9314 ‎(2)‎

• UCREFRP Catalog Number: 9314
• Author: Wick, E. J. and J. A. Hawkins.
• Title: Colorado Squawfish Winter Habitat Study.
• USFW Year: 1989.
• USFW - Doc Type: Fort Collins.
• Copyright Material: NO

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Northern pike (Esox lucius) were radiotagged in all study areas in
cooperation with CDOW to determine habitat use and movement during winter and
spring and to gather spawning data. During Winter 1, northern pike were
radiotracked only at locations where Colorado squawfish were present. All
northern pike radictags were on the 30 MHz frequency band as opposed to the 40
MHz Colorado squawfish band. Consequently, tracking the two species required
different radio receivers and loop antennae. If northern pike were detected,
habitat use, depth, velocity, and distance from squawfish were recorded.
During Winter 2, CDOW research personnel tracked northern pike throughout the
winter; therefore, our efforts were less intensive during winter but were
intensified during spring when we tracked both squawfish and northern pike.
Fish were tracked on a biweekly schedule during fall 1987 (Table 1). On
each trip, an attempt was made to contact all fish by floating in a canoe
through each study area. When fish were located, they were monitored to
obtain two 15-minute observations at a stationary location. In addition, two
fish were monitored each week for an additional 4-hr period. 'These long-term
observations were systematically alternated between the three study groups and
three 8-hr daily time periods. This study design provided an observation in
each of the 8-hr time periods in all three study groups while ensuring that
different groups and time periods were monitored each week. The 8-hr time
periods were: 0401-1200, 1201-2000, and 2001-0400. The starting time of each
4-hr observation period was randomly selected from the first 5 hr in each 8-hr
daily time period. One fish from each group was selected without replacement
from those found on each biweekly trip. The fall long-term sampling design
included observations on a total of nine fish (three fish from each of three
groups covering each of the three daily time periods in each group). Physical
habitat measurements were recorded at each location at which a fish spent 15
minutes.
During Winter 2, fish were tracked in all three study areas on each
biweekly trip. Fish were monitored as they were located in each study area.
Two 15-minute observations were obtained on each fish located. Study areas
were sampled according to a systematic schedule. Long-term observations were
shortened from 24 to 2.5 hr and were made during twilight periods to ensure
that times early and late in the day would be adequately represented in the
data base. on each biweekly trip a fish was monitored during the morning and
evening twilight periods according to a systematic sampling design.
t Habitat measurements Winter 1
At the conclusion of a monitoring period, habitat measurements were taken
' at all sites at which fish spent 30 or more minutes. Sites were determined by
triangulation from 2 to 5 transects which were previously marked by survey
flags placed along the bank during monitoring. Measurements taken were water
depth, velocity, substrate, cover, and water temperature. When fish habitat
was free of ice, measurements were taken from a boat or by wading. When ice
formed over the site and was considered unsafe to walk upon, access to the
fish location was achieved by sitting in a small inflatable raft at waters
edge and pushing it over the surface of the ice using a wading rod. Throughout
most of the winter the ice was thick enough to walk upon safely. However, a
small inflatable raft was often taken out on the ice as a safety precaution
and to carry measurement equipment. Depth was measured using a 10-foot depth
rod (1\2 inch electrical conduit marked in 0.1 foot increments). Velocity was

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