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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.

Elimination of egg stickiness is an important factor in artificial reproduction of pikeperch (Sander lucioperca L.). This study was conducted to evaluate the effectiveness of Alcalase enzyme to remove the adhesive layer of pikeperch eggs. The eggs were treated with Alcalase at 0.5, 1.0, 1.5, 2.0 and 5.0 mL L−1 or a milk/talc solution 2 min post insemination. Duration of exposure was 2 min in Alcalase and 60 min in milk/talc. The highest, albeit not significant, hatching rate (85.4%) was found with 1.5 mL L−1 of Alcalase, but hatching rates were similar in 0.5, 1.0 and 2.0 mL L−1. Hatching rates were significantly lower groups treated with 5.0 mL L−1 Alcalase enzyme (56.4%) compared to groups treated with milk powder and talc (61.3%). Nominally complete removal of adhesiveness was observed in 1.5 and 2 mL L−1. All Alcalase treatments led to significantly lower incubation duration compared with the traditional milk/talc treatment. The application of Alcalase successfully eliminated pikeperch egg stickiness in less time than with traditional milk/clay/talc methods.

This study aimed to compare the fertility of eggs between artificially matured female silver eels that spawned spontaneously and those that were spawned by manual stripping. The effects of the two methods of spawning on ovulation and fertilization rate were also investigated. For this purpose, 18 wild female European els captured in Bonello lagoon (North Adriatic Sea) were carp pituitary extract-injected to undergo sexual maturation and ovulation; a final injection of 17,20b-dihydroxy-4-pregnen-3-one (DHP) was administered when at least 30% of the oocytes were fully transparent. After the DHP-injection, nine eels were transferred to a new closed recirculating aquaculture system, where they were housed with spermiating males (sex ratio 4/1) to allow spontaneous spawning (SPT-group); the remaining nine eels were transferred to a 250 L tank and ovulation was checked at four-hourly intervals by manual stripping (STR-group). The number of eggs per female in the SPT-group was significantly greater than that in the STRgroup. Furthermore, fertilization rates in the SPT-group were notably higher than those observed in the STR-group. Significantly, the best performances were obtained among eels in which at least 50% of oocytes were fully transparent at the time DHP was administered. We conclude that the fertility of eggs from spontaneously spawning eels is superior to that of eggs acquired by strip-spawning and artificial fertilization.

Anaesthetic agents are very useful for reducing the stress caused by handling, sorting, transportation, artificial reproduction, tagging, administration of vaccines and surgical procedures in fish. The efficacy of two anaesthetics: MS-222 and AQUI-S® were tested on rohu, Labeo rohita advanced size fry. The lowest effective doses that produced induction in 3 min or less and recovery times 5 min or less and meet the most criteria of good anaesthetic characteristics were 125 mg L−1 of MS-222, and 30 mg L−1 of AQUI-S® in rohu, Labeo rohita advanced size fry. Induction times were significantly decreased with increased in the concentrations of any of the two tested anaesthetic agents. The lowest doses suitable for transportation of rohu advanced size fry observed were: 10–15 mg L−1 of MS-222 and 2.5 mg L−1 AQUI-S®. Both anaesthetics showed promising to be used as anaesthetics for handling and transportation in rohu (Labeo rohita) advanced fry.

In the study the effects of artificial reproduction of sterlet (Acipenser ruthenus) fed different feed ration were compared. Three doses of feed were used: 1.0%, 0.75% and 0.5% of the fish biomass per day. The results indicate that the feed rations for fish used for caviar production or breeding material should differ. The optimal ration for the quality of sex products and progeny was 0.75% of the fish biomass, whereas in view of the number of maturing fish, the better ration was that of 1% of the fish biomass. In group fed 0.75% of the fish biomass per day the highest GSI value, the largest eggs and hatch and the highest survival to the hatch were noted. The feed ration of 0.5% of the fish biomass was too low, as indicated by the low parameters of eggs obtained, their survival and the smallest number of mature and ovulating females. These results can provide direction for the creation and exploitation of spawner stocks as well as for other sturgeon species cultured under controlled conditions.

