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EXECUTIVE SUMMARY An important recent initiative of the Recovery Program for the endangered Colorado River fishes has been control of introduced fishes. Introduced species have been implicated in the decline of endangered fishes nation wide because of predation or competition for food or space. A survey of knowledgeable upper-basin biologists identified several species that are believed to have negative effects on the endangered fishes of the upper Colorado River basin; 46% of respondents believed northern pike Esox lucius to be an important problem for the native fish community. Northern pike were stocked into Paonia Reservoir on the North Fork of the Gunnison River in 1969 and 1971. Some fish escaped and established a small population within critical habitat on the Gunnison River near Delta, Colorado. No reproduction has been documented in the Gunnison River and the population apparently relies on continued escapement from Paonia Reservoir to maintain itself. This study was conducted to determine if the population could be substantially reduced through mechanical removal. Previous work identified a 16-km-long river reach downstream from Hartland Diversion where most northern pike were collected. Sampling efforts targeted that reach. Sampling was concentrated in spring when high water provided quiet, off-channel habitats that were believed to attract northern pike. Workers used electrofishing, fyke nets and trammel nets to intensively sample areas where northern pike had been collected in the past. In contrast with other studies, shoreline electrofishing was the most effective sampling technique for collecting northern pike in the Gunnison River. A total of ten northern pike were collected and removed from the study area in 1995 and 1996. Six of those pike were captured on the first day of sampling in 1995. Intensive sampling by two-person crews for 27 more days captured three more northern pike. Thirteen days of sampling in 1996 captured one additional northern pike. One pike was observed that could not be captured. The abrupt decline in catch per effort and the sustained low catch rate thereafter indicate that a small population with limited recruitment can be substantially reduced with mechanical means. It is unlikely that all northern pike occupying iv