Impact of the activity of the fish farming in the Basin of Ribeira de Iguape River, SP - Brazil

Abstract

With the objective of to verify the impact of the activity of the fish farming in water courses of the Basin of Ribeira de Iguape River, SP, through the evaluation of physical and chemical water characteristics, 40 fish farmings located in eight cities of the region had been visited: Juquiá, Registro, Sete Barras, Miracatu, Pariquera-açu, Jacupiranga, Iguape and Cananéia. The supplying waters and the effluents, launched into the water bodies after the rearing activities, were analyzed during the period of July to December 2001, and the values of nine limnological parameters had been registered. Through Test "t†of Student, it was demonstrated that the characteristics of the effluents were different from those of the supplying waters, with high values of nutrients, such as total phosphorus, ammonia, nitrate and total nitrogen. In accordance with the limnological characteristics, the fishfarms had been grouped (aglomerative hierarchic grouping) as follows: group 1) small fishfarms, which produce up to 10 ton of fish per year; group 2) fishfarms for fishing activities, with weekly additions of few amounts of ration; group 3) big fishfarms, with intensive rearing, which produce around 150 ton of fish per year, and use of great amounts of ration; and group 4) fishfarms, whose supplying waters were already altered. It could be observed that the big fishfarms (group 3) were more impactant than the smaller ones and those for fishing activities (p < 0.01). Forty-one species of exotic species (deriving from other countries) and species proceeding from other river basins had been listed. In 95% of the visited fishfarms, escapes of species to rivers had been registered. It was possible to verify the rearing of six groups of native fish species in the Basin of Ribeira de Iguape River, SP, which constitute a food of high nutritional value and generate jobs for the local community.