Carp Pituitary Homogenate Research Articles

Attempts for increasing Astyanax altiparanae spawning rates and percentage of responsive oocytes

In this study, we aimed to propose changes in the protocol of cultured Astyanax altiparanae hypophysation to increase the maximum ovulation rate of 60% registered previously. To that two consecutive experiments were conducted. In the first experiment, three carp pituitary homogenate (CPH) doses (3, 6, and 9 mg/kg) were administered in a single injection, while in the second experiment, the 6 mg/kg CPH dose was tested either in single or double injections. In the first experiment, a single injection of 3 mg/kg CPH did not induce final oocyte maturation or spawning, while a dose of 6 mg/kg CPH resulted in an increase in the plasma level of prostaglandin (PGF2α) at ovulation. The single higher dose of 9 mg/kg CPH did not improve reproductive performance and even though anticipated the resumption of meiosis it was detrimental to the spawning rate. In the second experiment, the dose of 6 mg/kg CPH fractionated into two injections led to a higher spawning rate, spawning volume per female body mass, frequency of post-ovulatory complexes, and PGF2α concentration at ovulation compared to the single injection. The most effective treatment remained the 6 mg/kg of CPH fractionated into two injections, but still providing very low proportion of ovulated females (∼40 %). Overall, this study indicates that the spawning protocols for this species need to be improved to induce ovulation in a larger number of females and be more potent in those females that respond positively.

Comparison of different methods of wild vimba bream Vimba vimba (L.) spawning under controlled conditions

This paper describes a study in which different types of the reproduction of wild vimba bream (Vimba vimba) under controlled conditions were compared. Reproduction was performed by using three methods: spontaneous (natural spawning- NS groups): without hormones but with nests, semi-artificial (S groups) with hormones and nests, and artificial (A groups) with hormones and manual stripping of gametes. In groups S and A, different types of hormonal stimulation were tested: common carp pituitary homogenate (CPH), human chorionic gonadotropin (hCG), and commercial pellets containing mammalian GnRHa and dopamine antagonist-metoclopramide (Ovopel). The number of spawning fish, i.e., spermiating males and ovulating females, were compared depending on the type of breeding and the stimulant used. The lowest number of finally matured fish: spermiating males (67 %) and ovulating females (0 %) were noted in the spontaneously reproduced group. The best method of reproducing wild vimba bream under controlled conditions was the semi-artificial approach with hormonal stimulation and spawning nests, where ovulation rates in hormonally treated groups were between 43 % and 71 %, vs 26–57 % in artificial spawning groups. No ovulation observe in control groups in S and A types of reproduction. The highest embryo survival to the eyed-egg-stage was noted in group A-hCG (average 88.2). A higher value of spawning effectiveness (Se) with the use of the same hormones was obtained for groups S (0.374–0.574) than for groups A (0.252–0.493). In both cases, the highest Se was recorded for Ovopel stimulated fish and the lowest in hCG stimulated groups.

The effect of LHRHa with and without dopamine antagonist on reproductive performance in lambari Astyanax altiparanae

The present study evaluated the effect of luteinizing hormone-releasing hormone analogue (LHRHa) with and without dopamine antagonist (i.e., domperidone (D)) on the reproductive performance of lambari females (Astyanax altiparanae) as well as on secretion of 17α-20β-dihydroxy-4-pregnen-3-one (17,20β-P) and prostaglandin F2α (PGF2α)) and on the histological evaluation of ovarian structures in two independent and consecutive experiments. In the first experiment (Exp. 1), five LHRHa doses (20, 60, 180, 540, and 1620 μg/kg BW) were tested with three replicates each, while in the second experiment (Exp. 2) the dose of 180 μg/kg was tested in combination with D at a dose of 20 mg/kg with four replicates. The replicates in both experiments consisted of an experimental unit in which five females and 10 males were placed. In both experiments, two control groups were formed, 0.9% saline (negative control) and 6 mg/kg of carp pituitary homogenate (CPH), and females from all groups received the total dose in two injections (i.e., one comprising 10% of the total dose and a second one 12 h later comprising the resolving dose). There was a decrease in fertilization and hatching rates that coincided with the two highest doses of LHRHa (540 and 1620 μg/kg), suggesting that these doses may have caused hormonal overstimulation affecting egg quality. Taken together, these results were not in favor of an obvious dopaminergic control of final oocyte maturation (FOM) in lambari, since the use of LHRHa associated with D did not improve reproductive performance of lambari compared to LHRHa alone, CPH, and negative control. Plasma levels of 17,20β-P were related to FOM and/or ovulation in most cases. There was not a clear association between ovulation and PGF2α plasma levels. The CPH-treated group was the only one performing better than the negative control, increasing the spawning rate and spawning volume per female body mass as well as triggered FOM in almost all females submitted to hormonal induction, indicating that CPH is the most suitable hormonal therapy to induce FOM and ovulation in lambari (among the treatments tested here).

