Spot Polymorphism and Size Do not Indicate Sex Identity: Implications for the Random Selection Method for Natural Spawning of Spotted Barb (Puntius binotatus) in Pond

摘要

The relationship between the numbers of spot, sex and size of the spotted barb, Puntius binotatus was investigated in order to develop a phenotypic sex identification method for the broodstock management of this species. A total of 77 fish specimens with total length (TL) ranged from 4.0 to 9.6 cm were examined for spot polymorphism (3 spots and 4 spots) and sex. Chi-s square test analysis showed spot polymorphism did not correlate with sex identity. The spot polymorphism appeared in both male and female fish at various sizes. These results suggest that such polymorphism is not a result of the morphological changes during the fish growth. The sex ratio in P. binotatuswas found to be 1: 1.2(male: female). Male reproductive organ (testis) was found fully developed first at TL 4.0 cm while ovary was observed in larger fish (TL 4.95 cm). The present study concluded that the spot polymorphism is not a reliable phenotypic sex identification method. Nevertheless, random selection of at least 77 fish with minimum size 4.0 cmas broodstocks would be sufficient for the natural spawning of P. binotatusin pond.