly higher after incubation for 4 h than after incubation for different durations. However, bmpr2 expression in the 10 ng/mL FSH treatment group at 2 h, 4 h and 10 h was significantly lower. Importantly, the expression level of bmpr2 and gdf9 in the 100 IU/mL hCG group had similar changes that were significantly decreased at 4 h and 10 h. In summary, Bmpr2 might play a pivotal role in ovarian growth in the ricefield eel, and these results provide a better understanding of the function of bmpr2 in ovarian development and the basic data for further exploration of the regulatory mechanism of gdf9 in oocyte development.

Influence of the source of spawners' origin on oocyte maturity stages and suitability for artificial reproduction of wild pikeperch (Sander lucioperca) females during spawning season

Pikeperch is one of the major new fish species in freshwater aquaculture. Artificial reproduction is difficult in this species, and many aspects require further study. These include synchronization of female maturation, latency time, gamete quality and spawner survival rate. For these reasons, many fish farmers must constantly replenish their spawning pikeperch stock, often with wild fish. Data on the suitability for the reproduction of wild fish obtained in several lakes during the reproduction period were collected in this study. The findings indicated that larger fish (> 1.5 kg BW) and those obtained in larger and deeper lakes (> 12.0 m mean depth vs. < 5.0 m mean depth, respectively, for deep and shallow lakes) were more valuable to fish farmers during the spawning season when they were obtained because a higher percentage of suitability for artificial reproduction and a higher embryo survival rate was observed for them. The mean embryo survival rate was high and was 84.5 ± 3.9 % on the 3rd day after fertilization and 79.7 ± 3.4 % at hatching. Among the group of the smallest females (< 1.5 kg), the highest percentage of nonsynchronous oocyte maturation occurred. This result demonstrated the successful procedure of both artificial reproduction and a successful method for selecting females for spawning.

The Effect of Hormonal Treatment on Selected Sperm Quality Parameters and Sex Steroids in Tropical Cyprinid Bala Shark Balantiocheilos melanopterus

Hormone treatments are routinely employed with bala shark Balantiocheilos melanopterus male broodstock to stimulate the production of high-quality sperm. In the current trial, three spermiation-inducing treatments were evaluated: 20 μg/kg body weight (BW) recombinant hCG; 20 μg/kg BW [D-Ala6, Pro9, NEt]- gonadotropin-releasing hormone (GnRHa) with 20 mg/kg BW metoclopramide; and poly(lactic-co-glycolic acid) (PLGA) microparticles with slow release of 10 μg/kg BW GnRHa. A 0.9% saline AS negative control was also included. Administration of the GnRHa through the form of slow release of PLGA microparticles 24 h after treatment resulted in a significantly higher sperm volume, motility percentage, and total sperm count compared to the control. Injection of GnRHa with metoclopramide induced sperm parameters that did not differ from the control, with the exception of motility percentage. The lowest potency to induce spermiation in bala sharks was in the treatment with recombinant hCG. Both PLGA microparticles and GnRHa with metoclopramide significantly increased blood plasma concentrations of testosterone and 11-ketotestosterone compared to the control. The PLGA microparticle system with continuous release of 10 μg/kg BW GnRHa was the most effective treatment in inducing spermiation in bala sharks.

Diallel Cross Application and Histomolecular Characterization: An Attempt to Develop Reference Stock of Labeo ariza

The objective of the present study was to evaluate the growth performance and genetic variation in diallel crosses of Ariza labeo (Labeo ariza) originating from three geographically separated rivers (Atrai, Jamuna and Kangsha) in Bangladesh. Intra (G1K♀K♂, G2J♀J♂, and G3A♀A♂) and inter (G4K♀A♂, G5K♀J♂, G6A♀K♂, G7A♀J♂, G8J♀K♂, and G9J♀A♂) stocks were produced following diallel cross (sex ratio—1:1 and n = 48; 16 from each river). Reproductive and growth performance, muscle cellularity and genetic variation following genotyping of eight microsatellite markers (Lr1, Lr2, Lr3, Lr22, Lr24, Lr27, Lr28 and Lr29) and analysis of all crossbreeds was performed. The fertilization (95% ± 2.11%), hatching (88% ± 1.03%), and survival rates (82% ± 1.88%) of G4K♀A♂ were higher compared to other groups. With respect to length and weight gains (2.67 ± 0.4 cm and 3.39 ± 0.2 g), SGR (3.23% ± 0.20%), and heterosis (8.87% and 24.74%) G4K♀A♂ was the superior group. A higher number of hyperplastic muscle fibers, mean number of alleles (2.75) and mean observed heterozygosity (0.417) from G4K♀A♂ could be interpreted to mean that G4K♀A♂ comprise better performance efficiency compared to others and are considered for continuing the L. ariza stock improvement program.

