7364 - Laserfiche WebLink

Home Browse Search

~~~ I ~~ ~ ~~~~ f ~ Esox lucius (Esocidae), and Stizostedion vitreum (Percidae) in the Green River Basin, Colorado and Utah Harold M. Tyusl and James M. Beard2 Abstract.-Northern pike, Esox lucius, stocked in the Yampa River in 1977, invaded the mainstream Green River by 1981, and subsequently increased in ~ ~~~ range and abundance. The speed of this invasion is indicated by two recaptured pike that moved 78 and 110 km, respectively, downstream in about one year. Pike stomachs (n = 123) were usually empty (54.5%), but some contained fish (43%) and non-fish items (2.4%). Red shiner, Notro is lutrensis, and fathead minnow, Pimephales promelas, predominated among the 12 fish species eaten. Walleye, Stizostedion vitreum, presumably introduced to the Green River drainage in the 1960s, was widely distributed but low in abundance. Most of 61 adult walleye stomachs contained food (60.7%) and of 6 fish species eaten, channel catfish, Ictalurus punctatus, and fathead minnow were most frequently consumed. Northern pike and walleye were captured in habitats occupied by endangered Colorado River fishes, particularly Colorado squawfish, Ptychocheilus lucius. Predation on endangered fishes was not detected, but northern pike and walleye consumed at least three other native fishes. The northern pike may pose a threat to endangered fishes due to its population expansion, piscivory, and resource sharing. Diets of both species should be further evaluated if their abundance increases. lU.S Fish and Wildlife Service, 1680 W. Highway 40, Vernal, Utah 84078 2Present address:1361 Vernon St., Eureka, CA 95501 1