Evaluation of the Green River Canal fish screen: Survival & physical assessment of Razorback Sucker using an innovative tagging method

Authors: Cat Adams, Kevin Bestgen

Year: 2023

Abstract

Water diversions on rivers entrain substantial numbers of fish globally and are especially concerning when the species involved are rare and endangered. In the Upper Colorado River Basin, stationary Passive Integrated Transponder (PIT) tag antenna arrays detected entrainment of over a thousand native fish into the Green River Canal (GRC), Green River, UT between 2013-2018, including endangered Colorado Pikeminnow, Humpback Chub, Bonytail, and Razorback Sucker. In 2019, a fish weir and screen were installed at the canal entrance to reduce fish entrainment. This weir and screen structure was designed to return fish to the river via a return channel that can be accessed via flow through a bypass channel or over the screen, which reduced GRC entrainment by >99%. However, flows in the return channel, bypass channel, and over the screen are swift, turbulent and may cause mortality or physical damage. To investigate this, we released hatchery-reared Razorback Sucker (194 mm-450 mm TL) to assess their survival and condition before and after experimental releases through the bypass channel and over the screen; balloon tags facilitated timely post-release fish retrieval. Survival of fish recovered after passage through the bypass channel and over the screen was 100%. Razorback Sucker that traversed the bypass or the screen were only slightly more likely to sustain minor injuries than control fish. Moderate injuries on bypass and screen fish occurred at slightly higher rates than control fish but were rare overall; no severe injuries were noted. Also, smaller fish were more likely to sustain minor injuries than larger fish. High rates of Razorback Sucker GRC exclusion and survival post-passage, combined with low injury rates, indicated this design is effective, and may assist with fish conservation in the Green River and elsewhere.