7402

• UCREFRP Catalog Number: 7402
• Author: Nesler, T. P.
• Title: Aquatic Nongame Research, Endangered Fishes Investigations.
• USFW Year: 1989.
• USFW - Doc Type: Fort Collins, Colorado.
• Copyright Material: NO

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Floy tag near the base of the dorsal fin. Scale samples were also collected
from all northern pike. Colorado squawfish captured were also measured for
length and weight, existing Carlin tag numbers noted, and scale samples
collected for age-growth analyses under a separate study. All of these fish
were then released. Other fish species collected were enumerated by species
and also released. Other data collected at sampling sites included date,
time, river mile location, habitat type sampled, presence and location of
adjoining habitat types, water temperatures in habitat sampled and main
channel, and presence of submerged cover or aquatic vegetation.
When northern pike of a suitable size were collected during sampling of a
given reach in the fall, these fish would be used for surgically-implanted
radio transmitters and radio tracking observations. This phase of
investigation was initiated in October 1986 by CSU Larval Fish Lab (LFL)
personnel using surplus radio transmitters made available by cnow Northwest
Region fish biologists. Seven northern pike were implanted with transmitters
at that time, and tracking observations were made on these fish through the
1986-87 winter season by the LFL crew. Seven transmitters remained from this
surplus, and were used in this study during the 1987 fall season to implant an
additional seven northern pike. Techniques for implantation and observation
were similar for LFL and cnow radio-tracking efforts and are described below.
Candidate northern pike for implantation were determined by a minimum size
of 600 rom total length. These fish were placed in a large, oval tub and
examined for injury or abnormal behavior following electrofishing or removal
from the nets. The select fish would then be anesthetized with MS-222, and
processed through length-weight-Floy tagging-scale sample procedures prior to
implantation surgery. The anesthetized fish would then be placed belly-up in
a V-shaped wooden trough. Surgical procedure consisted of removing scales
from an area just posterior to the pelvic fin girdle using forceps to permit a
30-35 rom length incision through the body wall using a curved-blade scalpel.
This allowed the incision to be made while using the blade to lift the body
wall away from the internal organs and minimize risk of internal injury. A
capsule-shaped, 30 MHz radio transmitter, approximately 5 em long by 2 em
diameter and coated in beeswax, would then be placed through the incision and
pushed forward over the pelvic girdle with one finger. The incision was then

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