9688

• UCREFRP Catalog Number: 9688
• Author: Upper Colorado River Endangered Fish Recovery Program.
• Title: Nonnative Fish Control Workshop Summary, Conclusions, and Recommendations.
• USFW Year: 2002.
• USFW - Doc Type: Lakewood, CO.
• Copyright Material: NO

non-sport fish (98%) (Figure 2). Of these 75 ponds, 54 were sampled one to four years following
treatment. Follow-up inspection and fish sampling showed that 35 (65%) of these 54 ponds had
been reinvaded by nonnative fish, six (11%) were dry, and 13 (24%) had not been reinvaded by
the date sampled. Twelve ponds (34%) were reinvaded by fathead minnow and 25 (71 %) were
reinvaded by stunted green sunfish (Figure 3). Most ponds that reinvaded fill with irrigation
water or water pumped directly from the rivers. Though seasonal filling and drying of
ponds/wetlands controlled resident nonnative fish, they were easily reinvaded by nonnative fish
from neighboring ponds or through irrigation water.
Additional effort to control invasion or escapement by nonnative fish was attempted by the
installation of nine outlet and two inlet screens that functionally treated 27 ponds. Though none
of the outlet screens have been evaluated, larvae of fathead minnow, roundtail chub, and red
shiner passed through a 0.5-mm wedgewire screen installed on the intake to the threatened and
endangered fish ponds at Horsethief Canyon State Wildlife Area.
An incentive package was developed to provide a monetary incentive to encourage voluntary
participation in the Nonnative Fish Control Program. Door-to-door discussions -and negotiations
were held with landowners which fostered cooperation and facilitated access to privately owned
land. In the sampling phase, contracts were signed with each landowner, and they were paid
$100 per surface acre after sampling: As part of the contract, fish were removed at landowner
discretion. A total of 45 landowners participated from 1997 to 2001. Screening of outlets on
jurisdictional dams required a 10-year commitment by the landowner for maintenance and
operation and athree-way contract between the landowner, vendor, and CROW; screens at other
sites or non jurisdictional dams did not have-these requirements. Eight landowners participated
in screen installation from 1997 to 2001. Ponds were screened through a process of negotiation
with land owners that included landowner input on design and installation. Experimental screens
were strategically installed on two inlet and nine outlet. These screens may control the
movement of nonnative fish in 27 ponds (140 surface acres). Evaluation of both inlet screens is
ongoing. Screening concerns include maintenance and design, dam safety, berm height, and
water velocity and pressure (head).
Methods of controlling nonnative fishes included chemical treatment with rotenone (power &
liquid) and chlorine; water management; black plastic liners; and herbicides. Rotenone was
applied by boat or from the shore. Boat application included dripping rotenone into the water or
it was educted (vacuumed) through pumps and sprayed onto pond surfaces and mixed with the
action of the boat propeller. For shore application, rotenone was educted through a pump from
an agricultural tank and sprayed onto the pond surface. A total of 75 ponds (352 surface acres)
within the study area were treated with one or more of these methods. Anon-toxic dye was
applied to identify leaks or underwater pipes prior to reclamations.
Sampling workshops and Information and Education programs were provided to Project Wild
teachers, and Mesa College and Grand Valley public school (grades 3 through 12) students.
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