Insights into managing wetlands as nursery habitat for endangered Razorback Sucker, Xyrauchen texanus, after three years of success at Stewart Lake, middle Green River, Utah

Authors: Robert* Schelly, Matthew Breen

Year: 2015 (xlvii)

Abstract

Endangered Razorback Sucker, Xyrauchen texanus, have declined in the Colorado River Basin as impoundment-related flow alteration has reduced access to off-channel wetland habitats and nonnative species have proliferated. For decades, survival of wild-spawned razorback suckers to juvenile stages has been negligible, and populations have been maintained by stocking of hatchery-raised fish. Since 2013, however, the management of Stewart Lake, a gated wetland on the middle Green River near Jensen, Utah, has served as a promising model for the re-coupling of larval Razorback Suckers with productive off-channel wetland nursery habitat. In a cooperative multi-year effort by Federal and State agencies called the Larval Trigger Study Plan, light trapping is being used to detect the presence of larval razorback suckers in the river, triggering increased releases from Flaming Gorge Reservoir, temporally matching peak flows to the period of larval drift. In 2013 and 2014, after two and three months of entrainment, respectively, many hundreds of juvenile Razorback Suckers were returned to the Green River. After a mild winter and the earliest larval emergence on record, the 2015 cohort of Stewart Lake Razorback Suckers was smaller than expected, but a number of age-1 fish spawned in 2014 were recaptured throughout the 2015 season, confirming successful recruitment. Here we examine possible factors driving the inter-annual variation in Stewart Lake Razorback Sucker cohort size, with an eye towards fine-tuning our management strategy to maximize Razorback Sucker survival and further disadvantage nonnative fishes.