Bottcher, J.L., T.E. Walsworth, G.P. Thiede, P. Budy, and D. Speas. 2013. Frequent Usage of Tributaries by the Endangered Fishes of the Upper Colorado River Basin: Observations from the San Rafael River, Utah. North American Journal of Fisheries Management, Management Brief. Online DOI: 10.1080/02755947.2013.785993.
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, oftenmoving
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.