Effects of age on the reproductive performance of different males and females in bighead carp Hypophthalmichthys nobilis (Richardson, 1845)

Abstract

The age of fish can affect reproductive performance in relation to the gamete quality and productivity which might be expected to be changed in older individuals. The consideration can be important in artificial propagation in relation to the selection of broodstock. We determined the age-related changes in male and female reproductive characteristics of the bighead carp Hypophthalmichthys nobilis and then we examined the effects of age on the male and female reproductive fitness in terms of fertilization, hatching, and larvae survival rate. A total of eight 3–4-year-old males and eight 4–5-year-old females were crossed using a factorial breeding design. Fertilization, hatching, and larvae survival rates were counted. We found no significant difference between 3 and 4 year olds in the sperm motility traits, density, and spermatocrit, but significant differences (p < 0.05) were observed in the ionic composition (mainly Na⁺, K⁺, Ca²⁺, Mg²⁺), acid phosphatase, and glucose level. The quantitative characteristics between two age groups (4 and 5-year-olds) of the females showed significant differences (p < 0.05) in total weight of stripped egg, ovarian weight, and relative fecundity, while no significant differences were found in egg size, absolute fecundity, and gonadosomatic index (GSI). In fertilization trials, we found that male age strongly influences fertilization (p < 0.05), embryonic development (p < 0.05), and larval survivability (p < 0.001), while significant female effects, as well as male and female interactions (p < 0.001 for all) were only observed for 7 days post-hatching larval survivability. One-way ANOVA showed significant differences among the fertilization (F = 3.797, p = 0.05), hatching (F = 4.802, p = 0.03), and larvae survival rate (F = 32.94, p = 0.001). Our results suggest that crosses between 4-year-old males and 5-year-old females of bighead carp achieved the best reproductive output.

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