7153

• UCREFRP Catalog Number: 7153
• Author: Holden, P. B.
• Title: Study of the Habitat Use and Movement of the Rare Fishes in the Green River, Utah.
• USFW Year: 1978.
• USFW - Doc Type: Logan, Utah.
• Copyright Material: NO

adults, a rather flat head, and a tendency for a subterminal mouth
suggest the humpback chub, although the robustness of the fishes
and the slightness of the nuchal humping suggest the roundtail
chub (Gila robusta). Until a more thorough analysis of these
fishes is finished9 the Desolation-Gray canyons' specimens will be
referred to as humpback chubs, except for one instance where the
specimen appeared to be a bony tail chub, as mentioned below.
One adult bony tail chub was collected in the upper portion of
the study area.~__juvenile chub was caught in Desolation Canyon
that had dorsal and anal fin ray counts of 10-10, and a less ob-
vious nuchal hump and flattened head than other chub specimens
from that area. These characteristics suggest the fish was a
juvenile bony tail chub.
Preferred Habitat of Rare Fishes
The preferred depth, velocity, substrate, habitat type, and
temperature of the rare fishes are summarized as e1ectivity curves
(Figures 2-9). Colorado squawfish young-of-the-year were found
only in backwaters where there was no current, a firm silt bottom,
and a depth of one to two feet (Figure 2). Juvenile squawfish al-
so preferred backwaters, no current and a silt bottom, but were
less selective with depth (Figure 3). Subadu1t and adult squaw-
fish (200+ mm) were found in a variety of velocities and depths,
but preferred sandy bottomed eddies and runs to backwaters (Fig-
ure 4). Squawfish of all sizes showed little preference for

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