Ecology and ontogeny of feeding habit of Astyanax janeiroensis (Osteichthyes, Characidae) from a coastal stream from Southeast Brazil

Abstract

In the present work we aimed to describe the spatio-temporal and ontogenetic variations of Astyanax janeiroensis diet in Ubatiba stream, a coastal fluvial system from Serra do Mar. We analyzed 540 specimens collected monthly during twelve months in six sites differing in the degree of vegetal cover (opened and closed sites). We verified that A. janeiroensis is an omnivorous species whose diet is largely based on autochthonous items. The estimated intestinal coefficient was 0.74 (+ 1.2), being compatible with an omnivorous behavior. We did not register differences in the diet from dry and rainy seasons. Nonetheless, we found differences in the diet from opened and closed sites. We registered quite absolute predominance of autochthonous items in the diet from the closed sites, whereas, in the opened ones we found similar ingestion of alo and autochthonous items. Concerning juveniles and adult specimens, we found differences in the consumption of animal and vegetal items with a relative reduction of animal ingestion among adult specimens. The intestinal coefficient of adult specimens was higher than that of juveniles, corroborating the diet results.