Safety of AQUI‐S 20E (10% Eugenol) as a Sedative for Freshwater Fish

Abstract

AQUI-S 20E (10% eugenol) has been shown to be an effective fish sedative for freshwater finfish, but to be approved for use in the United States, the U.S. Food and Drug Administration must be provided with data demonstrating the product is safe to treated animals. Accordingly, we evaluated the safety of AQUI-S 20E when used to sedate Rainbow Trout Oncorhynchus mykiss, Yellow Perch Perca flavescens, and Channel Catfish Ictalurus punctatus. After identifying the highest effective concentrations likely to be used by fisheries biologists to sedate each species to handleable, replicate groups of fish were exposed to this intended concentration (1×) or a 50% higher eugenol concentration (1.5×) for periods of time adequate to effectively sedate 80% of fish to handleable (ET80) or for predetermined treatment periods exceeding the ET80. These predetermined treatment doses (40 and 60 mg eugenol/L for Rainbow Trout, 80 and 120 mg eugenol/L for Yellow Perch, and 100 and 150 mg eugenol/L for Channel Catfish), treatment periods (2.25-8.75 min for Rainbow Trout, 4.0-10.5 min for Yellow Perch, and 2.5-12.0 min for Channel Catfish; specific treatment periods depending on doses), and ET80 values were used to establish margins of safety for each species. An adequate margin of safety was defined as treatment periods ≥ 3-4 min longer than the 1× ET80 and ≥ 2-3 min longer than 1.5× ET80 after which fish survival was ≥ 95%. Based on survival, there was an adequate margin of safety associated with overexposing fish to AQUI-S 20E. Given the absence of biologically relevant effects of AQUI-S 20E exposure on tissue histology, there is no evidence to suggest that the survival-based margins of safety should be revised to be more conservative. Our results indicate there is an adequate margin of safety associated with the use of AQUI-S 20E to sedate freshwater fish to handleable.

Effective Anesthetic Dosage and Recovery from Specialized Surgical Methods in Shortnose Gar

“…Species that depend primarily or entirely on dissolved oxygen in the water are known to have shorter induction rates compared with air-breathing species (Hseu et al 1997;Neiffer and Stamper 2009), further supporting the conclusion that air breathing must be prevented when attempting sedation via immersion in gar. The dose of AQUI-S 20E required to induce stage 5 anesthesia in Shortnose Gar in our study was lower than that reported for Rainbow Trout, Yellow Perch, and Channel Catfish Ictalurus punctatus (Bowker et al 2017), while induction times were longer compared with other sedatives tested on other species (Bridger and Booth 2003;Ammann et al 2013;Wargo Rub et al 2014;Midwood et al 2018). In addition, recovery time was quick and comparable to other species that have been sedated using AQUI-S 20E (Javahery and Moradlu 2012), and we did not observe adverse reactions, such as prolonged recovery from sedation or short-term mortality.…”

“…One major benefit of AQUI‐S 20E is that wild‐caught fish can be immediately released after treatment (https://www.fws.gov/fisheries/aadap/inads/AQUI-S20E-INAD-11-741.html), permitting its use in field studies. AQUI‐S 20E has been shown to effectively sedate a wide variety of fishes to a “handleable” state (Bowker et al 2015, 2017); however, the effective dosage of AQUI‐S 20E for achieving stage 5 anesthesia (Summerfelt and Smith 1990) specifically in gars is unknown.…”

A meta‐analytic review of monoterpene for fish anaesthesia

“…As such, different countries have officially licensed eugenol as an aquatic anaesthetic with no withdrawal time (MCC (Medicines Control Council, South Africa), 2004; MPI (Ministry for Primary Industries of New Zealand), 2022) or with a withdrawal period set at 7 days (MAFF (Ministry of Agriculture, Forestry and Fisheries of Japan), 2015) although this compound is not currently FDA‐approved (FDA (Food and Drug Administration, United States of America), 2007) and no information could be found in European agencies. Yet, although other monoterpenes require further investigation, it is noteworthy that MS‐222 recommended withdrawal period varies from 21 (Bowker et al, 2019; FDA (Food and Drug Administration, United States of America), 2007) to 70 days (AQUAVET SA, 2022). Furthermore, MS‐222 is considered a local anaesthetic that blocks voltage‐gated sodium channels and prevents the development of nerve action potentials while not paralysing fish muscles (Attili & Hughes, 2014).…”

Using Survival Models to Estimate Invertebrate Prey Identification Times in a Generalist Stream Fish

“…After subsequent time periods varying in length from 10 min to 31 h postfeeding, we used gastric lavage to recover the remaining prey items. This involved the use of Aqui-S (Bowker et al 2017) as an anesthetizing agent and the use of a 60-cm 3 syringe fitted with a blunt, 18-gauge needle. Water was syringed into the stomach of each fish, and prey items were collected into a tray, filtered through a coffee filter (Melitta brand), and preserved in ethanol for inspection under a dissecting microscope.…”