vi at ilis . ▁This ▁finding ▁was ▁re iter ated ▁by ▁Cab all ero ▁and ▁colle agues ▁with ▁a ▁larger ▁number ▁of ▁gen es . ▁The ▁existence ▁of ▁two ▁species ▁has ▁been ▁generally ▁accepted ▁by ▁the ▁scientific ▁community . ▁ ▁Distribution ▁The ▁t uc ux i ▁exists ▁along ▁much ▁the ▁length ▁of ▁the ▁Amazon ▁River ▁and ▁many ▁of ▁its ▁trib ut aries , ▁and ▁is ▁found ▁in ▁Venezuela , ▁Brazil , ▁Peru , ▁E cuador , ▁sout he astern ▁Colombia . ▁N umer ous ▁individuals ▁have ▁been ▁seen ▁in ▁the ▁Or in oco ▁River ▁further ▁north , ▁though ▁it ▁is ▁not ▁clear ▁whether ▁these ▁are ▁t uc ux i ▁or ▁cost ero . This ▁species ▁occurs ▁in ▁fresh water ▁habit ats ▁only . ▁ ▁Food ▁and ▁For aging ▁ ▁T uc ux is ▁for age ▁in ▁tight ▁groups , ▁often ▁ch asing ▁fish ▁in ▁rapid ▁dash es ▁just ▁below ▁the ▁water ▁surface , ▁with ▁fish ▁jump ing ▁out ▁of ▁their ▁way . ▁Th irty ▁species ▁of ▁fish ▁are ▁known ▁to ▁be ▁pre y , ▁some ▁living ▁in ▁protected ▁la kes ▁and ▁channels , ▁while ▁others ▁occur ▁in ▁fast - flow ing ▁rivers . ▁ ▁Be hav iour ▁The ▁t uc ux i ▁exists ▁in ▁small ▁groups ▁of ▁about ▁ 1 0 - 1 5 ▁individuals , ▁and ▁sw im ▁in ▁tight - kn it ▁groups , ▁suggesting ▁a ▁highly ▁developed ▁social ▁structure . ▁T uc ux is ▁are ▁quite ▁active ▁and ▁may ▁jump ▁clear ▁of ▁the ▁water ▁( a ▁behavior ▁known ▁as ▁bre