This work was carried out on "mandi" (Pimelodus darias Bloch) a specie of catfish from Piracicaba river in São Paulo State, Brazil, with the purpose of knowing the influence of the fishing season on moisture, protein, lipids and ash contents of fish flesh, to select the best time to make preserves. The edible part of "mandi" was analysed monthly during a year and showed the following data: moisture 65.15 g/100 g, protein 17.92 g/100 g, lipids 15.51 g/100 g and ash 1.34 g/100 g. The lipids data permitted to classify "mandi" as a fatty fish and june and july were the elected months to pick out fishes for processing.