FDA approves Merck’s AQUI-S E10% for field sedation of wild freshwater fish

The US Food and Drug Administration has approved Merck’s AQUI-S E10%, an eugenol immersion solution, for sedating wild freshwater finfish during field handling, marking a significant step for resource management practices.

Merck Animal Health said the US Food and Drug Administration has approved AQUI-S E10%, an eugenol immersion solution, for sedating freshwater finfish to a handleable condition in field settings.

According to the FDA, the decision was made on 25 August and is intended for wild fish populations rather than aquaculture, hatchery or aquarium use. The agency said the product is designed for resource-management work such as spawning, tagging, weighing and measuring, with treated fish able to be released once they have fully recovered. It also said the product is safe and effective when used as directed, and that residues in edible tissue are not expected to create a food-safety concern.

Merck said the product is a ready-to-use liquid formulated for direct addition to treatment tanks. The approved dose ranges from 25mg/l to 40mg/l for salmonids and from 40mg/l to 100mg/l for non-salmonids. The company said there is no withdrawal period when the label is followed.

Tim Kniffen, a Merck technical services veterinarian, said the product offers a practical option for sedating small numbers of fish in the field. Merck said AQUI-S E10% will be sold in 1-litre and 4-litre packs and is due to reach the market in the fourth quarter of 2026.