The effects of rations with different levels of crude protein on weight, length, alimentary conversion and survival of carps were investigated on a 120-day period (November 19th to March 20th - from 1996 to 1998). The fish were stocked with average weight of 1.38 g and average length of 4.15 cm. with 60 days of age. The experiments followed the experimental outline entirely randomized, in a factorial outline of treatments of 4x2 where four doses of crude protein were tested in two densities of storage (15 and 30 fish per square meter), with four repetitions per treatment. The fish received a daily ration rated in 5% of live weight, which was readjusted every 30 days when all fish were measured and weighed. The behavior of each variable throughout the time for each treatment was studied by polynomial regression analysis. For the overall weight variable, the results obtained using density 15 were: 8.88; 10.23; 10.80 and 11.88g, and with density of 30 were: 5.49; 6.83; 8.06 and 9.19g, respectively for the levels of 20, 27, 34 and 41% of crude protein; the equation that best describes the behavior is Y = 4.23 + 0.27X. For the overall length variable, the results obtained using density 15 were: 8.03; 8.24; 8.54 and 8.98cm, and with density 30: 6,76; 7.11; 7.57 and 7.83 cm, respectively in growing levels of crude protein and the equation that best describes this behavior is Y = 2.80 + 0.08X. The feed conversion variable didn't differ significantly for the different densities. The equation that best describes the behavior regarding the levels of crude protein in the ration is Y = 4.72 - 0.04 X. As a final conclusion it can be affirmed that the effect of densities hadn't influenced the fish growth and the best average of final medium weight was observed in treatment with densities of 15 and 30 fish per square meter with 41% of PB, which suits more the needs of the species at this age.
Common carp; densities; crude protein
