Impactos ambientais gerados pelos efluentes de pisciculturas em ecossistemas aquáticos, Amazônia oriental

Abstract

The change in water quality caused by the discharge of effluents from fish farms in three tributaries of the Caeté River and wetland natural fields of Bragança-PA, located in the eastern Amazon, was evaluated by monitoring four fish farms in the period between August 2013 to September 2014. The trophic state index (TSI) and the minimum water quality index (IQAmin) through hydrobiological variables determined on the spot and through physical-chemical analysis in the laboratory, the samples of water during the discharge of effluents upstream, downstream and in the drainage point of potentially receiving water bodies in the water supply point for the breeding and nursery system. The data were analyzed by ANOVA criterion and for the analysis of main components-ACP. It was observed that the management adopted in the assessed fish farms favored the change in quality through eutrophication process in all evaluated nurseries, in which, only the nurseries of fish farms P1 and P4 obtained direct influence on the change of water quality in the drainage stations in grasslands of Ponta Areia/P1 by chlorophyll variable and Maniteua River/P4 by the total phosphorus and chlorophyll variable. Thus, we can point out that fish farms developed in the basin of the Caeté river have inadequate environmental management systems that impact on water quality of ponds and possible threats of eutrophication in loco. So, for the environmental sustainability of the tambaqui breeding systems, it is recommended that there is an environmental planning of the fish farms respecting the ecological interactions (polyculture) and effluents discharged into water bodies, reducing the effluents produced without harming the quality of water used and when possible the realization of fish removal without full or partial drainage of effluents especially in the dry season and possible effluent treatment, as well as the use of wetlands.