7328

• UCREFRP Catalog Number: 7328
• Author: Suttkus, R. D. and G. H. Clemmer.
• Title: Fishes of the Colorado River in Grand Canyon National Park.
• USFW Year: 1976.
• USFW - Doc Type: R. M. Linn, ed. November 9-12, 1976.
• Copyright Material: NO

gan the habitat became unfavorable as a spawning
area for the humpback sucker. We assume that the
main Colorado immediately below the Glen CanYQn
dam is also unfavorable for the flannelmouth sucker
but because it utilizes the tributaries such as
the Paria it soon greatly outnumbered the humpback
sucker and is in the process of genetically swamp-
ing out the humpback sucker.

graph in Figure 2 is a tuberculate "male with a
stout peduncle. This specimen was collected on
May 4, 1976 from the Paria River.

The bluehead sucker, Pantosteus discobolus, is
highly variable in certain body proportions. Long
slim peduncle forms have been collected together
with short, stout peduncle forms. The upper photo-

The bluehead sucker was taken from all the
tributaries noted above for the flannelmouth suck-
er collections except for Clear Creek and Matka-
tamiba Creek. It was taken from the same main
river sites except for River Mile 65.8, 209, and
212.5. A single specimen of the bluehead sucker
was taken from Tapeats Creek on July 24, 1972.
Although two different forms of bluehead sucker
are recognized we treat them collectively herein.

FIGURE 2. (upper) Pantosteus discobolus TU 97588:200 rom SL.
77 . 1 mm SL.

(lower) Rhinichthys osculus TU 97942:

FIGURE 3. Gila cypha TL 97918:307 mm SL, 368 mm TL.
601