(Growth comparisons of Oreochromis niloticus males on intensive fishculture under two distinct periods of cultivation)

Abstract

This study proposes to verify the economic viability on intensive fishculture experiments of males Oreochromis niloticus, by comparative analyses of the growth and biomass yield, considering two distinct periods of cultivation. There were involved two experiments with male O. niloticus performed in the Fishculture Experimental Station of Pindamonhangaba Fisheries Institute, S. Paulo, Brazil. Experiment I was realized from March/1980 to January/1981 and Experiment II, from September/1985 to July/1986. Other conditions were similar: 100 m² concrete ponds; 2 fish/m² (stocking rate); balanced ration (25% crude protein) supplied daily (1.5% and 3.0% of the biomass during the wintering and the warming times, respectively). Samples of 25% of fish population from each pond were monthly taken for biometry. The average final weights of fishes were 572.0 g (Experiment I) and 588.8 g (Experiment II) and the production of both experiments was practically the same: 105.0 kg/100 m². Economic analyses, considering only the ration expenses, showed profits of US$ 122.80 and US$ 113.90 for Experiment I and II, respectively. The main conclusion of this study is that the special adaptation of O. niloticus in intensive fishculture in Southeast Brazilian region permits that cultures of this species can be realized in different periods of the year, but the highest values of biomass with minimum values of apparent feed conversion coefficient are obtained in shorter period of time when the culture started in Spring periods.