Biological and ecological characteristics of Roestes molossus (Teleostei: Cynodontidae), a night hunting characiform fish from upper Madeira River, Brazil

Abstract

During fish samplings carried out between 2004 and 2005 in tributaries draining the rapids stretch of Madeira River in Brazilian Amazon, we captured 72 specimens of Roestes molossus, a rare and poorly known cynodontid species. These specimens comprised 1.17 % of the total catches with gillnets (out of 175 species), the smallest measuring 114 mm SL and the largest 198 mm SL. Males were smaller than females, which predominated in the higher length classes. Sex-ratio was roughly 1:1, and ripe females occurred in December, during the rising water period. Roestes molossus fed on small fishes, insects and shrimps, which live associated to submerged litter banks. The tributaries of the Madeira River rapids zone are important habitats in the life cycle of K. molossus. However, the absence of small-sized specimens in our samples indicates that the first development phases occur in other places or microhabitats not sampled in our study. © 2008 by Verlag Dr. Friedrich Pfeil, München, Germany.