Qualidade da água e composição zooplanctônica em viveiros de piscicultura (Castanhal, Pará).

Abstract

Fishponds as flat artificial systems suffer external and internal influence that go to act in the planktonic community and the factors physicist-chemistries of the water. In this direction, the paper was developed in six ponds and had as objective: to list the zooplanktonic species, to apply quantitative methods, calculating density, relative abundance, wealth, diversity and equitability between the registered organisms and to evaluate the water quality based on the parameters physicist-chemists. Samplings for qualitative and quantitative determination of zooplankton, beyond analyses of temperature, dissolved oxygen, pH, electric conductivity and dissolved total solids had been effected. The dissolved oxygen averages had been above of 6,0mg/l and pH varied of basic the slightly acid one. The conductivity varied of 8,5 the 25,3µS/cm. Had been identified 80 tax, being 60 of Rotifer, three of Protozoa and 17 of Artrhopoda. In density terms, station 06 if detached, being Rotifera the dominant group, with peak in january, 2374.5org/l. In terms of occurrence frequency, the naupliar forms if had detached among copepodes, Cyclestheria hislopi and Alona poppei between the cladocera and Keratella americana e Trichocerca pusilla between the rotifers. Station 01 had the biggest values of diversity and equitabilidity, demonstrating bigger uniformity of species. In this study, the abiotic variable had not varied significantly and were inside of the band recommended for the culture, except the conductivity. The biggest wealth of species and dominance of rotifers allowed to consider them as the group most important of the Station. Copepods and cladocers, for being bigger, had probably been citizens to the visual prerestitution for fish.