Artificial spawning of female Lithuanian strain B carp (Cyprinus carpio L.) after treatment with carp pituitary homogenate, Ovopel or [d-Tle6, ProNHEt9] GnRH-a (Lecirelin)

The results of reproduction of females from Lithuanian strain B carp after ovulation stimulation with carp pituitary homogenate (CPH; 0.3+2.7 mg kg^?1; group I), Ovopel (1/5+1 pellet kg^?1; group II) or [d ‐Tle⁶, ProNHEt⁹] GnRH‐a (Lecirelin) with metoclopramide (15 μg kg^?1+10 mg kg^?1 respectively; group III) were investigated. The lowest percentage of spawning females (71%) was recorded in the group treated with CPH. In case of Ovopel or Lecirelin induced ovulation, 86% of females spawned. No statistically significant effect of the ovulation stimulator (group) on the weight of eggs was found; however, the highest mean weight of eggs (expressed both in grams and in the percentage of female body weight) was recorded for the group treated with Ovopel (1400 g and 13%). After the treatment with CPH or Lecirelin, the weight of eggs was 1140 g (11%) and 1100 g (10%) respectively. The ovulation stimulator significantly affected the percentage of live embryos after 36 and 48 h incubation of eggs (P≤0.05; P≤0.01). After treatment with [d ‐Tle⁶, ProNHEt⁹] GnRH‐a, eggs of the best quality were obtained and after 36 and 48 h incubation the mean percentages of live embryos were significantly higher than the means calculated for the remaining two groups. No statistically significant differences were found between the percentage of living embryos after 36 and 48 h incubation of groups I and II.     

Artificial spawning of carp, Cyprinus carpio (L.)

The effect of reproduction was investigated on females of Hungarian strain W, French strain F, and their cross‐breed 1X whose ovulation was stimulated with carp pituitary (0.3 mg kg^?1and, after 12 h, 2.7 mg kg^?1) or Ovopel (one‐fifth of a pellet per kg and, after 12 h, one pellet per kg). It was found that in the case of Ovopel treatment, the percentage of spawning females of strain F and the cross‐breed 1X was higher than in the hypophysed fish compared. The applied ovulation stimulators did not significantly affect the weight of obtained eggs, whereas the significant (P ≤ 0.01) effect was recorded with respect to the quality of eggs after 12‐, 24‐, 36‐ and 48‐h of incubation. After Ovopel stimulation, the quality of eggs was better. The origin of the females had no statistically significant effect on the weight of eggs although the yield of eggs from fish of strain W was much smaller than that from females of strain F and the 1X cross‐breed. The interaction between the ovulation stimulator and the provenance of the females was significant (P ≤ 0.05) for the percentage of live embryos after 48‐h of incubation of eggs. Eggs of the best quality (and highest weight) were obtained from fish of strain F and cross‐breed 1X treated with Ovopel. In females of strain F that spawned within 6 and 10 h after the second Ovopel injection, the effect of the ovulation time on the weight of eggs was non‐significant. It was significant with respect to the percentage of egg fertilization and of live embryos after 36‐h of incubation (P ≤ 0.01 and P ≤ 0.05 respectively). The better quality of eggs (and their higher weight) was recorded when this time was shorter.     

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‐Ala6, Pro9NEt) 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.     

Artificial spawning of African catfish Heterobranchus longifilis: differences between the effects on reproduction in females treated with carp pituitary homogenate or Ovopel

The effects of the controlled reproduction of African catfish Heterobranchus longifilis after ovulation stimulation with carp pituitary homogenate (CPH; 4 mg kg^?1; group I) or Ovopel (1/5+1 pellet kg^?1; group II) were investigated. After the application of Ovopel, eggs were obtained from a higher percentage of females than after a CPH treatment (87.5% and 75.0% respectively). The statistically significant (P≤0.05) effect of ovulation stimulator was specified only in the case of the weight of eggs (expressed in grams and in percentage of female body weight), being higher in fish treated with Ovopel compared with CPH‐treated fish (176.02 g, 8.43% and 109.51 g, 5.48%). The quality of eggs expressed in percentage of live embryos after 24 h incubation was higher by 7.5% in fish treated with Ovopel. Latency period did not significantly affect the weight of eggs, fertilization percentage or percentage of living embryos after 24 h of egg incubation. However, the weight of eggs and percentage of living embryos after 24 h incubation were higher in fish spawning after 12 h latency (159.38 g and 85.30%) compared with the weight and quality of eggs obtained from females spawning after 14 h latency (126.15 g and 76.04%).     

