Effectiveness of Two Potential Immediate-Release Compounds (AQUI-S20E and BENZOAK) to Sedate a Variety of Finfish to Handleable

Availability of safe and effective fish sedatives or anesthetics is crucial to fisheries researchers.  Fisheries professionals routinely sedate or anesthetize fish for procedures such as collection of samples or morphometric data, surgical implantation, and transport.  Ideally, a fish sedative is safe, effective, and easy to administer; has rapid induction and recovery times; can be used over a range of water chemistries, and is inexpensive.  Additionally, it is often desirable that the sedative have no withdrawal period so that after sedation, fish can be immediately released into the wild or taken to market.  Currently, there are few sedative options available to fisheries professionals, and there is no sedative that can be legally used as an immediate-release sedative.  Only the tricaine methanesulfonate products (MS-222) are approved by the U. S. Food and Drug Administration (FDA), but their use is restricted to four families of fish, use at water temperatures above 10C, and a 21-d withdrawal period is required for fish intended for human consumption or that may be caught and consumed.  For many applications, holding fish post-sedation is not practical in field settings and can seriously compromise the objectives of management or research activities.  To avoid these complications, an approved immediate-release sedative is desperately needed.

AQUI-S20E (10% eugenol) and Benzoak (20% benzocaine) are two potential immediate-release fish sedatives that have been shown to be safe and effective, but are not approved for use in the U. S.  In an effort to gain FDA approval for these products, a series of trials were conducted to demonstrate that each was effective in sedating a variety of freshwater finfish species to handleable.  Fish species tested included rainbow, brown, and lake trout (salmonids), hybrid striped bass, channel and blue catfish (warmwater finfish), walleye, and yellow perch (coolwater finfish).  To demonstrate efficacy, groups of 30 fish were individually exposed to AQUI-S20E, Benzoak, or MS-222 at doses sufficient for fish to become sedated in ≤ 5 min.  At the doses tested, mean sedation times for each of the three temperature grouping of fish were ≤ 2.2 min and mean recovery times were ≤ 7.0 min. Studies conducted to compare sedation times between individual and groups of fish showed no consistent trend.  Results from these studies demonstrated that these two sedatives were effective in sedating a variety of finfish to handleable, and reports summarizing the studies have been submitted to FDA in support of their approval.