the influence of the broodstock´s age in propagation efficiency and reproduction ability of grass carp (ctenopharyngodon idella valencinnes, 1844)

Grass carp is known as one of the most important species among warm water aquaculture in polyculture fish farming in iran. the aims of this study were to evaluate the influence of broodstock´s age on propagation efficiency and reproduction ability. in this study, 4 and 5-year-old male and female broodstocks (4 from each group) were used. the quality of ovule and sperm in grass carp broodstocks were studied. the results showed statistically significant difference in female fishes in terms of fork length, weight, egg diameter, and fecundity (p < 0.05). in addition, significant difference was found respecting the factors of sperm motility and spermatocrit (in 4-year-old broodstocks, the maximum of 93.75 ± 4.03) (p < 0.05). there was also statistically significant difference in terms of the sperm biochemical compositions between the 4 and 5-year-old groups (p < 0.05). there was statistically significant difference in terms of hatching and larvae viability (p < 0.05). the eggs produced from fertilization of 4-year-old males and 5-year-old females had the maximum average of fertilization rate (98%), hatching (94%), and larvae viability (90%). it was concluded that the broodstock´s age is effective on the stages after fertilization. consequently, using 5-year-old females and 4-year-old males in grass carp can improve the stages after fertilization until the incubation stages and the fish propagation centres can benefit from the results of this research in order to increase the quality of produced larvae.