Bancos de macrófitas aquáticas em lago de várzea: alimentação de duas espécies de peixes na região de Manaus, Amazonas, Brasil / Banks of aquatic macrophytes of floodplain lake: sites of alimentation of two species of the fish in the region of Manaus, Amazon, Brazil

Resumo Os lagos de varzea da Amazonia sao colonizados por extensos bancos de macrofitas aquaticas constituindo um dos principais habitats dos peixes. A abundância de macrofitas aquaticas sugere que ocorra uma alta disponibilidade de alimentos para os peixes, tanto autoctones quanto aloctones. A dieta de Synbranchus marmoratus e Cichlasoma amazonarum foi avaliada por meio da analise dos conteudos estomacais de 202 exemplares, utilizando o metodo de frequencia de ocorrencia e o gravimetrico sendo os resultados combinados no indice alimentar (IAi). Nos periodos de cheia e seca, os itens alimentares mais ingeridos pelas especies foram os insetos (Hemiptera e Odonata) e os peixes (pedacos e escamas). Regressoes lineares simples revelaram haver diferencas significativas nos tipos de alimentos ingeridos conforme as classes de comprimento. Para S. marmoratus as diferencas ocorreram entre os periodos de cheia e seca enquanto que C. amazonarum foi  somente na cheia. Os resultados apontam que S. marmoratus e C. amazonarum estao utilizando os bancos de macrofitas aquaticas como local de alimentacao. Abstract The aquatic macrophytes banks in the floodplain lakes of the Amazon river constitute a major environments inhabited by fish. The abundance of aquatics macrophytes suggests that there is a high availability of food, autochthones e alochthones, to fish species. The diet composition of S. marmoratus and C. amazonarum was evaluated by the analysis of stomach contents of 201 specimens, by frequency of occurrence and gravimetric methods. The results of both methods were combined in the food index (IAi). In the high and low water periods, the food items most eaten by S. marmoratus and C. amazonarum were insects (Hemiptera and Odonata) and the fish (muscle and scales). The analysis of variance (one-way ANOVA) shows there are significant differences in the food types according length classes. In S. marmoratus differences occurring between high and low water periods. But to C. amazonarum was different only in high water periods. In conclusion, the aquatic macrophytes banks serve as an important feeding place for S. marmoratus and C. amazonarum in Amazon floodplain lakes.