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the floodplain should be investigated. In addition, rock or concrete rip-rap should be <br />removed from shorelines where it currently provides beneficial cover to centrarchids. <br />These and other techniques should be considered in the development of future control <br />strategies <br />CONCLUSIONS <br />Relative abundance of centrarchids, especially largemouth bass and green sunfish, <br />in backwaters and seasonally isolated side channels was much higher than <br />previously reported. <br />2. Barge-electrofishing was much more effective in capturing centrarchids than was <br />boat-electrofishing. Boat electrofishing was most effective at capturing adult <br />carp. <br />3. A one-pass electrofishing approach repeated twice annually for three years <br />evidently failed to reduce centrarchid populations, based on electrofishing catch <br />rate results. <br />4. There was no increase in YOY Colorado pikeminnow during the centrarchid <br />removal period, indicating that if numbers of young are affected by centrarchid <br />predation, effective `control' of centrarchids was not realized. <br />RECOMMENDATIONS <br />1. Conduct studies to determine whether backwater-dwelling centrarchids are <br />primarily originating from existing populations within floodplain channels and <br />backwaters (self-sustaining) or from off-channel sources via irrigation returns <br />(obligatory chronic immigration). <br />2. Determine distribution of centrarchids in backwaters upstream of the Grand <br />Valley. <br />24