A comparative study of reproductive characteristics among different spawning stocks of naked carp Gymnocypris przewalskii

Abstract:

From July 2017 to June 2018, a total of 295 naked carp Gymnocypris przewalskii, which were used for comparative study of reproductive characteristics, were collected from Erhai, Dahu, and the estuaries of Heima River, Quanji River, Shaliu River, and Buha River in Qinghai Lake. With the exception of the Quanji estuary, spawning stock, sex ratios (female to male, SR) in all locations showed more female than male individuals (i.e., SR>1). The biological minimum size (BMS) of naked carp differed among spawning stocks, and all males reached sexual maturity at a smaller size compared with the females. The smallest BMS of female and male individuals, whose age, total length, and body weight, respectively was 5 y, 157 mm, and 42.5 g, and 4 y, 124 mm, and 24.5 g, was found in the Buha and Shaliu estuary stocks. The gonadosomatic index (GSI) of female naked carp was significantly higher than that of the males for each spawning stock (P<0.05). The GSI of Shaliu estuary female fish (19.67±1.36)% was significantly higher than that of Erhai (10.28±1.36)% and Dahu (13.35±1.24)% fish (P<0.05). However, the GSI of male fish did not differ significantly among the six stocks (P>0.05). Mean total fecundity (Ft) and relative fecundity (Fr) varied from (3338.18±324.25) eggs/female and (21.88±2.10) eggs/g Wb (from Heima estuary) to (10699.40±613.91) eggs/female and (82.68±4.63) eggs/g Wb (from Shaliu estuary), and significant differences were observed in both Ft and Fr between these two stocks (P<0.05). According to these results, the reproductive characteristics of naked carp in Qinghai Lake show a differentiation trend, with differentiation among different spawning populations already visible. The present study can provide potential data for a more accurate fish stocking and fisheries management plan, including stock optimization, enhancement, and release schedules, for naked carp.