Tometes is a genus of pacus in the family Serrasalmidae, the same family as the piranhas, but built for grazing rather than predation. The atlas covers 7 species found across the Amazon and Guiana Shield drainages of Brazil, Colombia, Venezuela, Guyana, Suriname, and French Guiana. They are rheophilic fish, specialists in fast, well-oxygenated rapids and rocky river stretches, where their close-set, incisor-like teeth are used to scrape algae, biofilm, and plant material off submerged rocks rather than to bite flesh. Several Tometes species have only been formally described within the last two decades, as taxonomists worked through what had long been treated as a single widespread pacu.
These are large fish for a home aquarium — the atlas records adult sizes from about 14 in up to over 35.5 in — so Tometes is mostly of interest to public aquaria, pond keepers in the tropics, and as a food and sport fish across its native range, rather than a typical community-tank species, though the Red and black sailfin pacu (Tometes siderocarajensis) is occasionally seen in the specialist trade. Because the genus is tied so closely to fast-flowing rapids habitat, several species are vulnerable to the hydroelectric dam projects that fragment and drown rapids across the Amazon basin, and the atlas records a Vulnerable assessment alongside a mix of Least Concern and not-yet-evaluated species.