Reproductive biology and feeding habits of Hemigrammus bleheri (Characiformes: characidae) an ornamental fish the middle Negro River Basin, Amazonas State, Brazil

Abstract

The aim of this study is to describe the reproductive biology, diet and the feeding activity of Hemigrammus bleheri from middle Rio Negro, State of Amazonas-Brazil, along the a hydrological cycle. For this, the gonadal maturation stage, size of first sexual maturation (L₅₀), fecundity and reproductive period of 260 individuals were analyzed, as well the stomach contents of 177 individuals were analyzed and their stomach fullness index calculated. The results indicate that this species has multiple spawning, with oocytes varying between 0.06 and 0.66 mm in diameter and fecundity, between 101 and 721 oocytes. The first sexual maturation size (L₅₀) was estimated at 2.8 cm for females and 2.6 cm for males. Females mature with the flood pulse (December to May) and spawning occur in greater proportion at the end of the flood (March to May). The species is omnivorous, consuming a large part of the food of autochthonous origin. The basic diet showed seasonal variations in its composition, because it was observed that microcrustaceans have their increased importance in flooding/flood periods, and filamentous algae, chironomids and vegetal fragments are more frequent in the drying/dry season. In addition, seasonal changes in food activity were also recorded, probably influenced by the flood pulse, as the degree of stomach repletion was higher in flooding/flood and lower in drying/dry.