Laguna El Rodeo

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studied reproduction and growth of Heterandria bimaculata in "El Rodeo" lake Morelos, Mexico, from December 1986 through December 1987. A total of 1 452 specimens were obtained (monthly samples). Females represented 60.12 %, males 34.98 % and the young 4.89 % of the population. Overall sex ratio was 1.7: 1 in favor of females (c d p<0.05). The size at first reproduction for females was 27 mm and for males 22 mm (standard lengths); multiple spawning occured throughout the reproductive cycle (from March through May and July through October) primarily, during the rainy season. There was evidence of breeding activity throughout the year. In July the gonadosomatic index mean was highest (4.7%). The number of embryos in the ovaries were between 5 and 78, with a mean fertility of 23, the fertility was associated with standard length with determination coefficients above 93.22 percent. There was a direct relationship between specimen length and weight, and the asymptotic size for males was 64 mm and for females 81 mm (standard lengths).