The survey of the ichthyological fauna in a stretch of the Jacuí and Jacuizinho rivers, RS, allowed the identification of twenty species, and the lambaris ( Astyanax bimaculatusand Astyanax fasciatus ) and the humpback whales ( Hemiancistrus sp ) were the most abundant and uniformly distributed fish in the months of collection, while mussum ( Symbranchus marmoratus ) and O tambicu ( Oligosarchus hepsetus ) were the most rare occurrences
