A Field Test of Eugenol‐Based Anesthesia versus Fish Restraint in Migrating Adult Chinook Salmon and Steelhead

Abstract

Many studies require the collection and handling of fish, which may have short‐ and long‐term effects on their behavior and survival. We evaluated the effects of AQUI‐S 20E, a eugenol‐based anesthetic, on adult spring Chinook Salmon Oncorhynchus tshawytscha and winter steelhead O. mykiss in the Willamette River, Oregon. We experimentally compared the postrelease behaviors and movement into spawning tributaries of fish radio‐tagged under anesthesia with those of fish radio‐tagged while being manually held in a restraint device. Anesthetized Chinook Salmon were less likely than restrained Chinook Salmon to swim downstream (20% versus 47%), more likely to reascend the fishway at which they were collected (89% versus 60%), and more likely to escape to tributaries (82% versus 47%). The treatment effect persisted after statistically controlling for tag date, release time, and fish size. In contrast to Chinook Salmon, the percentages of anesthetized and restrained steelhead that moved downstream (17%), passed the dam (88–90%), and escaped to tributaries (79–83%) did not differ by handling treatment. Our results highlight that the effects of handling and tagging need to be evaluated, that such effects may be species specific and occur at multiple scales, and that eugenol‐based anesthetic should be used instead of restraining devices for Chinook Salmon. Received July 8, 2013; accepted January 29, 2014

Condition‐Dependent En Route Migration Mortality of Adult Chinook Salmon in the Willamette River Main Stem

“…The dam is located 41 river kilometers (rkm) upstream from the Willamette River-Columbia River confluence and~206 rkm from the Pacific Ocean (all subsequent river kilometers are from the ocean). The fishway and trap along with salmon capture, handling, and tagging methods were described by Caudill et al (2014). Briefly, adult Chinook Salmon were diverted from the fishway into a holding tank for processing throughout the runs (April-June) each year.…”

Thermal exposure of adult Chinook salmon in the Willamette River basin

“…Additional among-individual differences were attributable to passage times in the main stem Willamette, with some fish requiring several weeks to reach tributaries. Some appeared to delay migration near Willamette Falls, but it is unknown whether the delay was an artifact of fish capture and handling (e.g., Frank et al, 2009;Caudill et al, 2014), a response to environmental conditions, or due to some combination of factors. Regardless, behavioral differences among fish and differences in recapture timing had a much greater influence on total DDs than the date that salmon were collected at Willamette Falls.…”

“…1) capture and handling protocols, anesthesia, and intragastric tagging with uniquely-coded radio transmitters (model MCFT-3A; Lotek Wireless, Newmarket, Ontario) were described by Caudill et al (2014). All fish handling methods were approved by the University of Idaho Animal Care and Use Committee and permitted by the State of Oregon and the U.S. National Marine Fisheries Service.…”

“…Salmon were radio-tagged in approximate proportion to the annual runs, though the hatchery:wild composition of samples changed as study objectives evolved yearto-year (see Caudill et al (2014) for details). The radio-tagged samples included: 38 wild and 112 hatchery fish in 2011 (150 total), 311 wild and 189 hatchery fish in 2012 (500 total), and 70 wild and 229 hatchery fish in 2013 (299 total).…”

Coho Salmon Colonization of Oregon's Upper Willamette River Basin

“…Coverage extended beyond the expected distribution for Coho Salmon so as to monitor radio‐tagged Chinook Salmon and steelhead in related projects (e.g., Caudill et al. ; Keefer et al. ).…”