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

deadline occurs June 30, 1988, but this occurs in the middle of the 1988 field
season. For the sake of completeness, this report will include data collected
through October 1988.

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METHODS

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Yampa River
Intensive sampling using electrofishing, netting, seining and angling were
conducted in four distinct reaches of the river during July through November
1987, and from April through October 1988. Study area reaches (Figure 1)
included Lilly Park-Deerlodge Park (river miles=RM 45-56), Maybell-Sunbeam (RM
58-90), Juniper Springs (RM 90-114), and Hayden-Craig (RM 115-170).
Preliminary field work served a two-fold purpose. One was to collect data on
abundance, distribution, reproductive success, and age/size structure of
riverine populations of non-native, non-salmonid gamefish species present.
The second was to obtain northern pike adults suitable for radio-transmitter
implantation. These fish were radio tracked to determine seasonal habitat use
and suggest movement and .habitat needs related to spawning.
Due to varying flow level throughout the year, sampling techniques had to
be varied as well. During pre-runoff and runoff river flows from April to
June, radio tracking and sampling gear transport was conducted prim~rily using
a flat-bottomed john boat powered by an outboard jet unit. Another similar
john boat with electrofishing capability was also used when flow conditions
warranted. Field experience gained from continuous shoreline shocking in
these same river reaches during standardized spring monitoring indicated a
sporadic abundance of northern pike, and those affected by the electric field
could be observed but not easily captured. As might be expected, channel
catfish were also not particularly vulnerable to this sampling technique and
few were encountered during standardized monitoring surveys. A "block and
shock" technique was developed in conjunction with CSU Larval Fish Lab
personnel familiar with radio tracking work on the Yampa River. The essence
of the technique was to place either trammel or gill nets in river habitats
that appeared suitable for the target fish species and subsequently create
some disturbance in these habitats to initiate fish movement, thereby
increasing the capture potential of the passive net. In practice, this meant

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