Effect of Application of Different Activation Media on Fertilization and Embryo Survival of Northern Pike, (Esox lucius) under Hatchery Conditions

One of the finfish species that European and North American breeders are most interested in is the northern pike, Esox lucius. Artificial reproduction and the production of viable larvae has a huge impact on further culture. The quality of stripped gametes is highly variable. Therefore, it is important to use gametes with maximum efficiency, which has a direct impact on the amount of stocking material produced and therefore on the economics of production. The aim of this study was to compare northern pike fertilization efficiency, expressed as the survival rate of embryos until hatching. In the first experiment, the highest percentage of hatched embryos was observed in groups of eggs fertilized in a saline diluent prepared with deionized water (after reverse osmosis: group D), at 61.2% and 56.5% in the NaCl5-D and NaCl6-D groups, respectively. The highest percentage of hatched embryos in the second experiment was observed in the egg groups activated with Woynarovich solution (V) at 75.5% and 74.7% for V-D (D—deionized water) and V-T (T—tap water), respectively. In all cases, preparing the activation medium using T versus D water resulted in lower fertilization percentages and lower percentages of hatched larvae. At the same time, two variants (V and B1—Billard solution) were tested during mass spawning in three hatcheries using hatchery water (tap water). The results showed that repeatability was the highest when using activation medium B1.

Artificial Reproduction of Blue Bream (Ballerus ballerus L.) as a Conservative Method under Controlled Conditions

Simple Summary

Quite severe biological imbalances have been caused by the often ill-conceived and destructive actions of humans. The natural environment, with its flora and fauna, has been subjected to a strong, direct or indirect, anthropogenic impact. In consequence, the total population of wild animals has been considerably reduced, despite efforts to compensate for these errors and expand the scope of animal legal protection to include endangered species. Many animal populations on the verge of extinction have been saved. These actions are ongoing and embrace endangered species as well as those which may be threatened with extinction in the near future as a result of climate change. The changes affect economically valuable species and those of low value, whose populations are still relatively strong and stable. Pre-emptive protective actions and developing methods for the reproduction and rearing of rare species may ensure their survival when the ecological balance is upset. The blue bream is one such species which should be protected while there is still time.

Abstract

The blue bream Ballerus ballerus (L.) is one of two species of the Ballerus genus occurring in Europe. The biotechnology for its reproduction under controlled conditions needs to be developed to conserve its local populations. Therefore, a range of experiments were performed to obtain valuable gametes from blue bream following hormonal stimulation with carp pituitary homogenate (CPH), Ovopel and Ovaprim. CPH and Ovopel were injected twice and Ovaprim—once, under a pectoral fin. The spawners were inspected 12 h after the last injection, and the gametes were collected. Eggs were collected from spawning females and fertilized with sperm from three males. The smallest number of ovulating blue bream (four females) was obtained from individuals stimulated with Ovaprim. There were six to nine ovulating females in the other groups, accounting for 60–90% of the females in the respective groups. The latency period was the shortest in the spawners stimulated with Ovopel. The fish in this group ovulated 14 h after the hormonal injection. Spawning was synchronized and all females spawned simultaneously. The highest average weight of eggs per fish (75.4 g) was obtained from the females stimulated with Ovopel, whereas the individuals stimulated with Ovaprim provided the smallest average amount of eggs (49.5 g). The study showed that blue bream spawners are not very sensitive to reproduction-related handling under controlled conditions.

