Importance of zooplankton in the diet of a small fish in lagoons of the
upper Paraná River floodplain, Brazil
RUSSO1, M.R. & HAHN2, N.S.
1 Programa de Pós-graduação e 2 Universidade Estadual de Maringá – Núcleo de Pesquisa em Limnologia, Ictiologia e Aqüicultura (Nupelia)/ Programa de Pós-graduação em Ecologia de Ambientes Aquáticos Continentais, Av. Colombo, 5790, Bl. G-90, 87020-900, Maringá, Paraná, Brasil.
e-mail: ecorusso@yahoo.com.br, hahnns@nupelia.uem.br
ABSTRACT: Spatial and seasonal variations in the diet of Aphyocharax anisitsi (Eigenmann & Kennedy, 1903) were analysed between 2000 and 2001 in three isolated lagoons (Genipapo, Jacaré and Traíra) of the upper Paraná River floodplain. Simple seinings were performed along the marginal areas of the lagoons during the day. Analysis of 136 stomach contents was done by the volumetric method and the species was classified as predominantly zooplanktivore. Aphyocharax anisitsi feeds mainly on microcrustaceans (Cladocera and Copepoda), in addition to Decapoda larvae, insect larvae and detritus. Diet composition showed significant differences between hydrological periods and lagoons. Food resources consumed in the Genipapo lagoon during the dry period were different from those consumed in the Genipapo and Jacaré lagoons during the rainy period, and in the Traíra lagoon in the dry period. Calanoida was more consumed in the rainy period and insect larvae were consumed in the dry period. The availability of microcrustaceans did not influence the diet because the species selected most of its food resources. The ability of A. anisitsi to predate upon zooplankton suggests that this species can be an important trophic link between primary producers and top levels of the food web in the isolated lagoons of the upper Paraná River floodplain.
Key-words: Aphyocharax anisitsi, planktivory, selectivity, freshwater, floodplain.