Razorback Suckers in Upper Lake Powell, Utah: Preliminary results from an 11-week field study in 2014

Authors: Travis Francis, Brian A. Hines, Mark C. McKinstry, David W. Speas

Year: 2014 (xlvi)

Abstract

Recent studies on population characteristics of Razorback Sucker, Xyrauchen texanus in the San Juan Arm of Lake Powell (Utah) and in Lake Mead (Arizona/Nevada) prompted investigators to conduct a similar study in the mainstem Colorado River inflow area of Lake Powell, an area that falls largely outside critical habitat designations under the Endangered Species Act. Using a variety of techniques (electrofishing, netting, sonic telemetry), biologists sampled the Colorado River inflow area (lake miles [LM] 118 to 140) for 11 mostly consecutive weeks from April 14 through June 7, 2014. Over that time period, a total of 246 individual razorback suckers were captured (including 26 recaptures), of which 8.1% were of unknown origin (i.e., did not contain a PIT tag). The percentage of untagged fish from the Colorado River inflow area contrast sharply with that recorded in the San Juan Arm (~40%). Most individuals collected in the Colorado River arm originated from stocking events in Green River, UT. Ripe male and female fish were found in what appeared to be at least two distinct spawning aggregations near LM 134, and ripe individuals were also located further down lake later in the sampling season. In addition to razorback sucker, two Colorado Pikeminnow, Ptychocheilus lucius, four Bonytail, Gila elegans, and two Flannelmouth Sucker, Catostomus latipinnis were collected. Objectives for 2015 include expansion of adult reconnaissance sampling to include other inflow areas (Escalante and Dirty Devil rivers), refinement of netting techniques and increasing level of larval fish sampling effort.

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