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We evaluated patterns of space use, activity, and agonistic interactions between young Ptychocheilus lucius, an endangered cyprinid, and similar-size individuals of native and non-native fishes (i.e., Catostomus latipinnis, Notropis lutrensis, Richardsonius balteatus, Pimephales promelas, Lepomis cyanellus, and Ameiurus melas), which co-occur in shoreline riverine habitats. Vertical distribution of P. lucius was most similar to that of L. cyanellus and R. balteatus. We detected no overt shifts in vertical space use by P. lucius due to the presence of non-native fishes. Lepomis cyanellus, N. lutrensis, and Pimephales promelas initiated more interspecific aggression than Ptychocheilus lucius. Agonistic behavior in...
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Qualitative scoring is frequently overlooked in preference to counts or measurements of individual characters, particularly for species whose overlap in morphology makes clear separation difficult. Quantitative measurements and counts of single characters were compared to qualitative rankings of selected morphological features of chubs (genus Gila) from the Yampa River, Colorado. Data were collected by technicians with no specialized training in systematics. A high degree of morphological variability confounded identification using the quantitative data set, while principal components analysis of qualitative data clearly separated Gila cypha (humpback chub) and G. robusta (roundtail chub). Totals of 32 G. cypha...
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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 nonfish items (2.4%). Red shiner, Notropis 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%) ; of 6...
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Habitat use and movements of young Colorado squawfish Ptychocheilus lucius were determined by seining 1,194 of the fish in shoreline areas. A total of 922 of these was fin-clipped in selected habitats and 230 (25%) were subsequently recaptured. Most young Colorado squawfish were captured in shallow shoreline embayments (backwaters; 85% of captures), where they were most abundant in spring (April; 68%). Some individuals used more than one habitat and moved between backwaters, shoreline eddies, and main-channel runs. A diel pattern of backwater use was associated with warmer water temperatures, especially in spring (April) when backwater temperatures exceeded river temperatures. Published in Journal of Freshwater...
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In the Yampa River, stream habitat needs and life history requirements of Colorado squawfish (Ptychocheilus lucius), humpback chub (Gila cypha), razorback sucker (Xyrauchen texanus), and other native Colorado River fishes are presently maintained by flow regimens approximating natural conditions. Yampa River flows are also important in reducing adverse water management practices in the downstream Green River. Management for recovery of endangered fishes in the Yampa River will require specific flows to provide seasonal requirements at different locations: high spring flows associated with the initiation of Colorado squawfish spawning migrations, humpback chub and razorback sucker spawning, and maintenance of spawning...
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