7908

• UCREFRP Catalog Number: 7908
• Author: Valdez, R. A. and R. J. Ryel.
• Title: Life History and Ecology of the Humpback Chub ‎(
• USFW Year: 1995.
• Copyright Material: NO

Final Report

SCOPE OF WORK

The scope of work for this investigation was based
on a sampling program that provided an
understanding of the life history and ecology of the
humpback chub and simultaneously addressed
hypotheses on effects of Glen Canyon Dam
operations. The nature of the study objectives
required an integrated approach to link humpback
chub life history requirements with physical,
chemical, and biological components of the
environment that are potentially affected by dam
operations. A compr~hensive understanding of life
history requirements was required to evaluate.
limiting factors.

Although the humpback chub was described in 1945
(Miller 1946) and periodically studied since the late
1960s, only general life history information and
schedules are known. While the population in
Grand Canyon is the most intensively studied, the
focus of investigations has been on the LCR rather
than on the mainstem Colorado River. The lack of
information on the humpback chub required parallel
and sometimes simultaneous assimilation of life
history information and hypothesis development and

Existing Life
History
Information
of Humpback
Chub

Ongoing
Study

Accumulated
Information
and
Data

Evaluate Effects
of Dam Operation

<H:
H2
o

Introduction . 1-5

testing (Fig. 1-3). Limiting factors were identified
and explained through a process of life history
descriptions leading to multiple sequential
hypotheses and multiple parallel hypotheses
(Schumm 1991). Hypotheses were developed as
ideas or propositions to provide ~ foundation for
explaining certain phenomena. This approach was
used to focus the study design on an evaluation of
effects with a dedicated data collection protocol.

Flow characteristics of the Colorado River in Grand
Canyon varied during this investigation and have
varied dramatically since Glen Canyon Dam began
impounding water on March 13, 1963 (See Chapter
3 - HYDROLOGY). Hence, the scope of work for
this investigation focused on operational
components (i.e., magnitude of fluctuations,
minimum and maximum discharges, and rates of
change in fluctuating discharges) rather than
operational regimes because of the varied flow
characteristics. Operational regimes during this
investigation included "research flows" (June 1,
1990 through July 29, 1991) and "interim flows"
(August 1, 1991 through completion of this field
investigation). The short duration of each of these
flow scenarios precluded identifying, isolating, and

Data
Integration

Present
Understanding
of Life
History of
Humpback
Chub

Sequential
and Parallel
Hypotheses
Development
H3
o
H4
HOs
o
H6
o
H'
o

Final
Hypotheses
Testing

Reject
Accept
Reject
Accept
Reject

Fig. 1-3. Relationship of assimilation of life history information and hypothesis development and testing.