Changes in Cadmium Concentration in Muscles, Ovaries, and Eggs of Silver European Eel (Anguilla anguilla) during Maturation under Controlled Conditions

This study determined the contents of cadmium (Cd) in the muscles, ovaries, and eggs of silver female European eels. The analysis of cadmium content was performed on female European eels caught during commercial fishing in freshwater in Warmia and Mazury (Poland), and then subjected to artificial maturation and ovulation processing under controlled conditions. The content of cadmium (Cd) in the tissues was determined by flameless atomic spectrometry using an electrothermal atomizer. The analysis showed statistically significant differences between the cadmium content in the muscles, ovaries, and eggs (p < 0.05) of female European eels. The lowest cadmium content was found in the muscle tissue (0.0012 ± 0.0001 mg kg-1 wet weight) and the highest in eggs (after ovulation) (0.0038 ± 0.0007 mg kg-1 wet weight). Moreover, a relationship was found between the cadmium content in the muscle tissue and the ovaries (R = 0.673; p = 0.0117) in the same fish. The movement of cadmium from tissues to oocytes may indicate a significant problem concerning this heavy metal content in the reproduction of European eel.

Comparison of responses to artificial spawning of ruffe (Gymnocephalus cernua) specimens captured from their natural habitat to those produced in cultured conditions

Although ruffe (Gymnocephalus cernua) are widely distributed in Eurasia, in some regions (i.e., North America) ruffe are considered an invasive species. There have been no reports on artificial reproduction of this species. A study, therefore, was conducted to evaluate reproduction of ruffe with results of specimens captured from their natural habitat and cultured (F₁ generation) specimens being compared. Spawning specimens from both stocks were treated with hormonal preparations: carp pituitary homogenate (CPH), Ovopel, Ovaprim and human chorionic gonadotropin (hCG) and results were analyzed by comparing response to the specimens of control groups. Spermiation outcomes and sperm motility of the captured and cultured ruffe were similar and with all hormonal treatments, there was a slightly greater sperm motility (55.6 %-57.1 %) in comparison to specimens of control groups (46.7 %-47.1 %). For captured specimens, there was no asynchronous development of oocytes, whereas in cultured specimens 32 % of females had asynchronous development of oocytes. The ovulation rate in specimens of all treated groups was 100 %, whereas specimens in the control groups did not reproductively mature and have ovulations. The latency time from time of hormonal treatments to initiation of reproductive functions depended on the spawning agent used and oocyte maturation stage and there was the shortest latency after using CPH and the longest with hCG treatment. The embryo survival and hatching rates varied with use of different hormonal preparations to induce reproduction: greatest hatching rates with hCG treatment (86.4 %-88.9 %), followed by Ovaprim (78.2 %-80.2 %) and least hatching rate with Ovopel and CPH treatments (66.0 %-67.1 % and 64.0 %-66.0 %, respectively).

Optimization of barbel (Barbus Barbus L.) fertilization and effects of ovarian fluid when there are controlled conditions for gamete activations

Fertilization is one of the most important procedures in artificial reproduction and it directly affects the reproduction outcome. When there is optimization of fertilization, there can be a positive effect on subsequent reproductive processes and economic aspects of aquaculture. This study was conducted to determine time for which oocytes and sperm of barbel Barbus barbus retain fertilization capacity following placement in freshwater. Furthermore, the amount of ovarian fluid, excreted by fish during spawning with eggs (OFI; %) was determined, along with the chemical composition and effects on fertilization were determined. Gametes, ovarian fluid, and seminal plasma from barbel spawning specimens of the F₄ generation were used to conduct the study. Ovarian fluid accounted for 14%-68% of contents of the mass released at spawning and post-spawning composition differed depending on whether hormonal treatments were utilized for control of reproduction. There was an association (R² = 0.982; P = 0.000) between the pH of ovarian fluid and the barbel embryo survival rate. There was the greatest survival rate (>60 %) when the pH range of 7.9-8.4 and there was a lesser embryo viability when pH values were lesser or greater than values within this range (P <  0.05). The results from the study indicate that barbel eggs retain fertilization capacity longer (as long as 210 s) after activation by placement in fresh water than spermatozoa (about 30 s).

