Diet composition of fish assemblage of Lake Tupe, Amazonas, Brazil

Abstract

Taxonomic composition and diet composition of a fish assemblage in the lake Tupé during low water season were studied. Lake Tupé is a Central Amazonian blackwater lake in the Rio Negro basin. At high water season, fishes have access to the flooded forest and can freely migrate between the lake and the river Negro, while at low water season these options are not available. Fishes were captured at three dates during low water. Specimens were identified, and for each specimen degree of stomach repletion, content of adipose tissue and stomach content were examined. With the results, fish species were assigned a trophical class. Some species could not be assigned any of these classes and were considered unspecific herbivores, unspecific carnivores or omnivores. The two most abundant species were Acestrorhynchus falcirostris and Hemiodus immaculatus. The most important food item was plant material, and the most abundant trophic class was specialized herbivore. Plant material is generally considered to play a minor role in the diet of Amazonian fishes. This supports the conclusions that during low water, the fish community in the lake Tupé relies heavily on allochtonous input of food. Therefore, and due to the high degree of competition, many fish species perform strong shifts in their feeding habits.