Artificial spawning of carp (Cyprinus carpio L.): differences between females of Polish strain 6 and Hungarian strain W treated with carp pituitary homogenate, Ovopel or Dagin

Investigations of the effects of controlled reproduction were conducted on carp females of Polish strain 6 and Hungarian strain W after ovulation stimulation with carp pituitary homogenate (CPH) (0.3 mg+2.7 mg kg^?1 body weight), Ovopel (1/5+1 pellet kg^?1 body weight) or Dagin (1 dose kg^?1 body weight). In both strains, the highest percentage of spawning females was found after the Ovopel treatment. After treatments with CPH and Dagin this percentage did not differ in strain 6; however, after Dagin, it was higher in fish of strain W. After CPH or Ovopel stimulation the females of line 6 yielded eggs of higher weight compared with line W. After the Dagin treatment the weight of eggs obtained from females, both strains was similar but much lower than after the two remaining agents. The quality of eggs expressed both by the percentage of fertilization and that of living embryos after 24 and 36 h incubation was similar in the two strains only in the group treated with Ovopel. After CPH application eggs of better quality were obtained from strain 6 compared with strain W; however, after the treatment with Ovopel, eggs of much better quality were noted in strain W. In general, the best effects of reproduction were recorded in the case of Ovopel and the poorest in that of Dagin. Females of strain 6 yielded eggs of a higher weight but the percentages of spawning females were higher in strain W after each of the applied spawning agents. A new approach to this problem consisted in investigating the interaction between ovulation stimulators and origin of females of fish treated with Dagin.     

Artificial spawning of carp (Cyprinus carpio L.); differences between the effects of reproduction in females of Hungarian, Polish and French origin treated with carp pituitary homogenate or [D-Tle6, ProNHEt9] GnRH (Lecirelin)

The investigation concerned the reproduction effects in carp females of the Hungarian strain 8, Polish strain 2 and French strain F of ovulation stimulation with carp pituitary homogenate (0.3 mg kg^?1 and after 12 h 2.7 mg kg^?1) or [D‐Tle⁶, ProNHEt⁹]GnRH (Lecirelin) with metoclopramide (15 μg kg^?1 and 10 mg kg^?1 respectively). The ovulation stimulators did not affect the weight of eggs (expressed in g and as the percentage of female body weight). However, in the group treated with pituitary homogenate (I) the least‐square means estimated for these parameters were higher than in the group treated with Lecirelin (II). A statistically significant (P≤0.05) difference in the mean percentage of living embryos after 48‐h incubation was observed between groups I and II, with the eggs obtained from females of group I being of better quality. The origin of females significantly (P≤0.05) affected the weight of eggs. The weight of eggs from females of Hungarian strain 8 was higher (P≤0.05) than the weight of eggs of the other two lines. With respect to parameters for egg quality (percentage of fertilized eggs and percentage of living embryos after 24‐, 36‐ and 48‐h incubation), no effect of the origin of females was observed. The interaction between the spawning agent and the origin of the females was not statistically significant with respect to the two parameters for the weight of the eggs. The least‐square means test for the investigated interaction showed that after the application of pituitary homogenate, the weight of eggs obtained from strains 8 and F was similar (respectively 711.2 g and 665.0 g). However, after the application of Lecirelin the females of strain 8 yielded eggs of a high weight (934.3 g) and those of strain F of a very low weight (373.2 g). A statistically significant (P≤0.05) interaction between ovulation stimulator and origin of females was recorded for the percentage of living embryos after 24‐ and 36‐h incubation. A dependence was found between the latency time and the reproduction effects.     

