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Methods <br />Subadult-adult Colorado squawfish monitoring was conducted in April and May, prior to <br />peak runoff. All sampling was conducted from rigid-bottom, outboard-powered <br />electrofishing boats equipped with 4- or 5-kilowatt generators and WP-15's (or equivalent) <br />to adjust the voltage transmitted to the water. Electrofishing boats used two spherical anodes <br />suspended from booms in front and two cathodes (usually stainless steel cables) suspended <br />from each side of the boat. Investigators used direct current and tried not to exceed 300 <br />volts or 12 amps (usually held on or below 6 amps). Electrode size and shape, and voltage <br />and amperage output were adjusted regularly to minimize the possibility of injuring a rare <br />fish, while maximizing electrofishing effectiveness as much as possible. <br />Investigators began at the top of each reach and electrofished downstream at a constant <br />rate with electrical current applied constantly to the water column. Investigators did not <br />make judgements about locations that might hold Colorado squawfish and attempt to 'sneak <br />up' on fish. Right and left shorelines of all sampling reaches were each sampled once. <br />Backwaters, tributary mouths, and other habitat features along the shoreline were also <br />sampled. Because the sample reaches had different lengths (5 to 22 miles), they were <br />divided into at least two, but no more than five subreaches ranging between 2.5 and 6 miles <br />long. These subreaches remained constant after being established in the first year of ISMP. <br />Sampling began at the top of each subreach and proceeded to the bottom. If a rare fish was <br />captured within a subreach, sampling was stopped and the fish was processed and released as <br />near to the capture site as possible. Sampling began again at the location where the fish was <br />captured and continued downstream until another rare fish was captured or the end of the <br />subsection was reached. At the top of the -next subreach, data sheets were completed and the <br />elapsed-time clock was reset before sampling began again. Although different elective <br />reaches are sampled each year, fish are collected using the same sampling design as the <br />regular ISMP reaches. <br />Only rare fishes (Colorado squawfish, razorback sucker Xyrauchen texanus, humpback <br />chub, or bonytail G. elegans) or fish of special interest (e.g. northern pike Esox lucius or <br />roundtail chub G. robusta) were captured for the monitoring program. Other introduced <br />species (walleye Stizostedion vitreum, largemouth bass Micropterus salmoides, smallmouth <br />bass M. dolomieui, and green sunfish Lepomis cyanellus) that could be identified when <br />shocked were counted but not always captured. Rare fish attracted to the cathodes that were <br />14 <br />