Fishing modification due to dam, pollution and introduction fish species in the Tiete River, SP, Brazil

摘要

The aim of the present study is to examine the modification on fishing in the Tiete river in consequence of pollution, damming up and of introduction of species. The results revealed modification on utilization of fishing equipment. Before the dam used innumerous equipment such as gillnets, cast net and long line, etc. After the dam, dominated the gillnets and cast net. Another important point is the reduction on professional fishing and the increase of sport fishing in consequence of the reduced fish catching and of the biggest profit of other activities. A clear change in the composition of fish caught during long years was observed, with the predominance of rheophilic species as Salminus maxillosus, Prochilodus lineatus and Pseudoplatystoma corruscans before damming up and its reduction after it. Evidences show that until 1960 the refined fish caught that includes species as Salminus maxilosus, Piaractus mesopotamicus and Pseudoplatystoma corruscans dominated fishing. Since 1961 to popular fish caught (Pimelodus maculatus, Hoplias malabaricus and Astyanax altiparanae) started to dominate. The introduction of at least twelve exotic species was recorded, the most common being Plagioscion squamosissimus, Cichla sp and Tilapia rendalli being the Plagioscion squamosissimus the most frequent specie caught in the medium and low part of the river. The fishing also has been suffering influence of pollution and deforestation. In the upper Tiete river the fishing is inexistent for its water are totally polluted. The deforestation contributed for some species, mainly the frugivorous, such as Brycon orbygnianus to become scarce in the Tiete river.