Title: Induced spawning of koi carp (Cyprinus carpio) using human chorionic gonadotropin and Ovaprim
Koi carp (Cyprinus carpio) is one of the ornamental fish which is under culture and breeding practices in many different countries. The aim of present study was induction of spawning in Koi fish using human chorionic gonadotropin (hCG) and Ovaprim, as a synthetic compound.Completely randomized design, male and female Koi used as follow: 27 male fish (average weight 68±6 g) were randomly allocated to 9 different groups with 3 replicates as follow: 3 groups receiving hCG (500, 1000, 1500 IU/Kg b.w.), 3 groups of fish treated by Ovaprim (0.1, 0.15 and 0.2 ml/Kg b.w.) and 3 different control groups, intact (without injection), injected a dose of physiological saline and propylene glycol as solvent of hCG and Ovaprim respectively. Only one intraperitoan of injection was used for each fish. Different milt characteristics including milt volume, sperm density, motility duration in water and physiological saline and the percentage of motile sperm were analyzed. For female fish, totally, 28 individual (average weight, 80±12 g) were randomly distributed in 9 different groups with 3 roplicates treated by 3 groups injected by hCG at 1000, 2000 and 3000 IU/Kg b.w, 3 group treated by Ovaprim at 0.2, 0.3 and 0.4 ml/Kg b.w, and 3 control groups as described above (for male fish). Female fish were received two injections, 12 h interval, intrapretoneally. Spawning success (as percentage of ovulated fish), latency period, percentage of ovulated eggs based on the body weight, total ovulated egg, and percentage of eyed eggs, hatchability and swim up stages were analyzed. The results showed significant differences in milt volume, sperm density, spermatocrite, motility duration in physiological saline and percentage of motile sperm among different groups (P<0.05). The highest milt volume (18.35 and 16.83 µl/g b.w) were obtained from fish treated by 1500 IU/Kg hCG and 0.2 ml/Kg Ovaprim respectively. The collected milt from fish received 1000 IU/Kg hCG and 0.1 ml/Kg Ovaprim showed the highest sperm density as 26 and 21 × 106 cell/ml respectively. The highest motility duration after activation in physiological saline (60 and 58 s) were observed in fish treated by 1000 IU/Kg hCG and 0.1 ml/Kg Ovaprim, respectively (P < 0.05). For female fish, ovulation was nat occured in control groups. Complete ovulation success was observed in fish treated by 0.2 and 0.3 ml/Kg Ovaprim. The latency period ranged from 8 – 10 hours without any significant differences among different groups (P>0.05). similarly, the number of egg per gram and collected egg as percentage of bady weight were not significantly different among the treated female fish (P>0.05). Although, the highest number of egg per grams (870), and relative working fecundity 98000 egg/Kg b.w. was recorded in fish treated with 2000 IU/Kg hCG. But no fertilization success was observed for eggs collected form hCG treated fish. In groups treated by Ovaprim, the percentage of survival rates till eyed stage, hatching and swim up stages were about 12, 72 and 55% respectively. Based on the results of this study, it could be concluded that a dose of 0.2 ml/kg b.w. Ovaprim would be a useful agent for spawning induction in male and female Koi carp. Hawever, for introduction of optimum dose of Ovaprim, more experiment with the higher number of spawners is suggested.