Anesthesia and Euthanasia of Fish

Unit 004-021: Anesthesia and Euthanasia of Fish Using MS222


To describe the use of MS222 for both the anesthesia and euthanasia of fish.

Roles and Responsibilities

It is the responsibility of the principal investigator (PI), graduate student, or LACF staff to terminate fish at the request of the PI.

Materials Needed

  1. Gloves
  2. Safety glasses
  3. Face masks
  4. Small beaker
  5. Container with lid (marked “for MS222”)
  6. Prepared fish water
  7. MS222 (Tricaine: Sigma Cat. #A-5040, or Finquel Inc. Part No. C-FINQ-UE from Argent Chemical Laboratories, or comparable)

Applicable Locations

All facilities of the Charles River Campus LACF.

General Procedures

  1. Put on gloves, safety glasses, and face mask.
  2. Make a stock of MS222 to freeze:
    1. In a fume hood, dilute MS222 in DI water. Label as MS222 stock.
      1. 80mg tricaine powder
      2. 19.6ml DD water
      3. Adjust pH to ~7 using sodium bicarbonate as needed.
      4. Store this solution in the freezer in 5ml aliquots.

To Use as an Anesthetic

  1. Put on gloves, safety glasses, and face mask.
  2. Combine the following in a 250ml beaker:
    1. Thaw one vial of about 5ml of the MS222 stock solution.
    2. Mix into ~100ml clean tank water.
    3. Transfer fish to be anesthetized into this container.

To Use for Euthanasia

  1. Put on gloves, safety glasses, and face mask.
  2. Combine the following in a small beaker:
    1. Thaw one vial of about 5ml MS222 stock solution.
    2. About 10ml clean tank water.
  3. Fill a container (transfer container) with small amount of prepared fish water.
  4. Use a dedicated net (from the tank from which the fish are being taken) to capture fish to be euthanized.
  5. Transfer fish into the transfer container.
  6. Bring transfer container with fish in it into workroom.
  7. Drain as much water from container as possible. This will decrease the amount of MS222 needed by making the concentration higher.
  8. Pour the diluted MS222 solution into the container.
  9. Put lid on container.
  10. Fish should be dead within 15 minutes.
  11. Remove fish from the solution, bag the carcasses, and place in refrigerator. At the end of the day the bag is brought to the freezer in the main LACF.
  12. Empty container into sink drain and run water for two minutes.
  13. Disinfect container and beaker in bleach solution (1:10). Rinse thoroughly.

Record Keeping

Be sure to record on the day’s record. If an entire tank has been put down, note it on the census sheet as well, and keep the tank card on file in the office.

Note: These amounts are based on the fact that MS222 at 50–100mg/liter provides a deep anesthesia and 25–35mg/liter of MS222 provides a light anesthesia.