8231

• UCREFRP Catalog Number: 8231
• Author: Maddux, H. R.
• Title: Draft Environmental Assessment For Procedures For Stocking Of Nonnative Fish Species In The Upper Colorado River Basin.
• USFW Year: 1996.
• USFW - Doc Type: Grand Junction, CO.
• Copyright Material: NO

located the pond above the floodplain. No private ponds used for
warmwater fishing are known to occur in the portion of Wyoming covered
by these procedures. The only floodplain pond is near the Town of Baggs
along the Little Snake River and is stocked with trout provided by the
Wyoming Game and Fish Department.
V. IMPACT ASSESSMENT/ENVIRONMENTAL CONSEQUENCES
While physical habitat parameters have an influence on the ability of a
species to compete against other species, the evolutionary history of
both species also plays an important role. Species that evolved ti in
river basins supporting large numbers of species are usually more
aggressive and successful competitors than species from depauperate
basins. As discussed previously, the Colorado River Basin fish fauna is
a depauperate one and competition was limited. Most of the introduced
nonnative fish species are from basins with larger and more varied fish
faunas, and evolved in very competitive environments.
Nonnative fish may physically compete for space and food with native
species. Other adverse effects include direct predation, harassment or
the introduction of diseases or parasites. Predation. especially on
egg. larval and juvenile stages, is a significant factor in determining
population survival through the effects to recruitment. Research has
shown that nonnative fish play an important role in suppressing native
fish recruitment. Spawning adults of the four Colorado River endangered
fish can be found during the breeding seasons. Actual spawning has been
documented for all species and larvae have also been found. Yet
recruitment of juveniles into these populations is very low.
Tyus and Saunders (1996) summarized scientific studies in the Colorado
River Basin that documented predation as follows: "Direct proof of
predation by nonnative fishes on the native species in the Colorado
River basin included reports by Jonez and Sumner (razorback sucker eggs
eaten by common carp: 1954); Coon (Colorado squawfish eaten by channel
catfish; 1965), Taba (Colorado squawfish and chubs eaten by bullheads;
1964), Meffe (Sonoran topminnow eaten by mosquitofish: 1985); Langhorst
and Marsh (razorback sucker eaten by green sunfish; 1986), Hendrickson
and Brooks (Colorado squawfish eaten by smallmouth bass and bullheads:
1987), Osmundson (Colorado squawfish eaten by largemouth bass, green
sunfish. black crappie, and black bullhead; 1987), Marsh and Brooks
(razorback sucker eaten by channel and flathead catfishes; 1993);
Ruppert et al. bluehead sucker eaten by red shiner; 1993); Crowl and
Lentsch (Colorado squawfish eaten by northern pike; 1995), Mueller
(razorback sucker eaten by sunfishes and largemouth bass; 1995). Muth
and Beyers (Colorado squawfish and razorback sucker larvae eaten by
channel -catfish and green sunfish: in press). Nesler (roundtail chub,
speckled dace, bluehead and flannelmouth suckers eaten by northern pike;
1995), and Valdez and Ryel (humpback chub eaten by brown and rainbow
trouts and channel catfish; 1995). Razorback sucker eggs and larvae are
eaten by channel catfish, green sunfish and carp (Medel-Ulmer 1983,
Minckiey 1983, Langhorst 1987, Marsh and Langhorst 1988)."
26