Le bas Oyapock limite septentrionale ou simple étape dans la progression de la faune des poissons d'Amazonie occidentale

Abstract

Eight species of Serrasalminae (Teleostei, Characidae) are regularly cited from central Amazonia and from the western part of the Amazonian basin, from southern Bolivia to Colombia. In oriental Amazonia, the area of distribution of this group extends to the várzea, a biotope under the influence of muddy water, and sometimes to the lowest part of the clear water tributaries. This totality is part of a guild of Serrasalminae of várzea. Near the mouth of the Amazon, one observes a gradual impoverishment of the guild along the banks and coastal marshes of the Amapá, until the Oyapock River (frontier stream between Brazil and French Guiana). The Oyapock is also the northern distribution limit of several other western Amazonian species reported in the marshes of Amapá. The marshes of Amapá, situated on very recent sedimentary trainings, are of relatively young age. The different limits of distribution observed along the marshes of Amapá are interpreted as being the many pioneer fronts of the progression of the Amazonian fauna to the north, around the Guianian shield. The Oyapock is interpreted as the most northern front.