Documentation of spawning by Razorback Sucker, Xyrauchen texanus, Razorback Sucker in the lower Grand Canyon during 2014.

Authors: Judith M. Barkstedt, Adam L. Barkalow, Steven P. Platania, Ronald B. Kegerries, Brandon Albrecht, Brian D. Healy, James R. Stolberg, Mark C. McKinstry

Year: 2014 (xlvi)

Abstract

The Grand Canyon section of the Colorado River, from Glen Canyon Dam downstream to Pearce Ferry, supports federally endangered Gila cypha, Humpback Chub and Xyrauchen texanus, Razorback Sucker. Downstream of the Grand Canyon in Lake Mead, stable reproducing Razorback Sucker populations have been documented since 1996. Recent tracking of sonic-tagged adults and captures of larval Razorback Sucker by Bio-West in the Colorado River inflow of Lake Mead suggested this species might, at least seasonally, be expanding upstream of the lake and be using the lower Colorado River in the Grand Canyon. In 2014 a study was initiated to determine the distribution of adult, juvenile, and larval Razorback Sucker in the Grand Canyon. The 100-mile long study area for the 2014 larval fish survey in the lower Grand Canyon began near Lava Falls (RM 179.2) and extended downstream to Pearce Ferry, at the Colorado River inflow into Lake Mead (RM 280). This section of river is characterized by a narrow river corridor with limited floodplain development, gradients alternating between steep rapids and long pools and runs, and substrata ranging from silt to bedrock. A general randomized tessellation stratified (GRTS) design was used to generate fish sampling locations for this study. This technique ensures spatially balanced samples and a robust statistical design. The 40 sampling locations generated for this project were sampled monthly (n = 6) from April through September 2014. The 240 larval fish sites sampled in the lower Grand Canyon during 2014 yielded 10 species and was numerically dominated by catostomids (>80% of cumulative sample). Noteworthy was the collection of over 450 larval Razorback Sucker in the lower Grand Canyon at over 20 unique sites during April and May. Collection locations of larval Razorback Sucker ranged from RM 179.1 (upper end of the study area) downstream to RM 279.1 (our lowermost sampling site). The 2014 larval fish study documented spawning of Razorback Sucker in the Grand Canyon thereby expanding the breeding range of this endangered fish and is another positive step towards recovery for this species.

Resumen

Entra texto de resumen en español