Artificial spawning of European catfish Silurus glanis L.: differences between propagation results after stimulation of ovulation with carp pituitary and Ovopel

The effect of spawning on European catfish females with an average body weight of 5.6 kg and 11.2 kg was investigated, with carp pituitary and Ovopel being used as ovulation stimulators. Ovopel induced ovulation in a higher percentage of females of both smaller and larger body weight. The applied ovulation stimulators did not significantly affect the weight of the obtained eggs. On the other hand, the effect of the stimulators was highly significant (P≤ 0.01) with respect to the percentage of live embryos after 24‐, 48‐ and 56‐h incubation. The fish of greater body weight yielded eggs of a significantly (P≤ 0.05) greater weight, although of poorer quality. The interaction between the ovulation stimulator and female body weight was statistically significant (P≤ 0.05) for the weight of the obtained eggs and highly significant (P≤ 0.01) for the percentage of live embryos after 48‐h incubation. For the percentage of live embryos after 24‐ and 56‐h incubation, the statistical significance (P≤ 0.05) of this interaction was determined. In the case of females of smaller body weight, a statistically significant (P≤ 0.05) phenotypic correlation was found between the percentage of live embryos after 24‐h incubation and that after 48‐h incubation, and also between the percentage of live embryos after 24‐ and 56‐h incubation.     

Artificial spawning of carp (Cyprinus carpio L.): the use of Aquaspawn and carp pituitary to induce ovulation in females of Lithuanian line B

Ovulation stimulation was carried out in carp (Cyprinus carpio L.) females of Lithuanian line B, using carp pituitary (0.3 + 2.7 mg kg^?1), Aquaspawn (0.5 mL kg^?1) and Aquaspawn + carp pituitary (0.3 mL kg^?1 + 2.7 mg kg^?1). The poorest results of reproduction (the lowest percentage of ovulating females, the lowest weight of eggs and their poorest quality) were obtained after double hypophysation. The best results were induced by the application of Aquaspawn alone. The effect of the applied stimulators was statistically non‐significant with respect to the weight of eggs, being highly significant (P ≤ 0.01) with respect to the percentage of fertilized eggs and that of living embryos after 24‐ and 36‐h incubation. The multiple‐regression equations were calculated for the three groups separately. The percentage of living embryos after 36‐h incubation constituted a dependent variable while the mass of females, the mass of eggs, the fertilization percentage and the percentage of living embryos after 24‐h incubation were independent variables. The regression was only significant (P ≤ 0.01) for the group of fish treated with Aquaspawn.     

Artificial spawning of carp Cyprinus carpio L.: differences between the effects on reproduction in females of Israeli strain Dor-70 and its cross-breed treated with carp pituitary and Ovopel

The effects on carp reproduction were investigated in females of the Dor-70 strain and a cross-breed of this line with a Hungarian one of carp pituitary and Ovopel as ovulation stimulators. It was clear that, in the case of the Ovopel treatment, a higher percentage of females spawned, although the weight of eggs obtained was less than that yielded by hypophysed fish, the differences being highly significant (P ≤ 0.01) with respect to the weight in grams and to percentage of female body weight. No statistically significant differences were determined in the quality of eggs, measured by both the fertilization percentage and the percentage of living embryos, obtained after the two stimulators were used. Neither the provenance of females nor the interaction of female provenance and the stimulator has any effect on the traits investigated. The correlation between the percentage of fertilization and the percentage of live embryos was 0.54 for strain Dor-70 and 0.95 for the cross-breed. The multiple regression equations were calculated for strain Dor-70 and for cross-breed 5 separately, where the percentage of living embryos constituted a dependent variable and the mass of a female, mass of eggs in grams and the percentage of fertilization were independent variables. We appraised the regressions as significant for Dor-70 (P ≤ 0.04) and highly significant for the cross-breed (P ≤ 0.0001).     

Characteristics of the reproduction effectiveness of four Hungarian breeding lines of carp Cyprinus carpio (L.)