Characterization of sperm quality in Brycon hilarii: How does morphology affect sperm movement?

Brycon hilarii is a neotropical fish whose population in rivers is being threatened by overfishing, construction of hydroelectric dams, transposition of riverbeds, and pollution. Fundamental knowledge of the reproductive characteristics of this species is necessary to enable its breeding in captivity, for aquaculture as well as for biological conservation. The aim of this study was to investigate and describe the sperm parameters, their correlations, and relevant factors, and how these issues can affect sperm quality in B. hilarii. Sperm was collected after hormonal induction using carp pituitary homogenate. Spermatozoa concentration, total length, motility, and percentage of normal cells were measured to be 2.85 × 109 cells mL−1, 40.28 µm, 68.1%, and 51.6%, respectively. Tail abnormalities were most frequent; however, head abnormalities were closely related to practically all sperm kinetic parameters. Present results suggest that these abnormalities affect motility and movement kinetics, and modifying the pattern of sperm cell movement, sinuosity of movement and vigor. The potential application of this study in aquaculture management of B. hilarii is crucial for the artificial reproduction of fish and represents a significant contribution to the knowledge of its reproductive biology, facilitating the reproduction of the species.

Successive seminal collections from Leiarius marmoratus during the reproductive period

This study aim was to verify whether milt quality of male Leiarius marmoratus is maintained among successive samples collected during the same reproductive period. Ten reproductively mature males were used to evaluate four successive sperm samples collected at 10-day intervals. For these collections, seven males were injected with carp pituitary homogenate (CPH) at a dosage of 3.0 mg/kg body weight, in two applications (30% and 70%), at an interval of 10 h. The other three males were administered only saline (control). Injection with CPH or saline occurred prior to each of the four collections. Only one male from the control group released a small volume of milt (0.33 mL), and only during the first collection period. Of the seven males treated with CPH, five released milt during all four collections. Milt volume of the first sample collected (0.63 mL) did not differ from that of other samples (0.59–1.38 mL; P > 0.05). Sperm concentration was greater in the first samples collected (1.98 × 109 spermatozoa/mL) compared to the other samples (0.35 × 109 at 0.92 × 109 spermatozoa/mL; P < 0.05). Sperm motility, curvilinear velocity, straightness, and morphological normality did not differ among the consecutive samples (P > 0.05). Average path velocity, straight-line velocity, oscillation, linearity, progression, and membrane integrity decreased slightly in the samples collected subsequent to the first sample (P > 0.05). In conclusion, milt quality decreased among successive collections; however, quality of all samples from all collections was sufficient for use for fertilization of oocytes.

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

Simple SummaryQuite 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.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.

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).

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 (TH1), 3000 (TH2), and 4000 (TH3) IU hCG/kg body weight of females. Dosages of CPH were, 20 (TP1), 30 (TP2), and 40 (TP3) 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 TH1 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 TP2 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.

Effects of hormonal treatment on induced spermiation and semen quality in the endangered Amazonian fish Hypancistrus zebra (Siluriformes, Loricariidae)

