7336

• UCREFRP Catalog Number: 7336
• Author: Valdez, R. A. and B. C. Nilson.
• Title: Radiotelemetry as a Means of Assessing Movement and Habitat Selection of Humpback Chub.
• USFW Year: 1982.
• USFW - Doc Type: Grand Junction, Colorado.
• Copyright Material: YES

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Fish with transmitters were found in water as deep as 15 m while
those without transmitters were found in a maximum depth of 12.5 m
(Figure 3). Data from fish without transmitters indicates a selection
for water less than 5 m deep. Data from the radio-tagged fish shows the
same general pattern, but indicates a greater use of water deeper than
about 7 m. This phenomenon is probably an artifact of sampling; electro-
fishing is most effective in shallow water or with fish close to the
surface in deep water. Radiotelemetry was most effective in water less
than 6 m, but enabled monitoring of those fish that positioned themselves
in midwater of a deep area. At no time in this investigation, except
with fish caught in entanglement nets, could the position of a fish in
the water column be determined. Thus, all measurements were taken of
total water depth at the capture or monitor site.

The velocity occupied by fish without modules was 0-3.8 fps and that
by radio-tagged fish was 0.2-1. 3 fps. The distribution of these two data
sets is similar with apparent selection by the species for less than 1
fps velocity (Figure 3). Water velocity measured in a deep area like
Black Rocks can be tenuous. There appears to be much tl sheet ing" and
"1ayering"of velocities when measured in vertical profile, especially
during runoff. A fish may thus be situated in a layered region of quiet
. .water but velocity recorded at six-tenths of the water depth may indicatj!
a moderate to strong velocity. High turbidity precludes accurate
measurement of these microhabitats.

Swimming performance tests in the laboratory (Bulkley et ale 1981)
showed that humpback chub were capable of sustained swimming speeds of
2.2 ft/sec for a matter of minutes at 20oC, compared to speeds of 1.6
ft/sec for Colorado squawfish, 1.47 ft/sec for razorback sucker, and 1.9
ft/sec for bony tail chub.. These results and the field observation of
this study indicate that humpback chub are capable swimmers in swift
water but prefer to spend most of their time in the. quiet areas.

The same four substrates were used by radio-tagged fish as by non-
tagged fish (Figure 3). Sand and bedrock were most often used by the
former and sand and boulder were most often associated with the latter.
These substrates appear to reflect those available in the study area,
Black Rocks.

Spawning

Radiotelemetry with humpback chub was initiated primarily to aid in
locating spawning sites and assessing spawning conditions for the
species. Water temperatures and flows in 1981 were affected by below-
normal snow fall, and the chubs spawned earlier than expected.

The spawning period in 1981 was 15-27 May at water temperatures of
l6.0-16.50C and flow of 3000-5000 cfs. Spawning in 1980 occurred 2 weeks
later, about 2-15 June, at water temperatures of 11.5-16.0.C and flows of
21,500-26,000 cfs.

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