An important component of semen examination is the comparison between the characteristics of fresh and stored semen (Lahnsteiner, Berger, Weismann & Patzner 1996). The relationships among the parameters of fresh and cryopreserved semen may be determined to identify markers for prediction of the effectiveness of the cryopreservation procedure for fish semen (Lahnsteiner et al. 1996). As the quality of cryopreserved semen is significantly lower than that of fresh semen, such markers are important for successful cryobanking of fish semen (Piros, Glogowski, Kolman, Rzemieniecki, Domagala, Horvath, Urbanyi & Ciereszko 2002). The handling and storage of gametes is central to many assisted reproductive procedures and may be broadly considered as either short-term storage, at temperatures above 0°C, or long-term storage at temperatures below 0°C. Short-term storage of fish gametes may be necessary when the availability of male and female gametes for in vitro fertilization is asynchronous (Lahnsteiner, Weismann & Patzner 1997) or if the sources of gametes are spatially separated. Preservation may also be necessary during transport to a facility with the capacity to cryopreserve gametes for long-term storage, in certain instances when spermatozoa and oocytes have been removed from moribund or recentlydead animals in the field. Several factors can, however, affect the quality and viability of the stored sperm. In this regard, the assessment of the biochemical characteristics of sperm, particularly in terms of enzyme characteristics, can provide new insights into spermatozoa motility and fertilization ability, thus creating opportunities for improving artificial reproduction and germplasm resource conservation procedures (Li, Hulak & Linhart 2008). The enzymology of fish gametes is not well known, when compared with that associated with mammalian semen. Detailed results of research on the enzymes of fish spermatozoa are available with respect to aspartate aminotransferase (AST), lactate dehydrogenase (LDH), acid phosphatase (AcP), b-N-acetylglucosaminidase (b-N AGase) and arylsulfatase (AS) (Schmehl, Graham & Erdhal 1987; McNiven, Gallant & Richardson 1992; Ciereszko & Dabrowski 1994; Piros et al. 2002;). AS and b-N AGase are among the key enzymes, localized within the mammalian acrosome, that play a pivotal role during penetration of the oocyte (Nikolajczyk & O’Rand 1992; Brandon, Srivastava, Heusner & Fayer-Hosken 1997). The activity of AS and b-N AGase during fertilization in sturgeon can provide useful information regarding speciesspecific fertilization and prevention of polyspermy (when a single egg is fertilized by more than one sperm) as postulated by Cherr and Clark (1985). AcP, one of the enzymes found in sperm, has been described in mammalian spermatozoa and seminal plasma (Yousef, Diamandis, Jung & Diamandis 2001) and has also been observed in spermatozoa

This study was conducted to evaluate the effects of different diet energy levels on animal performance. Specifically, this investigation examined the reproductive and histological aspects of the liver and gonads of female silver catfish (Rhamdia quelen). These fish were fed for 210 days with diets containing 30% digestible protein (DP) and digestible energy (DE) that corresponded to 11.93, 12.98, 14.03, 15.07 and 16.12 MJ of DE kg−1. The initial and final lengths, weights, and weight gains, the visceral, gonadal, and hepatosomatic indices, and the histological parameters hepatocytes area and gonadal stages were evaluated. In the reproductive season, the fish were submitted to an artificial reproduction protocol and the percentage of spawning females and their relative and absolute fecundity were evaluated. DE did not affect reproductive or animal performance aspects (P > 0.05). Cytoplasmic vacuoles in hepatocytes were observed in higher DE levels. Thus, female Rhamdia quelen can be fed a diet of 30% DP with 11.93 MJ of DE kg−1 without reproductive or performance losses.

This study aimed at improving the reproduction effectiveness and synchronization of ovulation in the pikeperch, Sander lucioperca (L.), during induced spawning, which is one of the main bottlenecks in the aquaculture of this species. For this purpose, a new categorization of maturation stages in pre-ovulatory oocytes was applied. It is generally based on two morphological indicators: germinal vesicle migration or its breakdown (GVBD) and different oil droplet coalescence rates. This categorization covered seven stages (from I to VII) – from the end of vitellogenesis to ovulation. The categorization was verified by controlled reproduction with the use of hormonal stimulation (500 IU of hCG per kg of female body weight) and low spawning temperature (12 °C), which extended the latency time. In addition, some morphological indicators (pseudo-gonadosomatic index, Fulton's condition coefficient) of females were calculated in order to determine their usability in determining the maturation stage. However, these indicators proved to be ineffective for this purpose, further highlighting the need to determine the maturational stages in pre-ovulatory oocytes to synchronize ovulation in pikeperch. During the experiment, ovulation seemed to be synchronized among the experimental treatments. Statistical differences were found in terms of latency time between experimental groups at different maturity stages (II – 78–98 h; III – 57–78 h; IV – 48–58 h; V – 32–49 h; VI – 5–30 h) according to the proposed classification. This classification and the results presented in the study significantly improved the synchronization of ovulation, which may positively affect the effectiveness of pikeperch production under controlled conditions.

In order to obtain an appropriate and reliable method for the mass production of Clarias gariepinus (Burchell) fingerlings. experiments on artificial reproduction and pond rearing were carried out in the Republic of Congo in 1987-1991. Reproduction could be induced throughout the year using common carp pituitaries (3 mg kg−1 female). The average relative fecundity of females varied between 1.3%± 0.3 (SEM) and 14.3%±1.3 (SEM). The average hatching percentage of the eggs varied between 28.4%± 4.5 (SEM) and 59.1%± 3.7 (SEM) respectively, in the dry and rainy season. The fluctuation of the relative fecundity as well as the fluctuation of the hatching percentage follows the seasonal fluctuation in rainfall and temperature. The use of a net cage made of mosquito netting (1 m3, 0.5 mm mesh size) and the roots of water hyacinth (E. crassipes) as an egg incubator proved to be reliable. In ponds not protected against frogs an average of 5.0 ± 2.9 (SEM) fingerlings m−2 per 40 days cycle were obtained, whereas in ponds completely surrounded by a wall of aluminium roof plates (0.8 m high) the average production was 32.3 ± 3.3 (SEM) fingerlings nr- per 40 days cycle, when they are stocked with approximately 100 larvae m−2. Increasing the larval stocking density or extending the rearing period did not improve the final production. The main causes of low production in unprotected ponds are competition for food resources due to the presence of phytophagous frog larvae and cannibalism among the fingerlings of Clarias gariepinus. An analysis showed that the system is labour orientated, technically reliable and economically feasible when the fingerlings can be sold for USS 0.07 apiece.