Ecological integrity and fisheries ecology of the Araguaia—Tocantins River Basin, Brazil

Abstract

An attempt is made to evaluate the present environmental impacts of the Tucurui dam on the fisheries and ecological integrity of the Araguaia-Tocantins basin. Management and research needs to minimize the impacts from future hydroprojects and increased human activities in the basin are also addressed. The Tocantins and Araguaia fish fauna is not especially rich by Amazonian standards (about 300 species). Total yields are also rather low (about 8800 t/y) in a river stretch of about 2500 km and unique for being concentrated (90%) in the main channel. Fisheries are heavily dependent on migratory fish and may be severely damaged as a consequence of river regulation. Downstream from the Tucurui Dam important fisheries have been drastically reduced (70%), probably by recruitment failure, lower productivity and overfishing. Upstream from the dam, however, fisheries have benefited from the higher productivity of the artificial lake, although this has not compensated for the regional economic shortages. Management based on 'basinwise' catch statistics and fish migration research should take account of likely future disruptions of commercial fisheries by the synergistic effects of other planned impoundments, mining, deforestation and uncontrolled sport fisheries in the middle and upper basins. extended the colonization frontier to the uplands. This resulted in unprecedented geographical and socio-economic modifications throughout the basin (Almeida, 1986), with serious consequences to the fisheries. This paper appraises the present and projected environmental impacts on fisheries in an attempt to help planners to implement environmentally sound resource use programmes in the basin. Most information presented herein was gathered by literature review, from field observations the authors have made in the last six years and from interviewing more than 90 experienced fishermen in 25 cities scattered along the basin. This is the first product of a research programme on fish migrations in the basin.

Changes in the fish fauna and fisheries in the Slovak section of the Danube River: a review

“…The Gabcíkovo case confirmed the well known effects of river damming and engineering works upon fish and fisheries (e.g., , 1984a, Welcomme 1985, Holcík 1990, Jankovic 1996, Ribeiro et al 1995, Petrere 1996. The main effects of river regulation (which first affected the hydrological regime) were the loss of the pulse effect of floods, the modification of the chemical composition and thermal regime of the water, and the blocking of fish migration.…”

Ichthyofauna, fish supply and fishermen activities on the mid-Tocantins River, Maranhão State, Brazil

“…were the main species and practically dominated the fisheries at mid-Tocantins. Since the Tucurui closure in 1984, those fisheries were benefitted by an increase in their populations during the first years of the reservoir, but Ribeiro et al (1995) identify at that time richness of large size fishes produced in the interior of the reservoir. For this author Prochilodus nigricans captures almost doubled and Semaprochilodus brama increased almost fourfold, later decreasing as the reservoir aged.…”

A pesca no reservatório da hidrelétrica de Balbina (Amazonas, Brasil)

“…Em Tucuruí, a produção de pescado é estimada em 5 kg/ha/ano (Ribeiro et al, 1995), ou seja, quase o dobro da verificada no reservatório de Balbina, que é de 1,2 a 3,1 kg/ha/ano. Em Itaipu, a produção é ainda maior, em torno de 12 kg/ha/ ano (Petrere Jr., 1996).…”