The effectiveness of reproduction of four Hungarian breeding lines 7, 8, W, and 0 of carp Cyprinus carpio was investigated. The highest percentage of ovulating females after Ovopel stimulation of ovulation (1/5 + 1 pellet kg^?1 BW of females) was found in line 8 (100 %), in line 0, it was 86.21 %, and in lines 7 and W, the respective values were 73.68 and 76.47 %. It was noted that the breeding line significantly (P ≤ 0.05) determined the weight of the eggs (expressed in grams and percentage of female BW), the fertilization percentage, the percentage of living embryos after 24- and 36-h incubation, the total number of eggs, and the number of live embryos after 36-h incubation. The highest weight of eggs was obtained from females of line 7 (1,083.41 g) and line 8 (981.54 g), while the lowest weight was noted in the case of females of line W (804.94 g). The highest number of eggs was found in line 7 (722,300) and in line 8 (654,400). For these lines, the highest number of live embryos (36 h) was also found (624,400 and 622,200, respectively). Within each line investigated, the regression equations were derived in order to predict the weight of eggs (g), percentage of live embryos, and the number of live embryos after 36-h incubation.     

Artificial Spawning of African Catfish,Clarias gariepinus

Abstract

The effects of controlled reproduction of African catfish, Clarias gariepinuswere investigated in an experiment with carp pituitary (at the dose 4 mg/kg body weight) or Ovopel (1 pellet/kg body weight) used as ovulation stimulators. The application of the synthetic stimulator led to the significantly (P≤0.01) greater weight of eggs (expressed in grams and as percentage of female body weight) and to the significantly (P≤0.05) higher quality of eggs after 24-hour incubation as compared with the hypophysation effects. Two categories of females were used in the experiment, i.e., light (mean body weight of 3.75 kg) and heavy (mean body weight of 8.86 kg) fish. The results show that a significantly (P≤0.01) greater weight of eggs (expressed in grams) was obtained from heavier females. The quality of eggs expressed as the percentage of live embryos after 12- and 24-hour incubation was significantly (P≤0.01 and P≤0.05, respectively) higher for lighter females. The higher weight of obtained eggs and their better quality after Ovopel stimulation compared to the weight and quality of eggs obtained after hypophysation allow for the recommendation of this ovulation stimulator for the fish species investigated.     

Artificial spawning of European catfish, Silurus glanis L.: stimulation of ovulation using LHRH-a,Ovaprim and carp pituitary extract

Ovulation was stimulated in four groups of European catfish, Silurus glanis L., using injections of des-Gly¹⁰, [D-Ala⁶]-LHRH Ethylamide (20 μg kg^–1) and pimozide (10 mg kg^–1), Ovaprim (0.33 mL kg^–1), and carp pituitary extract (4 mg kg^–1, in one or two doses). A higher percentage of ovulating females (producing eggs of sufficient quality) was found after the LHRH-a and Ovaprim treatments (100% and 80%) in relation to fish treated with the pituitary extract (60% and 66.67%). The greatest weight of eggs was obtained in the case of repeated hypophysation and LHRH-a (1299.69 and 1298.57 g, respectively), and the smallest after single hypophysation (1144.08 g). After 60 h of incubation, the best quality of eggs was found in the group treated with Ovaprim (62.9% of live embryos) and the poorest in the two groups which underwent hypophysation (50.41% and 50.75%). No statistically significant effect by the ovulation stimulators on the characteristic qualitative and quantitative traits of obtained eggs was ascertained.     

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 (60.3 %) than eggs obtained from the fish stimulated with Ovopel (53.0 %). The data suggest that some form of domestication appeared in ide cultivated for several generations in carp pond.     

Artificial spawning of common tench <Emphasis Type="Italic">Tinca tinca</Emphasis> (Linnaeus, 1758), obtained from wild and domestic stocks

The study encompasses three reproduction seasons. Tench spawners caught during the spawning season originated from carp ponds (domestic stock) and a lake (wild stock). Fish were reproduced under controlled conditions after hormonal stimulation with GnRHa-containing pellets combined with metoclopramide (Ovopel) or carp pituitary homogenate (CPH). As a result of hormonal stimulation, eggs were obtained from a larger number of females originating from the lake (71.7%) than those originating from the pond (58.3%), although no other statistical differences were found. A similar relationship was recorded for the spermatozoa motilities (range from 72 to 76%). The obtained results indicate that both investigated reservoirs are suitable for tench broodstock management due to the fact that synchronization of ovulation among different stocks is easy to achieve. For this purpose, among the tested spawning agents, Ovopel could be recommended as being slightly more effective.     

