species . ▁ ▁Range ▁In ▁the ▁past , ▁this ▁sub species ▁was ▁found ▁throughout ▁port ions ▁of ▁the ▁Colorado ▁River ▁d rain age ▁in ▁Wy oming , ▁Colorado , ▁Ut ah , ▁Arizona , ▁and ▁New ▁Mexico . ▁However , ▁today ▁scient ists ▁believe ▁this ▁fish ▁occup ies ▁ 1 3 % ▁of ▁its ▁historic ▁range ▁( Range - W ide ▁Status ▁of ▁Colorado ▁River ▁C ut th ro at ▁Tr out ▁( On cor h yn chus ▁cl ark ii ▁ple ur it icus ): ▁ 2 0 0 5 ). ▁ ▁Colorado ▁River ▁cut th ro ats ▁are ▁thought ▁to ▁have ▁occupied ▁the ▁bas in ▁of ▁upper ▁M ud dy ▁Creek , ▁a ▁trib ut ary ▁of ▁the ▁Little ▁S nake ▁River ▁( which ▁ultimately ▁flows ▁into ▁the ▁Colorado ▁River ) ▁in ▁southern ▁Car bon ▁County , ▁Wy oming . ▁Historical ▁accounts ▁in ▁letters ▁and ▁di aries ▁refer ▁to ▁them ▁as ▁" mount ain ▁tr out " ▁or ▁" spe ck led ▁tr out ." ▁The ▁fish ▁may ▁have ▁begun ▁to ▁disappear ▁from ▁the ▁upper ▁M ud dy ▁Creek ▁in ▁the ▁ 1 8 5 0 s ▁as ▁a ▁result ▁of ▁physical ▁changes ▁made ▁to ▁the ▁environment ▁by ▁travel ers , ▁the ▁introduction ▁of ▁the ▁bro ok ▁tr out ▁and ▁other ▁non - native ▁species , ▁and ▁possibly ▁the ▁over - tra pping ▁of ▁be a vers , ▁which ▁affected ▁d ams ▁and ▁dependent ▁habit ats . ▁▁ ▁A ▁distinct ▁line age ▁of ▁Colorado ▁River ▁cut th ro at ▁tr out