6029

• UCREFRP Catalog Number: 6029
• Author: Platania, S. P. and K. R. Betsgen.
• Title: Interim Report on the Fishes of the Lower San Juan River, New Mexico, 1987.
• USFW Year: 1988.
• USFW - Doc Type: Santa Fe, NM.
• Copyright Material: NO

San Juan rivers and a small stretch of the mainstem Colorado
River below Cataract Canyon. Impoundments in the Sub-basin are
Navajo Reservoir on the San Juan River in New Mexico and Lake
Powell on the Colorado River in Utah. Of the tributary rivers,
the San Juan is the longest, provides the highest discharge, and
is the southern-most major tributary in the Upper Basin (U.S.
Geological Survey 1985, 1985a).
The Colorado River Basin has the highest percentage (87%) of
endemic primary riverine fishes of any North American river basin
(Miller 1959). A total of 55 forms has been reported from the
Upper Colorado River Basin, of which 13 are native and eight are
endemic (Tyus et al. 1982). Among these native forms, four are
federally listed as endangered and two are federal Notice of
Review as candidates for listing. Those "target" species
receiving the most study are the Colorado squawfish
(Ptvchocheilus lucius), species in the genus Gila (bonytail, G.
elegans, humpback chub, G. cypha, and roundtail chub, G.
robusta), and the razorback sucker (Xvrauchen texanus). Target
species, as defined in this report, are the five species listed
in the preceding sentence. While considerable research has been
conducted over the last decade on some of these fishes in the
Green and Upper Mainstem Colorado sub-basins, little attention
has been given to them or other rare fishes in the San Juan Sub-
basin.
The New Mexico portion of the San Juan Sub-basin consists of
the San Juan, Navajo (not shown on figure), Los Pinos, Animas, La
Plata, and Mancos rivers and Navajo Reservoir (Figure 2).
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