8005

• UCREFRP Catalog Number: 8005
• Author: McAda, C. W.
• Title: Mechanical Removal Of Northern Pike From The Gunnison River, 1995-1996.
• USFW Year: 1997.
• USFW - Doc Type: 58,
• Copyright Material: NO

STUDY GOAL AND OBJECTIVES
Goal: Prevent colonization of restored flooded-bottomland habitats by introduced predators,
especially northern pike.
Objectives: 1. Evaluate standard techniques for efficient removal of nonnative predators.
2. Estimate relative decline in nonnative predators as a result of fish removal.
3. Determine short-term reinfiltration rates of nonnative predators back into
important habitats.
METHODS
Burdick (1995) identified locations and time periods when nonnative predators were
concentrated. As noted above, all but two of the northern pike collected by Burdick were
between river kilometer (RK; distance upstream from confluence with Colorado River) 86.7
and 117.8. Further, 13 of those 18 fish were collected in a 2.9-km-long reach immediately
below Hartland Diversion (RK 96.4). Two of the remaining pike were captured in a flooded
area at RK 86.7 and three were captured upstream from Hartland Diversion. For this study,
sampling efforts were concentrated in a 16-km-long reach downstream from Hartland
Diversion (Figure 1) where Burdick (1995) captured 15 northern pike. Three different
sampling gears (electrofishing, trammel nets, and fyke nets) were used to collect fish during
the 2-year study. Electrofishing was used in shoreline habitats when water conditions were
suitable. Water level was generally too low to shock effectively during summer and too high
for safe sampling during peak runoff. Quiet-water habitats were sampled with- trammel nets
and fyke nets. Trammel nets were usually used as part of the 'scare and snare' technique
(blocking the mouth of a backwater and driving fish into the net by creating a disturbance in
the backwater; sensu Osmundson and Burnham 1996), but were also used in stationary sets
for one or two hours at a time. Fyke nets were used in overnight sets in flooded areas out of
the main current where northern pike might be expected to congregate. They were set in a
variety of quiet, flooded-vegetation habitats including an old oxbow where Burdick (1995)
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