Reproduction in fish is influenced by several environmental factors. In many cases, failure in reproduction is common once fish are no longer in their natural habitat. Thus, the use of exogenous hormones has been crucial to control the reproductive cycle of many fish species under ex situ conditions. These hormonal stimulations became yet more important for those species facing extinction, as the case of Hypancistrus zebra. Since its habitat has been destroyed, successful reproduction in captivity is a way to ensure species survival. The first phase of this study aimed to test the possibility of getting semen from Hypancistrus zebra without hormonal induction. Two groups of fish (24 each) were subjected to two treatments: hormonal induction with 3 mg kg−1 CPH (carp pituitary homogenate) and spermiation without hormonal induction. In the second phase, was evaluated the effect of hormonal induction on semen quality using gonadorelin (a GnRH synthetic analogue) at doses of 40, 60, 80, 100 and 120 μg kg−1. CPH treatment was used as a positive control and one group of fish was not induced (negative control). Collected semen was assessed for volume, sperm concentration, motility rate, sperm vigor, duration of motility, membrane integrity and spermatozoa morphology. We were able to successfully collect semen from the endangered Hypancistrus zebra without hormonal induction, however when subjected to the hormonal treatment males released a higher volume of semen, with higher quality in some parameters. CPH treatment was more efficient in improving sperm quality in H. zebra, favoring normal sperm morphology, although gonadorelin did not harm it. The minimum effective dose of gonadorelin to increase seminal volume is 100 μg kg−1, which can be applied in a single injection. Information gained from this study will assist semen collection procedures for a germplasm bank formation and other initiatives for conservation of this Amazonian endangered fish species.

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

Optimization of artificial reproduction, by increasing the survival rate of embryos and hatching rate, is of major importance for reducing genetic diversity, especially in fish captured from their natural habitat that subsequently spawn in hatcheries. The artificial reproduction of ide, Leuciscus idus (L.) was conducted in controlled conditions. The spawning agents included: different doses of human chorionic gonadotropin (hCG) that was compared with common carp pituitary homogenate (CPH), Ovopel – a commercial agent for induction of spawning that contains mammalian gonadotropin releasing hormone analogue (mGnRHa) with dopamine antagonists (DA): metoclopramide (MET) and Ovaprim – a commercial agent containing salmon gonadotropin releasing hormone analogue (sGnRHa) and a dopamine antagonists (DA): domperidone (DOM). There were no ovulations in females from control groups. There were no differences between the ovulation rates (90 %) or embryo survival (> 92 %) and hatching rates (> 91 %) when there was administration of hCG doses between 500 and 1000 IU/kg. When there was comparison of different spawning agents, the ovulation rate was 100 % for all treated groups. There were the shortest and longest latency times to the time of ovulation after administration of CPH (26 h) and hCG (79 h), respectively. The greatest embryo survival (> 93 %) and hatching (> 91 %) rates occurred as a result of hCG administration with these values being slightly greater than when there was treatment with Ovaprim. The association between latency time and hatching rate indicated that when there was a slower final oocyte maturation (FOM) there were greater hatching rates.

Effect of different treatment agents and post-treatment latency times on spermiation stimulation of northern pike (Esox lucius) under controlled conditions

The effect of different treatment agents, namely, carp pituitary homogenate (CPH), Ovaprim ([D-Arg6, Pro9NEt]-sGnRH + domperidone) and a dopamine-receptor antagonist (metoclopramide), on the stimulation of northern pike (Esox lucius) spermiation was tested under controlled conditions. To carry out the experiment, males (n = 84) were divided into four groups: control (n = 21); CPH (n = 21); Ovaprim (n = 21); metoclopramide (n = 21). The control group was given 0.9% NaCl but no hormonal treatment. After 24 h, sperm was collected from seven males belonging to control (n = 7), CPH (n = 7), Ovaprim (n = 7) and metoclopramide (n = 7). This procedure was repeated after 48 and 72 h post-treatment. At each time, sperm was collected from seven males from each group only once. After collection, the quantity and quality of sperm were determined. It was confirmed that the treatment agent and latency time (the time between treatment and sperm collection) are two factors affecting the quantity and quality of northern pike sperm collected under controlled conditions. The highest total sperm volume and total sperm production (TSP) were noted in the CPH group compared to the Ovaprim, metoclopramide and control groups. In contrast, the time of sperm collection affected the sperm concentration (SC), TSP and sperm pH. With increasing time, SC and TSP decreased, which indicated the occurrence of sperm hydration being part of the final sperm maturation process. Sperm maturation is in turn a consequence of increases in sperm pH and seminal plasma osmotic pressure between 48 and 72 h post-treatment. Sperm motility and sperm kinetic parameters were affected by treatment agent and the time of sperm collection. This indicates that the sperm’s ability to move that is achieved in the optimal environment (in spermatic ducts) is dependent on both factors which determine sperm maturation in northern pike under controlled condition.

