Avaliação do papel do pulso de inundação sobre a riqueza e biodiversidade de peixes em ambiente inundável, no sistema de baías caiçara, porção norte do Pantanal Matogrossense, alto Paraguai
Muniz, Claumir Cesar
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The present study was aimed to assess the role of the flood pulse related to the composition of the ichthyofauna of the Caiçara Basin System (Upper Baía Caiçara/UBC e Lower Baía Caiçara/LBC) in a pantanal environment, in Cáceres, Mato Grosso. 90,041 specimens were collected from September 2005 to September 2007, distributed in two classes, 8 orders, 32 families and 171 species, with 145 of them occurring in both environments. Characiforms, Siluriforms and Gymnotiforms were the most representative orders accounting for more than 90% of all the species obtained in the sampled environments. The UBC, with 155 collected species, considering the two sampled cycles, obtained 68 and 81 constant species, accounting for 50 and 56% of the total species in this bay. In the LBC, with 161 sampled species, the constant species were most significant, with respectively 43 and 56% per cycle and 54 species for the entire sampling period. Odontostilbe pequira, Serrapinnus calliurus and Moenkhausia dichroura were abundant in all the periods. M. dichroura was the most abundant species in practically all the periods and environments. Cyphocharax gillii and Hypoptopoma inexspectatum (detritivores) were abundant in the ebb tide and dry periods. Acestrorhynchus pantaneiro and Roeboides prognathus were the most abundant piscivores in the ebb tide period. Hemiodus orthonops was abundant in the flood and high tide periods. Among the invertivores/insectivores, M. dichroura and O. pequira were abundant in all the seasonal periods. Concomitantly to the fish collection, data from the limnological variables in the two sampled environments were also obtained, which showed significant differences between the seasonal periods. In the dry periods, the UBC remained totally disconnected from the Paraguay River, and the BCI obtained a smaller water amount from the main channel. In the flood period the connectivity between the UBC and the Paraguay River was reestablished. The concentration of dissolved oxygen varied from 0.67 to 5.94 mg/l in BCS and 0.64 and 5.87 mg/l in the LBC. The highest water temperatures were observed during the flood period (31.35 °C) and the lowest temperature during the dry period (22.33°C). Concerning electrical conductivity, the highest values were observed in the flood period (84.19 μS.cm-1). The lowest values were obtained in the ebb tide period (23.30 μS.cm-1). It obtained the lowest pH values (5.66) in the high tide period, and the highest pH values (7.50) in the dry period. Characiforms and Siluriforms were the orders that showed the best adaptation to the variations caused by the flood pulse of this system and the limnological attributes (dissolved oxygen, pH, electrical conductivity in water, pH, water transparency and depth) are decisive in the arrangement of the ichthyofauna, but their action is not isolated. On the contrary, they are interdependent together with the river-basin connectivity.