Feeding ecology and morphometry of the digestive tract of Astronotus ocellatus (Cichlidae) in várzea environments of the Middle Solimões Region, Central Amazon, Brazil

The diet of Astronotus ocellatus (Osteichthyes, Cichlidae) and the morphometry of its digestive tract were investigated at Mamiraua Sustainable Development Reserve (MSDR), Amazonas, Brazil, between February 2005 and January 2006. A total of 223 specimens were captured and from each of them the total and standard length, length of intestine, and length of abdominal cavity were determined. The intestinal coefficient and the celomatic coefficient were calculated. Contents from stomachs and intestines were analyzed in 182 specimens. Data gathered show A. ocellatus as a carnivorous species, and insects and fish proved to be the most important food items in its diet. It was detected a significant difference in the composition of diets between intestinal and stomach contents, suggesting the importance of separate analysis to better describe the use of food resources available for the fish species in this particular environment. During the year of study the diversity index of the diet was higher in the low water period.