Artificial spawning of carp Cyprinus carpio L.: differences between the effects on reproduction in females of Polish and Hungarian provenance treated with carp pituitary and (D-Ala6) GnRH ProNHEt (Kobarelin)

Ovulation was stimulated in carp females of Polish and Hungarian provenance using injections of ( d ‐Ala⁶) GnRH ProNHEt (Kobarelin) (20 μg kg^?1) with metoclopramide (10 mg kg^?1) or carp pituitary (3 mg kg^?1). For estimating the effects of the substance stimulating ovulation and of the female provenance, analysis of variance was carried out using the least squares method. It was found that the stimulating substance, provenance and interaction of these factors did not significantly affect the weight of eggs obtained. On the other hand, the stimulating substance, provenance and interaction had a highly significant (P ⩽ 0.0001) effect on the percentages of fertilization and live embryos. Females of Hungarian provenance treated with Kobarelin yielded eggs of much better quality but a smaller weight than after the pituitary treatment. In the case of carp females of Polish provenance, a yield of eggs of smaller weight and very poor quality was noted compared with the weight and quality of eggs obtained after hypophysation.     

Induced out-of-season and seasonal tank spawning and stripping of pike perch (Sander lucioperca L.)

Nine trials were carried out on the induced propagation of pike perch in out‐of‐season as well as in the natural reproduction period. From January till May, periodically, 16–20 pairs were transported to the hatchery, and acclimated to 15–16°C. The following hormonal treatments were used to induce reproduction: carp pituitary homogenate (CP) and human chorionic gonadotropin (hCG) alone or in combination; gonadotrop‐releasing hormone ‘Ovurelin’ (D‐Phe⁶‐LH‐RH) alone or with metaclopramid (MTC); and ‘Ovopel’ [containing des‐Gly¹⁰‐(D‐Ala⁶)‐LH‐RH‐ethylamide and MTC]. The effects of daylight regime, water temperature and the length of the pre‐spawning conditioning period on the reproduction performance were determined. From the 130 hormonally treated pairs, 122 either spawned in tanks or were stripped. There were no differences in the ovulation rate between out‐of‐season (93%) and seasonal (91%) propagation. The developmental stage of the eggs correlated with the latency period, which significantly declined from January till April. The latency period was the shortest in fish treated with hCG and, secondly, with CP. The germinal vesicle migration did not proceed without hormonal treatment, although in some trials breeders were kept at the spawning temperature for 1–2 weeks. The results demonstrate that the pike perch can be successfully induced to spawn about 3 months earlier than its natural spawning season, which allows a significantly prolonged yearly supply of fry.     

Ovulation induction in northern pike Esox lucius L. using different GnRH analogues, Ovaprim, Dagin and carp pituitary

The traditional GnRH analogue treatments applying the chemicals in pure form proved to be ineffective in inducing ovulation in northern pike (Esox lucius L). Neither mGnRHa ([D‐Ala⁶, Pro⁹NEt]‐mGnRH) nor sGnRHa ([D‐Arg⁶, Pro⁹‐Net]‐sGnRH) administered alone or together with pimozide (mGnRHa), metoclopramide (mGnRHa) or domperidone (sGnRHa) induced ovulation in females, whereas in groups receiving a carp pituitary injection most females ovulated. Spawning‐inducing agent Dagin did not induce ovulation, whereas all but one female ovulated in the carp pituitary‐treated group. Treatment with another preparation, Ovaprim, resulted in similar or lower ovulation ratio than treatment with carp pituitary. After the Ovaprim treatment, time to ovulation was not as predictable as after the carp pituitary injection. The mean fertilization rate was relatively low and similar in the groups treated with Ovaprim (54.7 ± 12.3% and 58.7 ± 19.1% for the first and second experiment respectively) and with carp pituitary (53.7 ± 10.5% and 58.9 ± 14.9%). The mean pseudogonadosomatic index (PGSI) was also similar between the Ovaprim‐treated group (14.5 ± 6.1%) and the carp pituitary‐treated one (17.9 ± 4.1%). In the present experiments, treatment with Ovaprim was less effective than that with carp pituitary.     

