Why we use Anaesthetics in aquatic animals:

  • The main uses include: immobilization of fish (for tagging), weighing, measuring, grading, collection of blood and transportation
  • Anaesthetics also provide relaxation and freedom from the reflex response
  • For general use in finfish during painful or stressful situations

Ideal anaesthetic characteristics:

  • Fast acting: 1-15 minutes
  • Renders fish insensitive to pain
  • Provides immobilisation and muscle relaxation
  • Easily administered with a wide range between safe and lethal dose
  • Quick recovery (up to 5 minutes)
  • Stable, biodegradable, non-toxic to humans
  • Cheap and long shelf-life

Administration of anaesthetics in water:

In order to administer fish anaesthetics, fish should be taken off feed for at least 12-24 hours beforehand. The lowest dose and exposure time of anaesthetic should always be used. The fish should then be monitored for at least 24 hours for any signs of stress (delayed) or mortality. The most common chemical anaesthetics include; MTS powder (Tricaine methane sulphonate or MS 222), Benzocaine and AQUI-S.