Reproduction of endangered river lamprey (Lampetra fluviatilis) in controlled conditions

The research reported focuses on reproduction of the river lamprey Lampetra fluviatilis,(Linnaeus, 1758) in controlled conditions. There was specific emphasis on fish harvesting dates (autumn and spring), holding conditions and reproduction in a controlled environment. Attempts were also made to synchronize the time of ovulation among river lampreys, egg and sperm collections. Hormonal stimulation was conducted using carp pituitary homogenate (CPH) at a total dose of 4 mg/kg which allowed for shortening of the egg-laying period from 2 to 3 weeks to a few days while sustaining embryo survival rates and larvae quality. River lamprey males were found to not require hormonal treatment to yield good-quality sperm, as measured using the CASA system. River lamprey broodstocks adapted well to different manipulations in hatchery conditions when harvested in the autumn and spring. The results of the present study may be used to restore endangered natural populations of the river lamprey (egg and sperm collection, fertilization or gamete preservation) because ovulation and spermiation synchronization is very difficult to achieve without hormonal treatment in controlled conditions.

Effect of carp pituitary homogenate (CPH) and sGnRHa (Ovaprim) on northern pike (Esox lucius) spermiation stimulation and its effect on quantity and quality of sperm

The effect of carp pituitary homogenate (CPH, n = 7) at a dose of 2.0 mg kg−1 and (D-Arg6, Pro9NET)-sGnRH + domperidone (Ovaprim, n = 7) at a dose of 0.5 ml kg−1 in northern pike (Esox lucius) sperm maturation under controlled conditions was examined. On the control group, 0.9% NaCl at a dose of 1.0 ml kg−1 (n = 7) was used. Sperm was collected 48 h following injection. Sperm quantity (total sperm volume, total sperm production and sperm concentration), sperm motility using the Computer-assisted sperm analysis (CASA) system and sperm and seminal plasma quality (sperm pH, seminal plasma osmotic pressure and seminal plasma pH) were determined for each male separately in each group. The results of the present study demonstrate that hormonal treatment had a positive effect on sperm maturation in northern pike, regardless of the hormonal preparation used. However, even though no differences were found in total sperm volume and total sperm production between fish injected with either CPH or Ovaprim, it should be highlighted that the highest progressive motile sperm (PRG), straight-linear velocity (VSL) and movement linearity (LIN) was noted in fish treated with Ovaprim. It was also found that it is possible to collect sperm from non-hormonally manipulated fish. However, in such a case, only a small sperm volume (around 0.1 ml) characterised by lowered PRG (below 40%) was noted. Considering the fact that only after Ovaprim application sperm motility with progressive movement of sperm above 50% was observed, the hatchery practice of collection of sperm 48 h after its application (at a dose of 0.5 ml kg−1) may be recommended.

Changes in mercury concentration in muscles, ovaries and eggs of European eel during maturation under controlled conditions

The degradation of the environment, namely due to pollution causes increasing impact on the organisms living on it, especially those at the top of the trophic chain. The accumulation of heavy metals such as mercury in live organisms may have a negative effect on the efficiency of reproduction. The aim of this study was to determine the mercury (Hg) content in muscles, ovaries and eggs during final maturation of gametes and after ovulation of European eel females. To this end, 65 (53 as treated and 12 as control) female European eels collected in Poland were analysed for mercury content. Eels were caught during commercial fishing activities in fresh water in the Warmia and Mazury region. Females were stimulated with carp pituitary homogenate (CPH) at 18mgkg−1, at 5-day intervals, for 20 weeks. The hormones were not given to the fish in the control group. The mercury content in tissues was determined by atomic absorption using a Milestone DMA-80 and analysis showed statistically significant differences (P < 0.05) between the content of mercury in muscle, ovary and eggs. The total mercury concentration in females following spawning increased in muscles and ovaries. Female eel eggs (0.0031 ± 0.0003mgkg−1 w/w) were found to contain eight times less mercury than their ovaries (0.026 ± 0.002mgkg−1 w/w) and 78 times less than their muscles (0.24 ± 0.03mgkg−1 w/w). The concentration of mercury in both muscles and ovaries in fish increases after spawning, which can additionally confirm that mercury is transmitted in small amounts from the mother's body to eggs.

