Dinâmica populacional e alimentação de crenuchus spilurus günther, 1863 em igarapés da bacia amazônica

Abstract

Studies on the utilization of food resources provide important information on the ecology of species, constituting a tool for obtaining trophic data from ecosystems and variations resulting from anthropogenic disturbances. Thus, the aim of this study was to verify the population dynamics and analyze the feeding ecology of C. spílurus in streams of the Amazon basin. The specimens were collected in four localities: Coari-AM, Benevides-PA, Juruti-PA and Caxiuanã National Forest (Melgaço and Portel-PA). After the collections, the individuals had their total weight (g) and standard length (mm) measured. In the laboratory, stomachs and gonads were analyzed, obtaining the following results: in Benevides, Exoskeleton fragments composed 13.29 of the food importance (iAi%), Diptera (Chironomidae) composed 1.07 of the IAi%, followed by 0.10 for Diptera (Culicidae) and Trichoptera (Polycentropodidae) and 0.05 for Acari; in Coari, the food importance (lAi%) registered 21.40 of Exoskeleton fragments and 11.09 of Diptera (Chironomidae): Luruti specimens, showed lAi% of 38.39 for exoskeleton fragments and 30.31 for Crustacea. While individuals from Caxiuanã recorded IAi% of 25.0 for exoskeleton fragments, 0.15 for Crustacea and 0.1 O for Trichoptera. These results are similar to studies carried out with other individuals of the Crenuchidae family, where the predominance both in occurrence and abundance was of the same Chironomidae family. Regarding sex ratio, individuals from Coari presented male/female ratio (1:1) (a = 0.227, G.L.= 1 and p > 0.63); Benevides presented (2:1) (a = 4.5, G.L. = 1 and p < 0.05); Juruti, (6.5:1) (a = 16.133,0 G.L.= 1 and p < 0.05) and Caxiuanã, although the sex ratio observed was (2:1), this was not significantly different (a = 3.33, G.L.= 1 and p = 0.067). Based on these results the population composition does not present a similar pattern for these localities in Amazonia.