Feeding of C;chla monoculus Spix, 1829 (Teleostei: Cichlidae) during and after reservoir formation in the Tocantins River, Central Brazil
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چکیده
Feeding of C/chla monoculu. Splx, 1829 (Teleo8tel: Clchlldae) during and after re..rvolr formation In the Tocantln. River, Central Brazil. 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 to Apr/98) and operation (Jun/98 to Feb/OO). Stomach contents analysis confirmed the plsclvorous habit of the species but also revealed differences In diet composition between filling and operation phases. Tetragonopterln fishes were the main prey during the filling phase, and clchllds were dominant prey during the operation phase. Reduced feeding was observed In reproductive Individuals. Juveniles had a more diversified diet than strongly plsclvorous adults. The predator-prey size relationship was weak In both the phases (r' ( 0.43) and positive only during the operation phase. We recorded cannibalism on Juveniles throughout whole period of study. Feeding plasticity and availability of clchlld prey are probably Important factors that explain persistence of C. monoculus In reservoirs. Key-word.. Clchla monoculus, feeding, reservoir, Serra da Mesa. RESUMO: Alimenta~Ao de Clchla monoculus Spix, 1829 (Te'-tel: Clchlidae) durante e 8p6a a forma~Ao de um reservat6rlo no Rio Tocantins, Brasil Central. Neste trabalho caracterlzamos a allmentac;ao de Clchla monoculus em urn trecho do alto ria Tocantlns durante a Instalac;ao da uslna hldreletrlca Serra da Mesa. Os pelxes foram capturados blmestralmente em dais penodos: rase de enchlmento do reservat6rlo (dez/96 a abr/98) e rase de operac;ao da uslna hid relet rica (jun/98 a fey/DO). As anallses do conteudo estomacal conflrmaram 0 hablto plsc{voro da especle. porem revelaram dlferenc;as na composlc;ao da dleta entre a rase de enchlmento e a rase de operac;ao. Carac{deos tetragonoptenneos foram as principals presas na rase de enchlmento e clclldeos foram domlnantes na rase de operac;ao. Fol observada reduc;ao da atlvldade allmentar em Indlv{duos reprodutlvos. Juvenls apre. sentaram dletas dlverslflcadas quando comparadas it forte plsclvorla dog adultos. A relac;ao predador-presa fol fraca em ambas as rases (r' (0.43) e posltlva apenas na rase de operac;ao. Canlballsmo fol reglstrado ao lonso de todo 0 periodo de estudo. A plastlcldade allmentar e disponlbllldade de clclldeos como presas sao. provavelmente. fatores que expllcam a perslstencla de C. monoculus em reservat6rlos. Palavras.ochave: Clchla monoculus. allmentac;ao. reservat6rlo. Serra da Mesa.
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