Crescimento de três linhagens de tilápias Oreochromis spp cultivadas em tanques-rede no açude Poço da Cruz, Ibimirim-PE

Abstract

The growth of tilapia, Oreochromis spp, were evaluated in a intensive culture, from march to June 2003, through the use of twelve 5 m3 cages located at Açude Poço da Cruz (Ibimirim-PE). The experiment was designed to contain three treatments, according to the strains (Nilotica, Vermelha and Chitralada) and four replicates. Tilapia juveniles averaging 58.28, 18.74 and 63.62g, respectively, for each strain were stocked in randomly cages in a density of 600 juveniles/cage. A extruded commercial ration with 36% crude protein was used during the first 19 days, another with 32% for the subsequent 63 days and another one with 28% for the last 14 days of growout phage. Fish growth was followed through fortnightly measurements with approximately 5% of fish population. The main water quality variables were measured during the culture (temperature = 28.25 ± 0.65ºC, pH = 7.63 ± 0.38 and dissolved oxygen = 5.48 ± 0.98 mg/L) maintained adequate to the fishculture. Growth and production data were differents (P≤0.05) among treatments. Nilotica strain grew better than Chitralada than Vermelha, with respectively growth daily of 5.72, 4.60 and 3.23g/day. The final weight and weight gain were higher (P≤0.05) forNilotica (607.71g and 549.43g) than for Chitralada (504.23g and 440.61g) and Vermelha (328.79g and 335.05g). In this culture system it was possible to maintain a reasonable biomass in the cages since the final biomass were 268.68, 271.62 and 177.38Kg/cage, respectively for Nilotica, Chiralada and Vermelha. This represent a biomass of 6.99, 7.63 and 2.25Kg/m3, respectively for each strain. The feed conversion ratio was 1.85 for Nilotica, 1.77 for Chitralada and 1.86 for Vermelha strains. In spite of the fast growth, Nilotica strain showed a lower survival (73.71%) in relation with Vermelha strain, which presented the highest survival (91.29%) and lowest yield. These results shows that the tilapia Chitralada and Nilotica have a good performance for this type of culture are recommended for cage culture in a commercial scale.