Comparisons of fecundity and reproductive hormone levels in three populations of Gymnocypris przewalskii

Abstract The naked carp Gymnocypris przewalskii (Kessler, 1876) is the only economical fish in the Lake Qinghai. In order to determine the relationship between spawning behavior, gonadal development and reproductive hormone levels of the naked carp, we surveyed three populations: artificial farming population (AP), freshwater wild population (FP) and saltwater wild population (SP). This study was conducted from August 2016 to June 2017. A total of 339 naked carps were collected by gill net and purse seine. The body length, body weight, age composition, gonadal development were determined by using conventional biological methods. The fecundity statistics were carried out for female individuals whose maturation of gonads exceeded stage IV and four reproductive hormones were detected by ELISA. The results showed that the average body length, body weight and age composition of AP, FP and SP were 293.37 ± 0.43 mm, 345.79 ± 1.52 g, 4+-10+; 306.48 ± 1.10 mm, 363.20 ± 5.21 g, 4+-20+ and 233.25 ± 0.12 mm, 150.36 ± 0.27 g, 3+-11+, respectively. The average absolute fecundity of the SP was lower than that of the other two populations, but the average relative fecundity was higher. Only the reproductive hormones in the SP had the trend of annual variation, during reproduction-peaks, the levels of reproductive hormone peaked in June. In conclusion, only the reproductive hormone levels and the migratory reproductive activities are synchronized, the natural breeding activities of the naked carp can be carried out.