9490

• UCREFRP Catalog Number: 9490
• Author: U.S. Fish and Wildlife Service.
• Title: Final Environmental Assessment for Procedures for Stocking of Nonnative Fish Species in the Upper Colorado River Basin.
• USFW Year: 1996.
• USFW - Doc Type: Grand Junction.
• Copyright Material: NO

maintained by stocking. Because this species is a recent introduction
to the Basin, it was not included in Hawkins and Nesler (1991).
16. Green sunfish: The native distribution of this species is in North
America east of the Continental Divide and west of the Appalachian
Mountains, from the Great Lakes region south to the Gulf of Mexico.
Introduced primarily as prey for other fish. Diet includes other
fishes. Known to eat eggs and larvae of endangered fishes and
considered a competitor. Green sunfish were tied for 5th on the list
of 28 nonnative fish species considered to adversely impact the native
fishes in the Colorado River Basin (Hawkins and Nesler 1991).
17. White crappie: Their native distribution is east central North
America from Minnesota west to the Appalachian Mountains south to the
Gulf Coast and west to Texas. Incidental catches of this species have
occurred in Navajo Reservoir, New Mexico. This species has a greater
tolerance for turbid waters and would likely fare better then black
crappie in mainstem habitats. Diet includes other fishes. White
crappie were ranked 28th on the list of 28 nonnative fish species
considered to adversely impact the native fishes in the Colorado River
Basin (Hawkins and Nesler 1991). There low ranking is related to their
limited distribution in the Basin.
18. Grass carp: Their native range is Asia, primarily China and
Thailand. Have been introduced into the United States as a vegetation
control. Only triploid grass carp are being used in the Upper Basin,
because they lack the ability to reproduce. This allows their numbers
and distribution to be controlled. Habitats include lakes, reservoirs,
ponds, rivers, and irrigation ditches. Not known to prey on other
fishes, but can alter habitats of other fishes by changing vegetation.
This species was not included on the list of 28 nonnative fish species
by Hawkins and Nesler (1991), though considered by many as undesirable
in mainstem rivers.
B. Recreational Fishing
1. Colorado: Anglers fished approximately 8.2 million days in 1991;
~~ each angler fished an average of 12.1 days each (Colorado Division of
Wildlife 1992). Seventy-nine percent of this fishing occurred in
Coldwater lakes and streams. The remaining 21 percent was in cool and
warm waters. In the nine counties of the northwest region of Colorado
(area representing the Upper Basin), anglers fished 955,398 days (23
percent) of the State total. Over 70 percent of this fishing was in
cold water habitats. Fishing for warmwater species (black crappie,
largemouth bass, catfish, etc.) represented about six percent of the
fishing effort. Warmwater fishing in the northwest region accounts for
about 9.5 percent of the total warmwater fishing in Colorado. The
Colorado Division of Wildlife would like to increase warmwater fishing
opportunities in western Colorado.
A survey of warmwater anglers in Delta, Garfield, Mesa, and Montrose
counties concluded that anglers fished most often for catfish (36
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