Differences in the effectiveness of reproduction among ten breeding strains of the common carp Cyprinus carpio L. after stimulation of ovulation with carp pituitary homogenate or [(D‐Ala 6 , Pro 9 NE t) mGnRH‐a + metoclopramide] (Ovopel)

This study focused on the reproduction effectiveness of 10 breeding strains of common carp (Polish strains 2, 3, 6; Hungarian strains 0, W, 7; Lithuanian strain B; French strain F; Israeli strain D and Yugoslavian strain J) after stimulation of ovulation with carp pituitary homogenate or Ovopel. The percentage of females with recorded ovulation became higher after Ovopel treatment in as many as eight breeding strains (2, 3, 6, 0, W, B, F, D). The interaction between the spawning agent and the breeding strain was statistically significant (P ≤ 0.05) for the mass of spawn and non-significant for traits determining the quality of eggs. Among the 10 breeding strains, in 4 (3, 7, B, J) the least-squares means (LSM) for the weight of egg (g) were higher for fish stimulated with Ovopel. Among the strains tested, in seven (3, W, F, J, 2, 7, B), the LSM for the percentage of living embryos after 36 h incubation were higher for fish treated with Ovopel. The evaluation of reproduction effects based on the values of such parameters as the percentage of ovulating females, weight of eggs (g) and the percentage of live embryos (36 h) showed that after Ovopel treatment the poorer effects were obtained only for strains 6, 0 and D.

The influence of female body weight class on the effectiveness of controlled reproduction of carp Cyprinus carpio Linnaeus, 1758

The effects of Ovopel treatment and hypophysation on five different size classes (age = 4–16 years) of female carp, Cyprinus carpio L., from 10 breeding lines were assessed (class I: >3≤5 kg; class II: >5≤7 kg; class III: >7≤9 kg; class IV: >9≤11 kg; class V: >11 kg). Ovulation stimulation was done with carp pituitary homogenate i.e. CPH (0.3+2.7 mg kg−1 BW) or [(D-Ala6, Pro9-NEt)-mGnRH+metoclopramide] i.e. Ovopel (1/5+1 pellet kg−1 BW). Analysis of variance included the results obtained in controlled spawnings carried out during 15 breeding seasons. The classification according to the body weight classes significantly (P ≤ 0.01) differentiated the weight of eggs (g) obtained both from CPH and Ovopel treated fish, the percentage of viable embryos (36 h) after CPH (P ≤ 0.05), number of eggs after CPH and Ovopel treatment (P ≤ 0.01) and number of living embryos (36 h) calculated per kg−1 CPH treated fish. The lowest weight of eggs was obtained after both the CPH and Ovopel application in class I and the highest in class V. The highest mean for the total number of eggs from CPH treated fish was noted for size classes IV and V and the lowest for class I. From Ovopel treated females the highest mean was noted in classes V and IV and the lowest in class I. The highest mean for the number of live embryos (36 h) calculated per kilogram CPH and Ovopel treated fish was recorded in female weight classes I and II. The lowest mean for this trait was found for size class V after both CPH and Ovopel treatment. The group of hypophysed females provided the best results of reproduction when the body weight was over 7 kg but not exceeding 9 kg (class III). Females treated with Ovopel reached such results when body weight was higher than 9 kg but did not exceed 11 kg (class IV). After both CPH and Ovopel treatment the poorest results were noted in females exceeding 11 kg body weight (class V). The predicted regressions for the number of viable embryos (36 h incubation) obtained per 1 kg female BW allows to determine in which weight class which stimulator offered the best predictability for this trait.

Artificial induction of maturation in female silver eels, Anguilla australis: The benefits of androgen pre-treatment

Abstract 11-Ketotestosterone dramatically affects ovarian physiology in previtellogenic eels, notably increasing lipid accumulation and the expression of the follicle-stimulating hormone receptor. We therefore sought to combine androgen pre-treatment of female silver eels with “traditional” hypophysation in order to assess whether androgens constitute a valuable addition to induced spawning protocols. Eels were first implanted with different doses (0–30 mg) of 17-methyltestosterone to evaluate effects on oocyte size. Females (Trial I) were subsequently subjected to repeated injections with carp pituitary homogenate to artificially induce maturation. In a subsequent trial, we used 1 mg of androgen, implanted in either aromatizable (androstenedione) or non-aromatizable form (11-ketotestosterone) and again induced eels to mature artificially by repeated injections with carp pituitary homogenate. Androgen treatment significantly increased oocyte diameters prior to commencing carp pituitary homogenate treatment. Thereafter, less time, less money and less handling were required to reach the pre-ovulatory stage, while retaining comparable amounts of lipid in ovulated eggs. We contend that androgen pre-treatment has promise as a synchronizing and cost-effective measure for the artificial induction of maturation in anguillid eels.

