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Contents
<br />Historically, the bluehead, flannelmouth, and razorback (Xyrauchen texanus) suckers comprised
<br />the medium to large size Catostomid populations in the Upper Colorado River Basin (Ptacek et
<br />al. 2005). Currently, distribution and abundance of bluehead suckers have diminished
<br />(Bezzerides and Bestgen 2002) as well as other native sucker populations within the basin
<br />(Minckley and Deacon 1991). However, bluehead suckers are found in the Colorado, Dolores,
<br />Duchesne, Escalante, Fremont, Green, Gunnison, Price, San Juan, San Rafael, White, Yampa,
<br />and numerous smaller tributaries (Bezzerides and Bestgen 2002). Bluehead sucker populations
<br />exist in several tributary streams immediately downstream of the; an Juan National Forest.
<br />Bluehead suckers are found in the Florida, La Plata, Los PiripsI, acid Animas Rivers (Ptacek et al.
<br />2005) however, recent data suggests the species is
<br />their historic range (Bezzerides and Bestgen 2002)
<br />caused by the alteration of thermal and hydrologic„
<br />interactions with nonnative species (Ptacek et al.
<br />The lower Animas River from Durango, Colorado , c
<br />supports a healthy population of native suckers. Of
<br />between 1997 and 2007 by Valdez (2008), bluehead
<br />fish) and flannelmouth suckers make ,uEp:almpst 21
<br />River fish population. When combined;,,-the trvo p,
<br />percent of the total fish population whereas; nonne
<br />the lower Animas River a- population (Valdez 21
<br />found in only 45 percent of
<br />r this decline are most likely
<br />aliort of habitat, and
<br />the confluence with the San Juan River
<br />he total cats of large - bodied fish sampled
<br />suckerg comprised 37.2 percetrt (15,976
<br />ercerit (9,033 fish) of the lower Animas
<br />ve sucker populations comprise over 58
<br />re : :game fishrnake up almost 36 percent of
<br />Competition for restittrces, predation, parasitism; iWibreeding,. "diseases transmission, and
<br />physical changes to habitat are soin' of the knot effects to native fish communities caused by
<br />introductions of nonnative "fish. ; ay introduced' fish species tend to be well - adapted to a
<br />variety, taferivi tnmental condi"tons allowirig,for a competitive advantage (Ptacek et al. 2005).
<br />All )i£e stages of the "rntduced" vrhite sucker, du( to similar life history traits, have a competitive
<br />impact tan bluehead and', elmouklt =sucker populations. However, the most serious threat
<br />imposed b ,the introduction'of white suitiker (C. commersonii) is through hybridization. These
<br />two species wear to lack any ,Signi scant mechanism to isolate reproductive individuals and
<br />distribution and "alundance of White sucker are increasing within the Upper Colorado River
<br />Basin (Ptacek et dl,, 2005). Otte »hundred and fifty -nine flannelmouth x white sucker hybrids and
<br />fifteen bluehead x White:suck r hybrids were found in fish surveys conducted in the lower
<br />Animas River between f9374nd 2007 (Valdez, 2008).
<br />A total of 17 fish species were captured in the Animas River between Purple Cliffs and the
<br />confluence of the San Juan River (approximately 91 km, 56.5 miles). Six species are native;
<br />bluehead sucker, Colorado pikeminnow (Ptychocheilus lucius), flannelmouth sucker, mottled
<br />sculpin (Coitus bairdi), roundtail chub, and speckled dace (Rhinichthys osculus). Only four
<br />roundtail chub and three Colorado pikeminnow were caught during the 10 years of sampling.
<br />Eleven species are nonnatives that have been introduced into the Animas River over the years.
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