Effects of flood regime on the diet of Triportheus curtus (Garman, 1890) in an Amazonian floodplain lake

Abstract

We analyzed the diet of Triportheus curtus in Lake Amapá on the Acre River (AC - Brazil), during three distinct phases of the hydrological cycle (pre-flooding, flooding, and post-flooding stages). The flooding occurred between January and June of 2009. Samples were collected monthly from October 2008 through September 2009. After collection (at 19:00, 01:00, 07:00, and 13:00 hs) and taxonomic identification, fish were eviscerated and their stomachs preserved in a 4% formalin solution for later analysis. The diet was evaluated by the Index of Relative Importance (IRI), and temporal variations (pre-flooding, flooding, and post-flooding) in the diet were summarized by an ordination technique (DCA). The diet of T. curtus was comprised of several orders of insects and microcrustaceans. In the pre-flooding stage, more than 62% of the diet consisted of Ostracoda. In the flooding phase, T. curtus fed mainly on Chaoboridae larvae (Diptera) (44.3%) and terrestrial insects (fragments) (33.7%). In the post-flooding phase, Chaoboridae comprised 80% of the diet. These results indicate that the utilization of food resources by T. curtus was variable, changing with alterations in the availability of resources, as influenced by the hydrological cycle. The population of T. curtus proved to be opportunistic, changing its diet in the course of the hydrological cycle.