Frequent Usage of Tributaries by the Endangered Fishes of the Upper Colorado River Basin: Observations from the San Rafael River, Utah

Abstract

The importance of main-stem rivers and major tributaries to endangered Colorado River fishes is well documented, but the use and significance of small tributary streams remains poorly understood. Historically, these fishes probably used smaller tributaries for spawning, rearing, feeding, and refuge. Currently, the proliferation of nonnative species and altered flows may have affected tributary use by endangered fishes. In February 2008 and 2009, we installed a PIT-tag passive interrogation array (PIA) in the San Rafael River, Utah, approximately 2 km upstream from the confluence with the Green River, and another PIA approximately 60 km upstream from the Green River confluence. Using passive detections and active captures in the San Rafael River from 2008 to 2010, we detected 15 Colorado Pikeminnow Ptychocheilus lucius, 16 Bonytails Gila elegans, 20 Razorback Suckers Xyrauchen texanus, and five “undocumented” fish. Several endangered fishes were detected on multiple occasions and across years, often moving into and out of the San Rafael River from distances up to 360 km away (range, 6–360 km). Our findings demonstrate the use and the potential importance of small tributaries and their fragile habitats to endangered fishes.

Received May 13, 2012; accepted March 10, 2013

ACKNOWLEDGMENTS

We thank Krissy Wilson (UDWR) and three anonymous reviewers for their thoughtful comments provided on previous drafts of this manuscript. Peter MacKinnon designed, set up, and maintained the PIA systems. Craig Walker and Kenny Breidinger provided support and advice. Wally Macfarlane and Nira Salant provided GIS assistance and computed hydrogeomorphic statistics. We thank the many technicians who assisted this project in the field and laboratory. This research was funded by the U.S. Bureau of Reclamation, Conservation Activities for Sensitive Non-Game Native Fish Activities to Avoid Jeopardy Program, a S.E. and Jessie E. Quinney Fellowship, and the Ecology Center at Utah State University. Additional support was provided by the Utah Division of Wildlife Resources, the U.S. Bureau of Land Management, and the U.S. Geological Survey, Utah Cooperative Fish and Wildlife Research Unit at Utah State University (in-kind support). This study was performed under the auspices of Utah State University's IACUC protocol number 1310. Mention of brand names in this manuscript does not imply endorsement by the U.S. Government.