8215

• UCREFRP Catalog Number: 8215
• Author: U.S. Fish and Wildlife Service.
• Title: Final Environmental Assessment
• USFW Year: 1997.
• USFW - Doc Type: Management and Control of Noonative Fish Species in Floodplain Ponds of the Upper Colorado and Gunnison Rivers.
• Copyright Material: NO

Endangered Species. Food supplies for young life stages of the endangered
fishes, during the critical period when high mortality can occur, are
limited in the main channels of rivers in the Upper Colorado River Basin
(Wydoski and Wick 1996). Zooplankton used for food by newly hatched
endangered fishes are more abundant in backwaters and embayments connected
to the river and most abundant in flooded bottomland habitats (Cooper and
Severn 1994a,b,c,d; Mabey and Schiozawa 1993). However, nonnative fish
species in such habitats prey on and compete with the young life stages of
the endangered fishes.
Osmundson (1986) found that endangered fishes in riverside ponds along the
Colorado River survived and grew well in ponds free of nonnative fishes.
Reclamation of floodplain ponds would remove the potential of predation and
competition by nonnative fish species that occurs to young endangered fishes
in the backwaters and embayments of the rivers. Reclaimed floodplain ponds
would be excellent grow-out facilities for captive-reared endangered fishes
prior to release into the rivers of the Upper Colorado River Basin
(Osmundson and Kaeding 1989).
Surveys of floodplain ponds in the Upper Colorado River for Colorado
squawfish and razorback suckers in the late 1980's wehe negative. Only one
private pond near DeBeque, Colorado contained razorback suckers that were
the offspring of several razorbacks that were stranded after the 100-year
floods of 1983 or 1984 receded. However, surveys will be conducted prior
to chemical treatment to check for endangered fishes with gears such as
electrofishing, trammel nets, and trap nets. Although there is a
possibility that an endangered fish in a floodplain pond could be killed by
the chemical treatment, it is not anticipated that many (perhaps one or two)
endangered fish would be killed through the proposed action. The benefits
to endangered fish recovery are believed to be greater than the remote
possibility of killing one or several endangered fish during chemical
treatment.
Powdered rotenone to be used in chemical treatment of floodplain ponds would
be applied carefully so that drift of the powder is controlled and confined
to the target area. Since rotenone is toxic to terrestrial insects that are
used as food by endangered species such as the Southwestern willow
flycatcher, extra precautions will be taken to prevent treatment of
nontarget areas.
Socio-Economics. Most of the sportfish (e.g., green sunfish and largemouth
bass) occupying these ponds do not reach a size desired by anglers and other
species (e.g., carp, white sucker, fathead minnows) are not sought by
anglers. However, some ponds 3 to 6 pounds are caught each year by some
anglers with some regularity (P. Martinez, 1997, Personal Communication).
Stocking nonnative fish for sport fishing in select ponds would continue
following "Procedures for Stocking Nonnative Fish Species in the Upper
Colorado River Basin" that were developed and signed in a Cooperative
Agreement by the Colorado Division of Wildlife, Utah Division of Wildlife
Resources, Wyoming Game and Fish Department, and the U.S. Fish and Wildlife
Service (Colorado Division of Wildlife et al. 1996). A final Environmental
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