Effects of adult sex ratio on larvae number and survival of fry in Xiphophorus maculatus (Cyprinodontiformes: Poeciliidae)

In this study, differing adult sex ratios of the Southern platyfish, Xiphophorus maculatus were examined for fish larval number and the survival of fish fry. Sixty adult individuals of X. maculatus were randomly divided into 5 equal groups with various male to female sex ratios of 1:1, 1:2, 1:3, 2:1, and 3:1, respectively. After a month when the male and female fish were kept together in different experimental groups, all the female fish became pregnant. Four different factors in each group were recorded - notably the length of pregnancy, number of fry produced, number of live fry after 40 days, and final percentage survival. According to the analyzed data, the number of fry, the number of surviving fry after 40 days, and the percentage survival were significantly higher in the first group with a male to female sex ratio of 1:1 than the other experimental groups. Our results suggest that the best sex ratio for maximum efficiency is 1:1.