The Guamá River is the main body of water that bathes the city of Belém and is located at the NE limit of the Amazon. It presents a varied physiography along its 380 km course, providing favorable environments for biodiversity. In order to study the ichthyofauna of the region, a plan was made to explore the Guamá and its tributaries. Trawls, puçás, and tarrafas were used for collecting fish. The animals were sorted, fixed in 10% formalin and preserved in 70% alcohol for analysis. Preliminary collections were made during the dry and flood seasons at the same sites, in igarapés of clear water, moderate current and gravel bottom, and lakes of turbid water and sedimentary bottom along the river banks, between the municipalities of Ourém and Capitão Poço. There was a variation in the water level of the river of approximately 4m between one station and another. The order Characiformes comprised about 60% of the species collected. In this group, the Characidae and Curimatidae families showed the greatest diversity, while Anostomidae, Lebiasinidae, Chilodontidae and Erythrinidae showed the least representation. Among the caracids, the Tetragonopterinae were more diverse, with at least three significant genera: Moenkhausia, Hyphessobrycon (dry); and Bryconops (flood). The Curimatidae showed the highest biomass in the dry season, with 67% of the total; in the flood, however, the Characidae predominated with 61.5%. The most populous Curimatidae species were the endemic Cyphocharax gouldingi, and C.spilurus, previously recorded NNW of the region as far as the Guianas. Other stretches of the river will have to be sampled, however, in order to confront information and allow estimation of the ichthyofaunal composition of the region. It is my goal to conclude this work with a functional key for the identification of all species in the region.
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