7321

• UCREFRP Catalog Number: 7321
• Author: U.S. Fish and Wildlife Service.
• Title: Fish and Wildlife Service Upper Colorado River Basin Technical Advisory Study Important Reach Analysis - CRFP.
• USFW Year: 1984.
• USFW - Doc Type: \
• Copyright Material: NO

, In: distribu!ion of Colorado squawfish larvae collected in 1981, 82
and 83 were plotted by size class and are presented in Table 1. The distribution
of larvae smaller than 15 mm is as follows, presented by river mile iocatior.:
Green = 66.4,116-130,176, 224-251,290-315; Yampa = 0.1-18. The distribution
of 'larvae under 25 mm in size is continuous from river mile 0 to 315 in the
Green and from 0 to 18 in the Yampa (Table 2). ihe larval distribution
were compared with the location of radiotagged Colorado squawfish (Figure 1),
the collections of ripe fish, and substrate to arrive at a matrix (Table 3)
that delineates river miles for the two criteria. Four areas were classified
as spawning locations and three areas as suspected areas. One area met
every criteria but substrate and should be further evaluated in the future,
since some does occur in the horseshoe bend area "immediately upstream.

La rvae (< 251T1Tl)

Larval drift areas have been identified in Tables 1 and 2. The
distribution of <:25mm larval Colorado squawfish is continuous in the
mainstem Green from RM 0 to 315 and from RM 0 to 18.2 in the Yampa.
Areas of high concern for temperature in the mainstem rivers should at
least i~clude the areas in Table 1 where <:15mm larvae occur: Green RM 66;
116-130; 176; 224-251; 290-315; Yampa RM 0.1 to 12.2.

Youna-cf-the-year (25-60 rom)

Loca ti on:

Criteria were developed for designation of young-of-the-year nursery
reaches. These were:

Concentration areas:

1. Average catch per eff02t for years of record of YOY with
seines exceeds 0.9/10m .

2. Presence of significant backwaters.
3. Presence of silt/sand substrate.

4. Low gradient

Major nursery area:

~
I.

,.,
Catch per effort of young-of-the-year greater than O.Og/lOm~.

2.

Presence of significant backwater areas.

"
....

Presence of silt/sand substrates~

4.

Low gradient