Feeding of Cichla monoculus Spix, 1829 (Teleostei: Cichlidae) during and after reservoir formation in the Tocantins River, Central Brazil

NOVAES, J.L.C¹; CARAMASCHI, É.P.¹ & WINEMILLER, K.O.²

¹ Departamento de Ecologia/Instituto de Biologia/ Universidade Federal do Rio de Janeiro Caixa postal 68020 Ilha do Fundão CEP 20 941-970 Rio de Janeiro RJ, Brasil. e-mails: josenovaes@hotmail.com; erica@biologia.ufjr.br

² Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, TX 77843-2258, USA. E-mail: k-winemiller@tamu.edu

ABSTRACT: We examined Cichla monoculus feeding in a stretch of the upper Tocantins River during construction of the Serra da Mesa power plant. Fishes were sampled bimonthly during two periods: reservoir filling (Dec/96 toApr/98) and operation (Jun/98 to Feb/00). Stomach contents analysis confirmed the piscivorous habit of the species but also revealed differences in diet composition between filling and operation phases. Tetragonopterin fishes were the main prey during the filling phase, and cichlids were dominant prey during the operation phase. Reduced feeding was observed in reproductive individuals. Juveniles had a more diversified diet than strongly piscivorous adults. The predator-prey size relationship was weak in both the phases (r² < 0.43) and positive only during the operation phase. We recorded cannibalism on juveniles throughout whole period of study. Feeding plasticity and availability of cichlid prey are probably important factors that explain persistence of C. monoculus in reservoirs.

Key-words: Cichla monoculus, feeding, reservoir, Serra da Mesa.