A comunidade de peixes como base para a avaliação da integridade biótica do rio Tarumã-Açu (Manaus - Amazonas)

Abstract

The Rio Tarumã-Açu is a tributary of the left edge of the Rio Negro, situated the sum of the Manaus city in the Amazon State. The rio Tarumã-Açu conservation is vital for maintenance of the quality of its hidrics resources, however, although its importance, have received little attention of the point of view from studies of ecosystems and little has been reported in relation to this environment. Therefore, this study it had as objective to evaluate the biotic integrity of the rio Tarumã-Açu, using of fish communities. The collections had been carried through with the use of a battery of gill net, during the months of december, april, july and september that correspond to the periods of flood, full, receding and dry, respectively. 353 units of fish, distributed in 82 species, 19 families had been collected and four orders. During the flood, 11 species exclusive, 13 during the full one had been collected, nine during ebb tide and 24 during dry and only one species Hypophthalmus marginatus was common in all the periods of collection. The fishes community of the rio Tarumã-Açu was also analyzed of the point of view of the trofic structure. This analysis is important, therefore alterations in the quality of the environment or the water can affect the availability of the alimentary resources them fish and to provoke alterations in the community. The category most abundant was of the omnivorous, followed for the piscivorous, detritivorous, herbivorous, insectivorous and planctivorous. The Index of Biotic Integrity (IBI) was developed to evaluate the quality of the aquatic resources. Is one about a multimetric index, or either, composition for some metric attributes or of the community of fish, each one of which represents a measurable characteristic of the biological set that dumb in previsible way with the increase or reduction stress it ambient. To evaluate the effect of the ambient alterations, in the rio Tarumã-Açu, some metric ones of the community of fish had been modified and adapted. Space, the average minor of the IBI was gotten in the point next to the estuary of the rio Tarumã-Açu, in the point the sum the average increases significantly and reaches the principle in the third point, in the room point has a small reduction in the value. These results suggest a light change in the quality of the water, to the measure that the river if moves away from the estuary. The integrity classrooms biotic of the rio Tarumã-Açu vary of poor person, in the first point, to regulating in the three following points. In relation to the hydrologic cycle bigger differences in the final value of the IIB had been found, where the classrooms vary during the hydrologic cycle of poor person in the flood to the good one in the full one and in it dries. Although the information in allow them to affirm that the degradation of the basin of the Tarumã is resultant of the disordered growth of Manaus, it is necessary to know better as the ambient modifications, that affect physics, chemistry biological and the waters of the rio Tarumã-Açu, cause a process of gradual degradation, but that it needs to be controlled, therefore, the study of monitoring of water of the rio Tarumã-Açu, on the basis of the Index of Biotic Integrity, was basic to detect space and secular differences of quality of the water and can be enclosed as a useful tool in the development of programs of monitoring in the long run of the Tarumã basin.