ALP 3

Contents
As a consequence of Lake Nighthorse becoming a nonnative game fishery, adults, juveniles,
larvae, and embryos of these reservoir fish can be entrained into discharge water and potentially
survive to be introduced into downstream waters. However, with the discharge water passing
through the sleeve valve it is highly unlikely that any fish greater than the diameter of the sleeve
valve holes will pass through alive. Although not intentional, entrainment of live fish through
dam outlet structures and into the receiving river is well documented elsewhere (Cramer and
Oligher 1964, Bentley and Raymond 1969, Beamesderfer and Rieman 1991, Berge et al. 1996,
Coutant and Whitney 2000). Larvae, embryos, and fish smaller in diameter than the diameter of
the sleeve valve holes (0.63 inch) can potentially survive sleeve halve passage. Currently, Lake
Nighthorse is stocked with nonnative salmonid game fish. (trout and salmon) which
require cooler water temperatures to survive and are gerioally nat considered as a significant
threat as are other nonnative game fish species found"in the San Juatt'River Basin.
San Juan River Basin Fish
In 1992, a coalition of federal agencW
American Tribes, and private water d
New Mexico established the San Juan
conserve and recover populations of t
development to proceedit'i oomplianc
the second largest of three sub b4s ns
fish species, the Colbm4o pikeminno
as an endangered species "in 1967,(3,2
endangered series, in 1991(5€r" 5
are alsg'l'tsted 'as bridaneered tlir iiah
s, (ncluding the U & Bureau of Reclamation), Native
eueloprnent organizatltrns, and the state of Colorado and
It�ver Basin Recovery Implementation Program (SJRIP) to
wa endangerod fish species irr -the Basin and to allow water
e with"fcderal atid"te,laws." "The San Juan River Basin is
that coin rise tlieUppei'VOlorado River Basin. The two
w, formatlJ*`%nown as the Colorado Squawfish, was listed
FR 400 1) arid, the razorback sucker was listed as an
495'7). The Cdlt)rado pikeminnow and razorback sucker,
out the ettt4re Colorado River Basin (San Juan River Basin
nal Program 1ocument 2010).
A total 6f8"native and 23 nonnative fish species are found in the San Juan River Basin. Fish
surveys during the early 1900's documented the following native species: Colorado River
cutthroat trout (0 clarki pleuri� us), Colorado pikeminnow, roundtail chub, speckled dace, ill
mottled sculpin, fldhnelmout bI(iehead, and razorback sucker. Skeletal remains of bonytail
chub (G. elegans) , list4as enngered in 1980, were also found in the Basin but their historical
presence is inconclusive I "addition to the two (Colorado pikeminnow and razorback sucker
and possibly 3 if the bonytail chub was indeed present in the San Juan River) federally listed
endangered fish, the roundtail chub is listed as endangered by the state of New Mexico and is a
species of special concern by the state of Colorado along with flannelmouth and bluehead
sucker. Colorado River cutthroat trout and roundtail chub are listed as sensitive species in the
state of Utah (SJRIP Final Program Document 2010).
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