3110

• UCREFRP Catalog Number: 3110
• Author: Sublette, J. E.
• Title: Survey Of The Fishes Of the San Juan River Basin, With Particular Reference To The Endangered Species.
• USFW Year: 1976.
• USFW - Doc Type: Albuquerque, New Mexico.
• Copyright Material: NO

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Thus, warm, turbid waters suitable for native fish are to be found only

in the middle and lower San Juan basin. Unfortunately, this is an area with

high concentrations of two prime competitors - channel catfish and red shiners

(cf Figs. 24, 25, 28 and 29).

Bolden'and Stalnaker (1975) comment:

"Another reason for the decline in endeuiic fish numbers in the

upper basin is competition from introduced species, as has been

documented in the lower basin. The Colorado squawfish and

humpback sucker have become rare during the first half of the

~Oth Century. During this same period the channel catfish

became well established. The addition of an abundant camivore

to the fish fauna has created additional competition for space

and food. More recent introductions of now abundant small

,
cypr1n1ds (specifically the red shiner) have created more

competition for space and food with juvenile fish. This

hypothesis may partly account for the lower abundance of

endemic fishes in the Colorado River as compared with similar

areas in the Green River. II

SUIIIIIlary
1. Thirty-four stations on the San Juan River and ~ts major tributaries

were lInmpled during May and August of 1976, with a variety of collecting gear.

2. Twenty-one species and one inter-subgeneric hybrid were taken. Of

these only five native species were represented, one in greatly reduced numbers.

3. The Colorado squawfish, humpback sucker, bony tall. and humpback chub

were not taken during the survey.

4. Sll~ distributional maps were generated for each species.

5. Additional intensive surveys are needed of the mainstream from

'arming ton to Lake Powell. particularly the deep Canyon areas below Bluff, Utah.

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