Cantão State Park


   Backwaters of Cantão

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The backwaters of Cantão are the most critical part of its ecosystem.  Its trophic dynamics, namely the import of nutrients – organic matter and fish - is reliant upon the annual floods of lakes and small rivers.  The backwaters of Cantão include oxbow lakes, forest ponds (which dry out completely by the end of the dry season), and hundreds of kilometers of narrow channels which crisscross the delta of the Javaés river. All these waterbodies have in common the fact that during the floods, they are all interconnected as the black waters of the Javaés river rise and flow over the entire landscape, while in the dry season they become isolated from one another.

There are 843 oxbow lakes within the borders of Cantão state park, and about 900 in the Javaés delta as a whole. The entire rest of the Araguaia wetlands contains just over 200 lakes, illustrating the importance of Cantão for the great river's ecosystem. Oxbow lakes are the site of reproduction for many species of fish, and for concentrating 80% of the basin's lakes, Cantão is known as the "nursery of the Araguaia." The peacock bass or tucunaré, one of Brazil's most popular freshwater gamefish, is one of many species which reproduces in the Cantão backwaters during the dry season. Another is the pirarucú, the world's largest freshwater fish, whose numbers are dwindling everywhere in the region due to relentless poaching. The remote and inaccessible lakes of the interior of Cantão are one of the last remaining sanctuaries for this species.

During the floods, almost every aquatic species in the park can be found in the interconnected backwaters. During the dry season, prey fish become concentrated in isolated water bodies, providing a veritable feast for predators like the giant otter, the Amazon river dolphin, the pirarucú, and the black and spectacled cayman. Along lake edges, five species of kingfisher, nine species of heron, and specialists like the Sunbittern and the Green Ibis forage for fish and invertebrates. Neotropical cormorants and Anhingas fish away from the shore. Even jaguars join in the feast, diving into forest pools to catch large fish, or sitting in ambush for them as they pass through the shallow water channels that connect deeper lakes.

The reproductive and nursing cycles of fish in the Araguaia are dependent upon Cantão´s unique system of inner lakes, small rivers and canals.  If this system were ever degraded, there would be a tremendous impoverishment of the park’s ecosystems, resulting in a massive reduction of the populations of aquatic birds and other predators, including several endangered species.  The regional fisheries in the entire mid-Araguaia basin would simply collapse.  Unfortunately this is not an implausible threat: the Bananal Island has by now lost most of its inland lakes, and fisheries have already collapsed near the most densely populated areas.  The prevention of these processes is the absolute priority in the Cantão´s management.