Gonadal steroid fluctuations and reproduction results of European grayling (Thymallus thymallus L.) from broodstock farmed in a recirculation aquaculture system

The initial experiment of this study was conducted to determine whether sex steroid concentrations varied before, during and after the reproductive season of European grayling (Thymallus thymallus L.) farmed broodstock confined in a recirculation aquaculture system (RAS). The results indicated that the plasma sex steroid (testosterone - T, progesterone - P₄ and estradiol - E₂) concentrations varied (P < 0.05) during these reproductive periods. There were greater concentrations of T, P₄ and E₂ before and during the grayling reproductive season indicating there are important functions of these steroid hormones associated with gonadal maturation, gamete production and reproductive behavior during the spawning period. In the second experiment of this study, the effectiveness of European grayling controlled reproduction treatment regimens was analyzed and there were 34.69 % and 68.18 % having ovulations in the 2 and 3-year-old broodfish, respectively. Of the embryos developing to the eyed-egg stage, there were 3.70 % and 6.87 % derived from eggs of 2- and 3-year-old grayling females, respectively. Proportions of embryos developing from the eyed-egg stage to hatching were 38.1 % and 52.1 % from eggs of 2- and 3-year-old grayling females, respectively, when there was culturing in a RAS. The results indicate that with grayling broodfish there is greater efficacy in induction of reproduction when there is imposing of the controlled reproduction treatment regimen on 3- rather than 2-year-old broodfish.

Effect of hormonal stimulation on captive broodstock maturation, induced breeding and spawning performance of striped snakehead, Channa striata (Bloch, 1793)

In the present study, there was assessment of effects of gonadotropin treatments on broodstock maturation, induced breeding, and spawning outcomes of striped snakehead in captivity. The striped snakehead (n = 128) were equally distributed in four concrete tanks (15 m²) and hormone implants (500 IU human chorionic gonadotropin (hCG)/kg body weight) were inserted intramuscularly and striped snakehead broodstock administered this treatment were confined in two tanks and striped snakehead of a non-implanted group were confined in two tanks. The hormone implanted striped snakehead had a greater (P < 0.05) gonadosomatic index (GSI) and oocyte diameter in comparison to non-implanted striped snakehead. In a subsequent experiment, hCG and carp pituitary homogenate (CPH) were evaluated for inducing breeding. Dosages of hCG used were, 2,000 (T_H1), 3000 (T_H2), and 4000 (T_H3) IU hCG/kg body weight of females. Dosages of CPH were, 20 (T_P1), 30 (T_P2), and 40 (T_P3) mg CPH/kg body weight of females. Males were administered 0.75 of the dosage administered to females. The values for reproductive variables were estimated. Fertilization (89.0 ± 3.0 %) and hatching (92.0 ± 1.0 %) rates were greater (P < 0.05) in the T_H1 group of implanted striped snakehead. Relative fecundity (19,023 ± 2211), as well as fertilization (96.2 ± 2.4 %), and hatching (96.6 ± 1.7 %) rates were greater in the T_P2 group of the implanted striped snakehead. The results from the present study indicate broodstock treated with gonadotropins had greater spawning outcomes which might facilitate mass scale breeding and fertilized egg as well as juvenile production of striped snakehead in captivity.

Using Rutilus rutilus (L.) and Perca fluviatilis (L.) as Bioindicators of the Environmental Condition and Human Health: Lake Łańskie, Poland

The aim of this study was to determine the mercury content and fatty acids profile in roach (Rutilus rutilus L.) and European perch (Perca fluviatilis L.) from Lake Łańskie (Poland). Mercury content was higher in the muscles than other organs in both species (p < 0.05). Mercury accumulates along the food chain of the lake's ecosystem. The value of the bioconcentration factor (BCF) indicated that Hg had accumulated in the highest amounts in muscles and in the other organs as follows: muscles > liver > gills > gonads. The metal pollution index (MPI) and target hazard quotient (THQ) were below 1, which means that these fish are safe for consumers. The values of HIS, GSI and FCF indicators show that both species of fish can be good indicators of water quality and food contamination. There were few differences between fatty acid content in the muscles of perch and roach. Contents of fatty acids having an undesirable dietary effect in humans (OFA-hypercholesterolemic fatty acids) were lower compared to hypocholesterolemic fatty acids (DFA, i.e., the desirable ones). In addition, the lipid quality indices AI and TI in the muscles of fish were at 0.40 and 0.22 (perch) and at 0.35 and 0.22 (roach), respectively. On this basis, it can be concluded that the flesh of the fish studied is beneficial from the health point of view.