Serrasalmidae

Family of fishes

The Serrasalmidae (serrasalmids) are a family of characiform fishes, recently elevated to family status. It includes more than 90 species. The name means "serrated salmon family", which refers to the serrated keel running along the belly of these fish. Fish classified as Serrasalmidae are also known by these common names: pacu, piranha, and silver dollar. These common names generally designate differing dental characteristics and feeding habits. Many species change diets depending on age and resource availability. The remaining primarily herbivorous species can be divided into two groups based on ecology and, to some extent, phylogeny: Colossoma, Mylossoma and Piaractus are mainly found in relatively slow moving waters, and feed extensively on fruits, nuts and seeds, playing an important role as seed dispersers. Mylesinus, Myleus, Ossubtus, Tometes and Utiaritichthys are found in fast flowing sections of rivers, and mainly feed on aquatic plants, especially Podostemaceae.

The Serrasalmidae were recently classified as a subfamily of the Characidae. Their relationship to other characiforms has yet to be determined. The taxonomy and systematics of piranhas and their relatives are complicated and much remains unsettled. Consequently, both species identification and phylogenetic placement of many taxa are problematic. Despite this, the Serrasalmidae are relatively well understood, and agreement is wide on the genera and species included.

The fossil record, particularly for piranhas, is relatively sparse. Most known fossils are from the Miocene, although a few unidentified forms are considered Paleocene and two reportedly date to as early as the Late Cretaceous. All serrasalmine genera had originated by the middle Miocene, with the possible exception of three of the four piranha genera (Pygocentrus, Pristobrycon, and Serrasalmus).

Many serrasalmids are in demand as aquarium ornamentals, and several pacus, such as Piaractus and Colossoma, are economically important to commercial fisheries and aquaculture. Piranhas are generally less valued, although they are commonly consumed by subsistence fishers and frequently sold for food in local markets. A few piranha species occasionally appear in the aquarium trade, and, in recent decades, dried specimens have been marketed as tourist souvenirs. Piranhas occasionally bite and sometimes injure bathers and swimmers, but serious attacks are rare and the threat to humans has been exaggerated. However, piranhas are a considerable nuisance to commercial and sport fishers because they steal bait, mutilate catch, damage nets and other gear, and may bite when handled.