중남미

In this study, the growth of Oreochromis niloticus both mixed sex and males sexually reversed were analyzed in concrete ponds in the FES Zaragoza, UNAM, under the environmental conditions of the Mexico City. The experiment was carried from May to November 2013, in two concrete ponds of 50 m2. Similar feeding regime and stocking density of fish were maintained for the culture systems. Different growth parameters like body weight, length, daily weight gain (DWG), specific growth rate (SGR), feed conversion rate (FCR), Fulton’s condition index (K) and survival were analyzed during six months culture period. It was found that culture with monosex males tilapias yielded the highest weight, length, DWG and SGR compared to mixed sex populations tilapias. Water quality was monitored along the experiment. Based on the results, there were statistically significant differences in size (W = 20942.5, p < 0.05) and weight (W = 21413.0, p < 0.05) between the divisions of the pond. The initial total length used was 1.2 cm and ended with 20.4 cm for monosex males, higher than mixed-sex population. The initial average body weight of the fish was 0.21 g and they recorded 192.2 g at the end of culture for monosex males. The weight-length relationship for both populations of fish was positive allometric. The percentage gain in body weight and total length averaged were 150% and 31.8% respectively. Specific growth rates in weight and length for monosex males were higher than mixed-sex population. Daily weight gain and size was similar in both populations. The FCR had a mean value of 1.9:1 for monosex males and condition factor (K) had an average of 1.45 for mixed-sex population. Water quality indicated good oxygenation (>5 mg/L), warm water (>20°C), productive (<100 mg/L CaCO3) and slightly basic (pH > 8). Acceptable growth of fish and a yield of 3 ton/ha/6 months were obtained in both two ponds; therefore, the culture of tilapia under conditions of Mexico City was recommended.