7193

• UCREFRP Catalog Number: 7193
• Author: Nesler, T. P.
• Title: Aquatic Nongame Research, Squawfish-Humpback Studies.
• USFW Year: 1987.
• USFW - Doc Type: Fort Collins, Colorado.
• Copyright Material: NO

2

Job 1. Standardized monitoring surveys

Objective:

To determine the status and trends in the populations of the
endangered Colorado River fishes in relation to physical or
biological changes in the river environment, or to different
management or recovery measures.

Methods

This program is described fully in a field procedures and data analysis
handbook (U.S. Fish and Wildlife Service 1986). The Colorado Division of
Wildlife has responsibility for the following tasks outlined in the monitor-
ing schedule:

A. Spring - Late juvenile/adult Colorado squawfish

1. Yampa River
a. Above Juniper Springs (RM 105-95, Reach Code 9).
b. Maybell to Sunbeam (RM 80-70, Reach Code 10).
c. Cross Mtn. to Lily Park (RM 54-49, Reach Code 11).

2. Colorado River
a. Loma to Stateline (RM 152-132, Reach Code 6).

3. White River
a. Below Kenney Reservoir (RM 105-95, Reach Code 12).

B. Fall - Post-larval, Age-O Colorado squawfish

1. Colorado River
a. Grand Junction to Ruby Canyon (RM 170-140).

For the spring monitoring schedule, each river reach was divided into at
least two subreaches to provide replicate samples. One shoreline of each
subreach (5-mi. long) constituted one sample. Sampling was done by electro-
fishing along both shorelines of all reaches by boat. Sampling was done
downstream at a steady pace with all habitat features being sampled once as
they were encountered. Sampling time was measured to the nearest second
with an elapsed time clock located on the variable voltage pulsator. All
captured Colorado squawfish were measured for total length, weighed and
tagged with a color-coded and numbered Carlin tag. The fish were then re-
leased at the original capture site. Numbers of Colorado squawfish observed
but not captured were also recorded at the end of each sample. Total number
of warmwater gamefish species observed during sampling was also noted at the
end of each sample.

For the fall monitoring schedule, sampling was conducted with a 3.2 mm
ace mesh beach seine, 4.6 m long by 1.2 m deep. The river reach was divided
into 5-mile long sections. As the sampling crew progressed downstream in
each section, the first suitable backwater encountered would be sampled.
This backwater was defined as a primary backwater, and should be at least
30m2 in surface area and at least 0.3 m deep at its deepest point. The
primary backwater was sampled with two, non-overlapping seine hauls which