In Brazil, industrial fishing of the piramutaba catfish is performed at the estuary of theAmazon River, utilizing bottom-trawl nets as equipment. This fishing technique is considered potentially the most harmful to the environment and to biodiversity, due to the destruction of biomes and incidental capture of several species, called "bycatch.†In order to characterize the species which compose the ichthyofauna bycatch of the piramutaba catfish, we analyzed 459 fishing trawlers between the years of 2002 and 2008, in the allowed and forbidden areas. The results revealed that the ichthyofauna bycatch of the piramutaba consists of 38 species, divided in 33 genera and 17 families. The piramutaba was confirmed as the main species, consisting of 76% of the overall product, and the gilded catfish as the main bycatch species, consisting of 7.05% of the product. We have recorded the incidence of jewfish (Epinephelus itajara), which can be found in the International Union for Conservation of Nature list of critically endangered species. In despite the production was higher in the rain season than in the dry season, there was no statistical difference in the rate of biodiversity in different areas or periods.