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Last modified
7/14/2009 5:02:30 PM
Creation date
5/22/2009 4:52:49 PM
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UCREFRP
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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<br />setting nets in low flow habitats and using electrofishing to either capture <br />target fish species outright or drive fish into the nets. <br />This technique appeared particularly effective in the spring when rising <br />river flows created side channel and tributary backwaters that could be <br />completely blocked from the main channel with nets. Using the jet boat, a net <br />was extended across the mouth of the backwater. Prior to complete blocking of <br />the backwater, the electrofishing boat would be passed into the backwater <br />channel with the backwater mouth blocked immediately afterwards with the net. <br />This was all performed manually if possible to eliminate engine noise from <br />disturbing fish prematurely. Northern pike, channel catfish, and Colorado <br />squawfish appeared quite susceptible to this "block and shock" approach <br />judging from sample sizes compared to continuous shoreline shocking. Nets <br />used in this process included 30.5 m trammel nets, 1.8 or 2.4 m deep, with 150 <br />rom mesh outside walls and 25 rom inner wall; or a 38 m monofilament gill net, <br />1.8 m deep with five experimental mesh panels ranging from 12.7-44 mm mesh <br />sizes. The electrofishing boat was equipped with a Coffelt VVP-15, 5000 watt <br />generator, and single dropper cable anodes of 9.5 mID steel cable. Output <br />power was set initially at the highest level practical for stunning fish (200- <br />400 volts, 2-l0 amps) at the head end of a given backwater, usually some <br />distance from the blocked mouth. Output power was decreased near the blocking <br />net such that voltage read below 100 v and amperage was less than 0.5 amps. <br />During decreasing run-off flows and post run-off flow levels, use of the <br />electrofishing boat throughout the river reach was progressively limited due <br />to its weight. Backwater habitat was reduced and suitable habitat for net <br />sampling was restricted to select pools and large eddies. Net use was also <br />limited by drifting masses of Cladophora, which clogged the net after 30 <br />minutes or less in the river. Access to a given river reach was practical <br />during the late summer and fall seasons only by canoe. Nets would be set in <br />large pools or eddies under suitable conditions and while the nets were set, <br />crews would attempt to capture fish via angling from the shore or canoe. <br />Noise would be made using the canoe hull while floating in the pool/eddy <br />habitat in an attempt to move fish into the nets. <br />All gamefish species captured by these means were enumerated by species, <br />measured for total length, weighed, and tagged using insertion of an anchor <br /> <br />4 <br /> <br />. . <br /> <br />\( <br />
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