Changes in European eel ovary development and body and ovary chemistry during stimulated maturation under controlled conditions: preliminary data

This study compared changes in the biochemical composition of muscles and ovaries of maturing female European eels during hormonal stimulation with carp pituitary homogenate under controlled conditions and in the development of oocytes. It has been found that differentiation of oocyte size in eel is visible from the beginning of the gamete maturation process. This differentiation increases as gonads grow. Furthermore, oocytes are at different development stages and are still highly differentiated in terms of size during ovulation. Moreover, the biochemical composition of the body and gonads was found to change. During the process of maturation, the relative fat content in the eel body decreases both in the muscles (from 21.99 ± 4.3 to 18.48 ± 3.3 %) and in gonads (from 25.76 ± 2.71 to 15.21 ± 4.7 %), with the changes in ovaries being more rapid. Protein content in muscles also decreased (from 15.98 ± 3.13 to 12.35 ± 1.6 %) during the process of female maturation. Different trends were observed for polyunsaturated fatty acids (EPA and DHA). The total amount of these acids decreased in muscles (P 0.05).

Changes in Body Weight and Eye Size in Female European Eel Kept in Fresh and Salt Water

The eel is a catadromous fish which spends most of its life in freshwater and adults swim to the Sargasso Sea region to spawn. While preparing for the reproductive process, eels undergo a metamorphosis to become what is called silver eel; a process involving changes in the colour and weight of the body and an increase in the eye size. These are indicators of fish maturity and they facilitate the selection of fish for reproduction under controlled conditions. During this study, changes in the body weight (BW) and eye size in female European eel were observed while being given weekly hormonal injections of 20 mg kg–1 carp pituitary homogenate and kept in 15°C freshwater and in 15°C saltwater with a salinity of 32-33‰. Fish kept in saltwater but not subjected to hormonal stimulation were used as a control group. Furthermore, after the experiment was finished, females in the control group were kept for next 5 months, with the same environmental parameters maintained. Differences between the treated groups were observed as early as week 4 of the experiment. An increase in fish BW was observed in fish kept both in salt and freshwater which were subjected to hormonal stimulation. On the other hand, changes in eye size were observed in the fish kept in saltwater, both in those hormonally stimulated and otherwise. The eye diameter in the fish kept in fresh after hormonal stimulation did not change significantly.

Changes in ide Leuciscus idus (L.) females’ reproductive parameters after stimulation with carp pituitary homogenate (CPH) and Ovopel: the effect of domestication?

Three groups (wild—WS, semi-pond—SPS, and pond-cultured—PS) of ide Leuciscus idus (L.) were examined. Each group consisted of 30 females and 10 males, aged 5-8 years. All groups were stimulated with two agents: carp pituitary homogenate (CPH) and a synthetic hormonal preparation Ovopel. The amount of ovulating females decreased in conjunction with females' domestication level, mainly because of very low efficacy of CPH for pond-reared ide stimulation. The percentage of ovulating females stimulated with Ovopel (97.0 %) was significantly higher comparing to CPH (63.0 %). No significant differences were found in latency time between the groups but spawning synchronization increased in conjunction with ide domestication. The positive correlation between domestication level and latency time, i.e., the higher the domestication level, the higher the latency time, was stated. No significant differences were found in PGSI as well as in total volume of obtained eggs, but groups differed significantly in the number of dry eggs and in number of swollen egg. Significant negative correlation between domestication level and number of swollen eggs, i.e., the higher the domestication level, the lower the number of eggs, was detected. The survival rate at the eyed stage was the highest in WS group (60.4 %) and PS group (57.7 %), and was significantly higher than in SPS group (51.8 %). Eggs obtained after CPH stimulation had higher survival rate at the eyed-egg stage