Daily variation feeding of Astyanax lacustris (Lütken 1875) in a subtropical river

Abstract

This study aimed to know the daily variation of Astyanax lacustris (Lütken 1875) feeding in a lotic environment. Fish were caught with a net for three days every three hours in the summer to capture ten individuals per hour in a stretch of the Ijuí River, Middle Uruguay River, Brazil. The captured specimens had their stomachs removed and the content analyzed and separated into seven food categories with the aid of stereomicroscope. For the analysis of food items were used the frequency of occurrence methods, volumetric method and applied the Alimentary Index (IAi). Two hundred stomachs were analyzed, of which 95% had food content. The most abundant items were algae and autochthonous insects. Astyanax lacustris feeds throughout the day especially early in the morning (9 hours) and reduces its feeding at night (24 hours and 3 hours). It was also verified variation of AI of different food items throughout the day. It is concluded that A. lacustris feeds throughout the day, especially in the daytime and that throughout the 24 hours it varies its diet due to photoperiod and food availability.

Food resource partitioning among sympatric populations of five species of freshwater fish (Characidae) in southern Brazil.

“…The present work describes and analyzes the diet of five sympatric characid species from the upper section of a river in southern Brazil, aiming to identify possible interspecific and ontogenetic differences that explain their coexistence. The studied characid species have been reported as omnivores with trophic plasticity, such as Astyanax lacustris (Lütken 1875) (Bastian et al 2021) 2011). Diet overlap among these five sympatric characid species is still unknown for the studied region.…”