8017

• UCREFRP Catalog Number: 8017
• Author: U.S. Department of the Interior, B. o. R.
• Title: Finding of No Significant Impact, Management and Control of Nonnative Fish Species in Floodplain Ponds along the Upper Colorado and Gunnison Rivers.
• USFW Year: 1998.
• USFW - Doc Type: Denver, CO.
• Copyright Material: NO

undoubtedly contributed to the demise of the endangered Colorado
River fishes.

Nonnative fishes compose 76% of the fish species (42 of 55 species)
in the riverine environment of the Upper Colorado River Basin (Tyus
et al. 1982). These nonnative fishes constitute most of the fish
numbers (96.7 - 99.6%) found in backwater habitats in the Upper
Basin (Cranney 1994; McAda et al. 1994a.b; 1995). Researchers and
other participants in the Recovery Program agree that predation and
competition by established. self-sustaining populations of
nonnative fishes and chronic escapement of nonnative fishes from
off-channel ponds and impoundments are factors that increase
mo rta 1 i ty of the endangered fi shes. They fu rthe r agreed that
action to control nonnative fishes was needed immediately.

Recovery Program participants identified an urgent need to control
or manage nonnative fish species in the Upper Colorado River Basin
if recovery of the endangered fi shes was to be achi eved. They
participated in the development of a strategic plan to remove or
reduce existing populations of nonnative fish species from habitat
used by the endangered Colorado River fishes (Tyus and Saunders
1996). One of the highest priorities in the Recovery Program's
strategic plan for control of nonnative fishes is prevention of
chronic escapement of nonnative fish species from off-channel ponds
along the Upper Colorado and Gunnison rivers that could further
exacerbate existing interactions of nonnative fishes (i.e..
predation and competition) on the endangered fishes.

Recovery Program participants believe it is unlikely that the
endangered fishes will be recovered (i.e.. establish viable. self-
sustaining populations through natural reproduction) until problems
associated with nonnative fishes are addressed.

The proposed action was to use mechanical fish control methods of
draining floodplain ponds and removing nonnative fish species or to
treat the ponds with powdered rotenone that is an excellent
pi sci ci de. The nonnati ve fi shes woul d be removed from
approximately 25 ponds annually and up to 150 ponds by the Year
2002.

The proposed action will decrease the chronic or periodic
escapement of nonnative fish species from floodplain ponds and

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