A proper English name seems not to exist. Mostly this fish is referred to by its scientific name, often also as "piapara" (Brazilian form) and "boga" (Argentinian form):

http://www.fishingargentina.com/excursioncrucero.html:
"We will also find the giant Surubi (Pseudoplatystoma coruscans), the Tararira (Hoplias malabaricus), the Pacú (Colossoma mitrei), the Boga (Leporinus obtusidens), the Pira-Pita (Brycon orbygnianus) and the Chafalote (Raphidion vulpinus)."

http://www.si.fcen.uba.ar/fcen/biology/penchaszadeh.htm:
"Predation on the invasive freshwater mussel Limnoperna fortunei (Dunker, 1857) (Mytilidae) by the fish Leporinus obtusidens Valenciennes, 1846 (Anostomidae) in the Río de La Plata, Argentine".

http://www.fao.org/docrep/W7560E/W7560E06.htm:
Piapara | Leporinus obtusidens 2
Piava-bicuda | Leporinus conirostris 1

http://www.brazilspecialist.com/packages/fishinginiguassu/:
"That’s where we find the famous “dourado” (Salminus maxillosus), the prefered fish of sport fishermen, as the “surubim” (Pseudoplatystoma fasciatum fasciatum) and the “pintado” (Pseudoplatystoma corruscans) that reach up to 60 kg. Other smaller fishes are “piapara” (Leporinus obtusidens) and “bagre” (Pimelodus clarias maculatus)."


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Note added at 9 days (2004-04-17 18:00:22 GMT)
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If you are in need of some more references also look into:

http://www.fishbase.org/identification/specieslist.cfm?famco...
Leporinus obtusidens
[] (with photo!)

http://www.scielo.br/scielo.php?script=sci_abstract&pid=S010...
Vitamin C supplementation of piauçu (Leporinus obtusidens)

http://www.biozentrum.uni-wuerzburg.de/bericht/pc1/public_en...
Molecular cytogenetics, organization, and evolutionary conservation of a chromosome specific satellite DNA from Leporinus obtusidens.

http://www.way.com.ar/~invasion/English/AmbNat.htm:
Another kind of impact is observed at Guaíba lake (Brazil), where the golden mussel prevents the normal development of marsh plants like rushes.
The presence of the golden mussel also alters the trophic chains of the environment. For instance, the \"boga\" (Leporinus obtusidens) in the Río de la Plata changed its diet opting for the golden mussel as its main food.

http://www.wes.army.mil/el/ansrp/limnoperna_fortunei.htm:
Predation by the fish Leporinus obtusidens may assist in decreasing the densities of golden mussel populations

Also see why it\'s good to stick to the scientific name:
http://filaman.uni-kiel.de/LarvalBase/ComNames/CommonNameSea...
23 Record(s) for Common Name Boga
Common Name Country Species
Boga Angola Boops boops
Boga Argentina Leporinus elongatus
Boga Argentina Leporinus obtusidens
Boga Azores Islands Boops boops
Boga Bermuda Inermia vittata
Boga Cape Verde Sarpa salpa
Boga Cuba Haemulon striatum
Boga Cuba Inermia vittata
Boga Finland Boops boops
Boga Finland Sarpa salpa
Boga France Inermia vittata
Boga India Labeo boga
Boga Italy Boops boops
Boga Jamaica Inermia vittata
Boga Madeira Islands Boops boops
Boga Peru Orestias cuvieri
Boga Portugal Boops boops
Boga Portugal Chondrostoma polylepis
Boga Spain Boops boops
Boga Spain Chondrostoma polylepis
Boga Spain Inermia vittata
Boga United Kingdom Inermia vittata
Boga USA (contiguous states) Inermia vittata

http://www.gefweb.org/wprogram/Jan99/undp/Required.doc:
In the upper Rio de la Plata, populations of migratory fish -- sábalo (Prochilodus lineatus), boga (Leporinus obtusidens), patí (Luciopimelodus pati) and dorado (Salminus maxillosus) – swim up river, along the lower and middle Parana river at the beginning of autumn and return in the spring.

BTW: There was not one reference with \"Leporinus obtusidens\" and \"bogue\"

Never forget to grade your questions!