First Reproduction by Stocked Bonytail in the Upper Colorado River Basin

Abstract

Bonytail Gila elegans, a large‐bodied cyprinid that is endemic to the Colorado River basin of the American Southwest, was historically widespread and abundant in large warmwater streams but is now critically endangered. To increase recovery prospects, over 500,000 Bonytails have been stocked in the upper Colorado River basin since 2000, but adult survival has been low and reproduction has not been detected. We provide the first documented evidence of successful reproduction by stocked Bonytails in the upper Colorado River basin. Adult Bonytails were stocked in the Green River and accessed Stewart Lake and Johnson Bottom (managed floodplain wetlands in the middle Green River, Utah) during high flows in May 2015 (Stewart Lake only) and 2016. Draining of Stewart Lake in September 2015 revealed 19 age‐0 individuals of Gila sp. (37–64 mm TL) among over 405,000 fish. Four preserved specimens (41–48 mm TL) were verified as Bonytails by using morphological and molecular techniques. Otolith daily increment analysis confirmed reproduction by Bonytails in Stewart Lake. Bonytail reproduction was also noted during 2016 in Stewart Lake (probable) and Johnson Bottom. Young Bonytails survived despite the presence of abundant nonnative fish predators. Use of floodplain wetlands for reproduction may enhance the recovery of critically endangered Bonytail in the upper Colorado River basin. Received September 1, 2016; accepted January 2, 2017 Published online March 15, 2017

Hatchery‐reared endangered Colorado pikeminnow (Ptychocheilus lucius) undergo a gradual transition to piscivory after introduction to the wild

“…Similar to other endangered fishes in the Colorado River Basin in south‐western USA (Bestgen et al, ; Schooley & Marsh, ; Zelasko, Bestgen, & White, ), a captive breeding programme has been established to aid the recovery of federally protected Colorado pikeminnow Ptychocheilus lucius Girard, 1856 (Figure ). The endemic Colorado pikeminnow was once widespread throughout the Colorado River Basin (Holden & Wick, ; Miller, ), but during the last century suffered dramatic declines because of habitat fragmentation and environmental alteration (US Fish and Wildlife Service, USFWS, ).…”

Factors Influencing Capture and Retention of Razorback Sucker in Light Traps

“…The Green River basin supports some of the largest populations of endangered and nonlisted native fishes in the basin (Bestgen 2015), and two middle Green River spawning locations for Razorback Sucker are known (Muth et al 2000; Bestgen et al 2011; Zelasko et al 2018). Spawning occurs in spring on the ascending limb or peak of the hydrograph, and correctly timed flows of sufficient magnitude transport larvae downstream into warm, food‐rich floodplain wetlands (Tyus and Karp 1990; Wydoski and Wick 1998) that promote rapid growth and increase their survival (Modde 1996; Modde et al 2001; Bestgen 2008; Bestgen et al 2017).…”

Light Trap Effectiveness to Capture Razorback Sucker Larvae in a Large Floodplain Wetland

“…In the upper Colorado River basin, Razorback Sucker typically spawn in streams on the ascending limb or peak of the spring hydrograph, with subsequent downstream dispersal of drifting larvae (Tyus and Karp 1990; Wydoski and Wick 1998). Reproduction timing coincident with flood flows increases larvae access to wetland habitats, which provide plentiful food and warm water temperatures crucial for increased growth and survival (Modde 1996; Modde et al 2001; Bestgen 2008; Schelly et al 2016; Bestgen et al 2017). Currently, flows from upstream Flaming Gorge Reservoir are released after Razorback Sucker larvae are first detected to maximize their entrainment into floodplain wetlands per the Larval Trigger Study Plan, Upper Colorado River Endangered Fish Recovery Program (Brower et al 2001; Hedrick et al 2009; Bestgen et al 2011; LaGory et al 2012).…”