Effects of Seasonal Variations, Thyroid and Steroid Hormones, and Carp Pituitary Extract on the Artificial Production of Channel Catfish Ictalurus punctatus× Blue Catfish I. furcatus Hybrids

The primary objective was to compare thyroid hormones and levels of carp pituitary extract for the artificial production of female Ictalurus punctatus × male I. furcatus hybrid catfish. The effects of different carp pituitary extract dosage rates (5, 6, 9, and 10 mg/kg), carp pituitary extract (6 and 10 mg/kg) supplemented with the thyroid hormones thyroxine (T₄) and triiodothyronine (T₃), or pregnenolone (DHP) were determined for inducing ovulation of female channel catfish, fertilization of channel catfish eggs with male blue catfish sperm, and hatching rate of these embryos. Hormone treatments thyroxine and tri-iodothyronine with carp pituitary extract, carp pituitary extract alone, and pregnenolone with carp pituitary extract used to artificially produce hybrid catfish were not different in terms of ovulation rates, eggs/kg, fry/kg body weight of female channel catfish, fertilization rates, or hatching rates (P > 0.05). These findings suggest that lower amounts of carp pituitary extract may be used to induce spawn of female channel catfish for production of channel-blue catfish hybrids and the addition of thyroid and steroid hormones is ineffective at the rates used in this study.     

Induction of ovulation in ornamental common carp (Koi, Cyprinus carpio L.) using LHRHa ([d-Ser(tBu)6, Pro9-NEt]-LHRH) combined with haloperidol and carp pituitary extract

The effects of a single injection of mammalian superactive analogue [d ‐Ser(tBu)⁶,Pro⁹‐NEt]‐LHRHa (20 μg/ kg^?1) combined with the dopamine antagonist, haloperidol (HAL, 0.5 mg kg^?1), for induction of ovulation in the koi carp broodstocks were determined under routine hatchery conditions. The results were compared with classic carp pituitary extract (CPE, double injection) application (water temperature 22 °C). Physiological saline (0.7% NaCl)‐injected fish were used as a control group and no ovulation occurred in this group. The spawning ratio was high in the LHRHa+HAL treatment group and in the CPE treatment group (6/7 and 5/7 respectively). The latency period was 14–16 h in the LHRHa+HAL treatment group and 12–14 h in the CPE treatment group (after the second injection). There was no difference between the two ovulating groups with respect to the spawning index (the weight of eggs as a percentage of female body weight) and fertilization rate of eggs (P>0.05). As a result, ovulation can be induced successfully in koi carp broodstocks with 20 μg kg^?1 [d ‐Ser(tBu)⁶,Pro⁹‐NEt]‐LHRHa+0.5 mg kg^?1 HAL treatment in a single injection without decreasing the egg quality. Application of this combination can be useful for hatchery and broodstock management in koi carp culture.     

Induced spawning in bream, Abramis brama (L.), using carp and bream pituitary extract and hCG

Induced spawning in bream, Abramis brama (L), was studied using acetone-dried common carp pituitary (CP) and bream pituitary (BP) with or without the addition of human chorionic gonadotrophin (hCG). The total dose administered to fish was of 5.0 mg kg^?1 BP or 4.0 mg kg^?1 CP with or without 2000-2200 IU hCG kg^?1 for females and 2.5 mg kg^?1 BP or 2.0 mg kg^?1 CP with or without 1000–1100 IU HCG kg^?1 for males. In all male treated groups 100% of spermiation was observed: in females the most effective method was a triple injection with hCG and carp pituitary, resulting in 79% of females ovulated (over 68% of eyed eggs). Biological quality of eggs, expressed as a percentage of eyed eggs, was negatively correlated with time elapsing between resolving (final) injection and ovulation. Spawning success, expressed as a value of S_e (spawning effectiveness coefficient), was higher in fish treated with triple injection.