Algunos aspectos estructurales y ecológicos de la ictiofauna del Sistema de Iberá (Corrientes, Argentina)

The present paper deals with the structure, distribution and main ecological characteristics of the fish fauna in the wide complex of lenitic water bodies within the Iberá system, at Corrientes Province, Argentina. In the waters of such basin -which covers nearly 1,200,000 ha- were recorded 81 species of fishes, of 59 genera, 19 families and 8 orders. The basic structure of the fish fauna was given by sedentary species (it is: species able to thrive and reproduce in lenitic waters) that are exclusive in the northern area of the system, while only two typical migratory fishes: Prochilodus platensis and Salminus maxillosus, were present at the Southern area (more under the influence of the Corrientes River). The fish productivity is very poor from the economical point of view, particularly at the northern area, being in the higher trophic level fishes of low value, such as Hoplias malabaricus and Hoplerythrinus unitaeniatus (“tarariras”), Acestrorhamphus jenynsi and Acestrorhynchus falcatus (“dientudos”), and more frequently Serrasalmus nattereri and S. spilopleura ("pirañas”). This particular situation is due to the actual high concentration of organic matter derived from the exuberant aquatic vegetation. It is possible that the Iberá system had played in the past, in an environment of large open pools, a very important role in the fish productivity of the regional waters.The present paper deals with the structure, distribution and main ecological characteristics of the fish fauna in the wide complex of lenitic water bodies within the Iberá system, at Corrientes Province, Argentina. In the waters of such basin -which covers nearly 1,200,000 ha- were recorded 81 species of fishes, of 59 genera, 19 families and 8 orders. The basic structure of the fish fauna was given by sedentary species (it is: species able to thrive and reproduce in lenitic waters) that are exclusive in the northern area of the system, while only two typical migratory fishes: Prochilodus platensis and Salminus maxillosus, were present at the Southern area (more under the influence of the Corrientes River). The fish productivity is very poor from the economical point of view, particularly at the northern area, being in the higher trophic level fishes of low value, such as Hoplias malabaricus and Hoplerythrinus unitaeniatus (“tarariras”), Acestrorhamphus jenynsi and Acestrorhynchus falcatus (“dientudos”), and more frequently Serrasalmus nattereri and S. spilopleura ("pirañas”). This particular situation is due to the actual high concentration of organic matter derived from the exuberant aquatic vegetation. It is possible that the Iberá system had played in the past, in an environment of large open pools, a very important role in the fish productivity of the regional waters