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Last modified
7/14/2009 5:02:36 PM
Creation date
5/20/2009 10:07:40 AM
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UCREFRP
UCREFRP Catalog Number
9499
Author
Osmundson, D. B.
Title
Removal of Non-native Centrarchids from Upper Colorado River Backwaters, 1999-2001
USFW Year
2003.
USFW - Doc Type
Summary of Results.
Copyright Material
NO
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monitored (Chart and Lentsch 1999). <br />Colorado pikeminnow YOY did not increase in abundance in the reach from <br />which non-native centrarchid and other non-minnow species were removed, based on <br />ISMP fall seine surveys of backwaters. No YOY Colorado pikeminnow have been <br />captured during ISMP monitoring between Palisade and Westwater since 1992 (McAda <br />and others 1994 to 1999, C. McAda, personal communication), including the years of <br />centrarchid removal (1999-2001). One yearling-size Colorado pikeminnow (122 mm <br />TO was electrofished during centrarchid removal efforts at rm 157.1 during fall 1999. It <br />was captured from a very small, completely isolated backwater that contained no <br />centrarchids and was found in association with red shiners, sand shiners and fathead <br />minnows. This was the only juvenile-size Colorado pikeminnow discovered in <br />backwaters during the three-year effort. <br />DISCUSSION <br />This project was not a research effort designed to answer specific questions <br />regarding the ecology of centrarchids (habitat preferences, suitability or availability of <br />environmental conditions for reproduction, etc.), the estimation of centrarchid absolute <br />abundance in backwaters (mark-recapture or depletion population estimation), or the <br />effects of centrarchids on native fishes (diet analysis, etc.). Instead, it was designed as a <br />centrarchid removal effort with the goal of increasing endangered fish survival in upper <br />Colorado River backwaters. Nonetheless, some observations and conclusions can be <br />drawn from the data collected. <br />Results presented here indicate that green sunfish and largemouth bass were more <br />ubiquitous and abundant in upper Colorado River backwaters than previously reported. <br />Nesler (2002) reported few centrarchids in seine surveys of upper Colorado River <br />backwaters during 1986-1991 (total of 458 -- all species combined). This was during a <br />time when relative abundance of centrarchids was lower than it has been in recent years, <br />at least according to annual ISMP seining results (Fig. 8). Hence, the disparity in results <br />19
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