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Abstract

Water transparency of Macrobrachium amazonicum ponds under different feeding regimens and selective harvests. In aquaculture systems, water transparency is affected by water supply, feeding rate and fertilization. A study was conducted from December 19, 2003 to May 12, 2004 for a period of approximately 120 days. Twelve 0.01ha earthen ponds were used with 1m deep water. Prawns were fed commercial diet at a rate of 7 to 9% of biomass until the 14th week. Then, three groups of three ponds were fed with 3%, 5% and 7% of prawn biomass. The remaining three other ponds were subjected to combined harvest. The amount of penetrating light was calculated according to Lambert’s Law, described as Iz = Ioe-kz. Evaluation of the data using Kruskall-Wallis, complemented by LSD test, showed a signifi cant difference between treatments of 3 and 5% (p < 0.05). The Mann-Whitney Test was also used for selective harvest and no difference was observed between treatments. The percentage of light absorbed was generally greater than 90%. With regard to the water
layers, the surface and bottom were examined for temperature, pH and dissolved oxygen, but no statistically signifi cant difference was found between the two zones (p > 0.05).