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

increase survival in the critical early life stages of the endangered
fishes. Zooplankton densities must be adequate to realize survival of
larval endangered fishes based on studies of razorback suckers by Papoulias
and Minckley (1990). At the same time, nonnative fishes would not be given
the opportunity to multiply in the floodplain ponds since they would enter
the river as the high spring streamflows subside. Earlier in this
Environmental Assessment, it was stated that the target nonnative fish
species for control in floodplain ponds are centrachids, primarily
largemouth bass and green sunfish (Martinez and Nesler 1996). Centrarchid
species do not fare well in the riverine environment based on monitoring of
fish populations by the Recovery Program (McAda et al. 1994 a,b; 1995).
This alternative would be applicable to either natural floodplain
depressions or gravel-pit ponds in the floodplains of the Colorado and --
Gunnison rivers that connect with the river on a frequent basis. Mitchell
(1995) stated that about 60% of the floodplain ponds, included in his -__
inventory, connected with the rivers either annually or one out of ten
years. Reconnection of these ponds with the rivers would allow the
productive off-channel habitats to connect with the rivers annually,
producing zooplankton that are needed by the early life stages of the
endangered fishes.
Burdick (1994} developed a conceptual management plan to experimentally test
the assumptions that were described in the above paragraphs. In the Fall
of 1996, a gravel-pit pond (29 5/8 Road pond) along the Colorado-River near
Grand Junction was re-connected with the river. The fish populations using
this manmade "embayment" are currently being monitored by the Colorado River
Fishery Project of the U.S. Fish and Wildlife Service in Grand Junction,
Colorado. This experimental study will provide insight into the use by
native fishes, including endangered fishes, and nonnative fishes. The
results of this experimental field study will be used for decisions on re-
connecting other floodplain ponds with the river and how to best manage such
manmade "embayments" in the future.
Obviously, this alternative has potential for endangered fish recovery in
some of the floodplain ponds but not all. Therefore, it would be premature
to re-connect a large number of ponds with the rivers until the response of
both native and nonnative fishes is better understood.
Because of the limited floodplain area along the Colorado and Gunnison
rivers, gravel-pit ponds will be reconnected with the rivers under the
Recovery Program element involving habitat rehabilitation and restoration.
The number of ponds that will be involved under the habitat element depends
upon success in gaining access through willing landowners. Ponds under
private ownership on the Colorado River constitute about 73% of the total
number and about 44% on the Gunnison River (Mitchell 1995). Therefore, this
alternative by itself cannot achieve the level required by the Recovery
Program to control chronic escapement of nonnative fishes.
No impacts are expected on land use, Indian trust assets, or environmental
justice under this alternative.
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