Efeitos da alteração ambiental sobre Bryconops giacopinii (Characidae) em igarapés de terra firme: dieta, fator de condição, parasitismo e reprodução

Abstract

Changes in aquatic environments trigger several effects on organisms, especially for fish. These effects can be observed in changes in the dynamics of resource availability, as well as the occurrence of unusual organisms in the natural environment, which in turn, affect the body state and compromise the fitness of individuals. The present study compared biological and parasitological parameters among populations of Bryconops giacopinii (Fernandez-Yépez, 1950) (Characiforms: Characidae) sampled in intact forest streams belonging to the Adolpho Ducke Forest Reserve and in altered streams by damming caused by the construction of the BR-174 highway. Dietary results showed predominance of allochthonous insects in the samples sampled from the intact forest streams, while the specimens obtained in the altered streams consumed larger proportions of autochthonous foods, with the predominance of detritus. The relative condition factor (Kn) was higher for the populations in intact forest streams. Digenetic parasites and nematodes occurred with much greater frequency and abundance in specimens of altered forest streams. There was a significant, but weak, relationship between parasitic abundance and condition factor in B. giacopinii populations from altered streams by BR-174. The fecundity (absolute and relative) of the females was significantly higher among the specimens, besides the occurrence of a positive and significant relationship between the fecundity and the size of the females only from altered streams. On the other hand, there was no difference in oocyte diameter among populations sampled in both types of environments. However, there is an indication of differences in the type of spawning among the populations of the evaluated environments. These results indicate that the changes caused by damming, had a significant influence on some biological and ecological parameters of the local populations of B. giacopinii, being observed the potential of adaptability of the individuals to the impacts generated in the environment. The observed differences indicate that the negative effects of damming are not homogeneous for the various biological aspects measured in the populations that occupy the altered streams by BR-174 highway.