GENERAL31841

• Permit No: M1999002
• IBM Index Class Name: General Documents
• Doc Date: 7/22/1999
• Doc Name: FINAL ENVIRONMENTAL IMPACT STATEMENT VOLUME 2 APPENDIX L
• Media Type: D
• Archive: No

5
50 CFR 402.02 as a direct or indirect alteration that appreciably
diminishes the value of critical habitat for both the survival and
recovery of a listed species. In considering the biological basis for
designating critical habitat, the Service focused on the primary
physical and biological elements that are essential to the
conservation of the species without consideration of land or water
ownership or management. The Service has identified water, physical
habitat, and biological environment as the primary constituent
elements. This includes a quantity of water of sufficient quality
that is delivered to a specific location in accordance with a
hydrologic regime that is required for the particular life stage for
each species. Water depletions reduce the ability of the river system
to provide the required water quantity and hydrologic regime necessary
for recovery of the fishes. The physical habitat includes areas of
the Colorado River system that are inhabited or potentially habitable
for use in spawning and feeding, as a nursery, or serve as corridors
between these areas. In addition, oxbows, backwaters, and other areas
in the 100-year floodplain, when inundated, provide access to
spawning, nursery, feeding, and rearing habitats.
STATUS OF THE SPECIES AND CRITICAL HABITAT
SppC~ pia ~(`riti al H hi aY D Hi ion
The Colorado pikeminnow is the largest cyprinid fish (minnow family)
native to North America and it evolved as the main predator in the
Colorado River system. It is an elongated pike-like fish that during
predevelopment times, may have grown as large as 6 feet in length and
weighed nearly 100 pounds (Behnke and Benson 1983). Today, fish
rarely exceed 3 feet in length or weigh more than 18 pounds; such fish
are estimated to be 45-55 years old (Osmundson et al. 1997). The
mouth of this species is large and nearly horizontal with long slender
pharyngeal teeth (located in the throat), adapted for grasping and
holding prey. The diet of Colorado pikeminnow longer than 3 or
4 inches consists almost entirely of other fishes (Vanicek and Kramer
1969). Males become sexually mature earlier and at a smaller size
than do females, though all are mature by about age 7 and 500 mm
(20 inches) in length (Vanicek and Kramer 1969, Seethaler 1976, Hamman
1981). Adults are strongly countershaded with a dark, olive back, and
a white belly. Young are silvery and usually have a dark, wedge-
shaped spot at the base of the caudal fin.
Based on early fish collection records, archaeological finds, and
other observations, the Colorado pikeminnow was once found throughout
warmwater reaches of the entire Colorado River Basin down to the Gulf
of California, and including reaches of the Upper Colorado River and
its major tributaries, the Green River and its major tributaries, and
the Gila River system in Arizona (Seethaler 1976). Colorado