Northern Pike Removal Smallmouth Bass Monitoring and Native Fish Monitoring in the Yampa River, Hayden to Craig Reach, 2004-2006

摘要

Northern pike (Esox lucius) is a large aggressive, esocid native to many North American drainages that has been widely stocked outside of its natural range. Smallmouth bass (Micropterus dolomieu) is an exotic predatory fish present in the Yampa River. The Upper Colorado River Endangered Fish Recovery Program has established an active program to control nonnative fishes in the main rivers of the upper basin to assist in recovery of the endangered fishes. Objectives of this study are 1) to reduce numbers of the adult northern pike population in the study reach, 2) determine northern pike abundance and size structure in the study reach and the subsequent changes in the abundance and structure after removal, 3) determine if sampling (removal) concentration areas is effective, 4) maintain public support for the Recovery Program by providing off-channel angling opportunities, and 5) to monitor the native fish community and smallmouth bass population in the study area and 6) monitor movement of smallmouth bass and northern pike. Adult northern pike abundance estimates declined after a total of 2267 northern pike were removed from the river. Catch rates also declined within all years although no significant trends were detected. Mean length of northern pike captured varied by year and pass. Northern pike moved upstream and more often downstream between and within years. Northern pike angling tag returns from water where they had been relocated were 25% in 2004, 5% in 2005 and were not estimable in 2006. Recapture rates of smallmouth bass tagged within the study area were very low making movement and abundance estimates difficult. The native fish community in the study area is poorly represented.