Survival Rates and Movement of Hatchery‐Reared Razorback Suckers in the Upper Colorado River Basin, Utah and Colorado

Abstract

We used tag–recapture data to estimate apparent survival and capture probability for 119,129 hatchery‐reared, federally endangered razorback suckers Xyrauchen texanus stocked into upper Colorado River basin streams during 1995–2005. Effects investigated included reach, year, and season of stocking; fish total length (TL) at time of stocking; survival in the first year after stocking versus in subsequent years; and sampling effort. Recapture data were also used to describe poststocking movement. First‐year survival rate for stocked razorback suckers of average TL (252.5 mm) was low: 0.05 (95% confidence interval [CI], 0.042–0.071). Total length at stocking and first‐year survival were positively correlated; survival approached zero for fish smaller than 200 mm TL but increased to 0.75 or higher for the few fish larger than 500 mm. Season of stocking had a large effect on razorback sucker first‐year survival; the predicted rate for average‐length fish stocked in summer was less than 0.02 (CI, 0.012–0.022), but it was 0.07 (0.044–0.094), 0.08 (0.057–0.100), and 0.08 (0.057–0.118) for fish stocked in spring, autumn, and winter, respectively. The overall subsequent‐year survival rate for razorback suckers was estimated to be 0.75 (CI, 0.688–0.801). Capture probabilities were relatively low, ranging from 0.002 to 0.128 for fish of average TL. The mean minimum distance traveled, elapsed time, and rate of travel by razorback suckers between recaptures were 54.7 km (range, 0–514.9 km), 254 d (0–3,164 d), and 0.87 km/d (0–55.37 km/d), respectively. Movement was more frequent out of Colorado and Gunnison River stocking reaches (36.9%; range, 30.1–100%) than Green River stocking reaches (7.7%; range, 2.9–10.3%). Our recommendations include ceasing summer stocking, performing cost ‐benefit analyses of increasing TL at stocking, employing a standardized stocking protocol, and developing a comprehensive razorback sucker monitoring program, implementation of which should enhance recovery prospects for razorback suckers in the upper Colorado River basin.

Size Sorting in Bonytail Skews the Sex Ratio of Stocked Fish

“…; Pacey and Marsh ; Bestgen et al. ; Zelasko and Bestgen ). This problem is not unique to Bonytail—many hatchery‐raised fish struggle when they are released into the wild (Brown and Day ).…”

Drought Risk and Adaptation in the Interior United States: Understanding the Importance of Local Context for Resource Management in Times of Drought*

“…The Recovery Program is intended to protect critical stretches of habitat along the mainstem of the Yampa River, from the town of Craig west 140 river miles to the confluence with the Green River near the Utah border, for four endangered native species in the upper Colorado River basin (humpback chub, bonytail, Colorado pikeminnow, and razorback sucker; Roehm 2004). The Recovery Program managers negotiate reservoir releases for instream flow (ISF) with water managers to protect riparian environments and fish spawning habitats (Speas et al 2014), remove and inhibit nonnative species in the stretch (Breton et al 2014;Zelasko et al 2015), construct and maintain fish passages (Roehm 2004), reintroduce endangered fish into historic habitats (Zelasko et al 2011), and monitor and assess endangered fish and their habitats (Bestgen et al 2012). …”

Survival and growth rates of stocked razorback suckers (Xyrauchen texanus) in a wetland of the Green River, Utah

“…To bolster populations, the Upper Colorado River Endangered Fish Recovery Program initiated an aggressive stocking plan in 1995 that continues today (Nesler et al, 2003;Zelasko et al, 2010). Since 1995, over 200,000 razorback suckers have been stocked.…”

“…Since 1995, over 200,000 razorback suckers have been stocked. From 1995-2005, fish were stocked at various sizes, but small fish <300 mm total length (TL) did not survive well and now hatcheries try to stock all fish >300 mm TL (Zelasko et al, 2010). Hatchery augmentation appears to have helped increase adult abundance in the upper Colorado River Basin.…”