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. DISCUSSION . Catch Per Unit Effort During the six years of the removal effort for northern pike, electro fishing and trammel netting catch rates decreased; fyke netting catch rates have varied, but essentially decreased over the years (Table 1). This is true also for northern pike catch rates during other projects in the middle Green River, such as the Colorado pikeminnow abundance estimates and smallmouth bass removal (Table 3). Among all gear types, electrofishing was the most efficient gear type throughout the entire study, although trammel netting was efficient at capturing northern pike in most years when used in conjunction with electro fishing (Table 1). In comparison with catch rates in parts of the basin with established pike populations (i.e., the Yampa River), catch rates in the middle Green River are low and effort is considered to be at a preventative level (i.e., with minimal effort we are removing a similar number of northern pike each year and preventing the establishment of a reproducing northern pike population). Specific efforts to control northern pike in the middle Green River have decreased from 2001 (19.1 electrofishing hours; 421 fyke net nights; and 37.7 trammel netting hours) to 2006 (3.3 electrofishing hours; 52 fyke net nights; and 2 trammel netting hours). . . . . . . Factors Affecting Catch Rates Because this was a six -year study period, many things changed over the years that may have influenced these catch rates (besides a decrease in the number of northern pike in this reach): flows, net placement, equipment issues, and crew turnover. . . 22 .