Euthanasia (humane killing)

[cichlidwoman]

Just had to put down an old mate today and wanted to share with everyone the info I've found on euthanasing fish (humane killing).

After trawling through forums and vet sites I've found some info that will be news to some and old news to others, eitherway hopefully it will change the way we humanly dispose of fish in the future.

1) What are the best ways to euthanase fish?    
 An overdose of anaesthetic administered by your veterinarian is a recommended method of euthanasia. The Australian Veterinary Association also states that "severance of the spinal cord, either with a scalpel or by pithing, is recommended. Pithing is recommended for fish up to 10 cm in length."

However, taking your fish to the veterinarian is not always practical, so there are some humane methods of euthanasia that fish owners can use:

Stunning fish with a sharp blow to the head, followed by decapitation is a rapid, effective, humane way to euthanase a fish, as long as it is carried out competently.

Clove oil is used to anaesthetize fish and is fatal to fish at doses greater than ¼ ml per litre of water. Clove oil is used in beer brewing and can be purchased through home-brewing outlets. It is also an aromatherapy oil, so try specialty outlets where oils are sold. Keep in mind that clove oil is classified as hazardous and can be irritating to the skin and eyes, and can be harmful if swallowed.

Since fish are cold-blooded, the brain can continue to function for a long time even after the heart and lungs have ceased functioning. Therefore it is possible for fish to recover from deep anaesthesia even if they are apparently dead because they are not breathing and have no heart beat. It can be very difficult to determine if a fish is dead, therefore, once the fish is deeply anaesthetized by leaving it in the solution for a couple of hours, it is recommended to freeze the fish, decapitate it or administer a sharp blow to the head to ensure it does not recover from anaesthesia.

What are not acceptable methods of killing fish?    
 Flushing fish down the toilet into the sewerage system causes slow death by exposure to toxic chemicals and water conditions.

Freezing fish is also a slow way to die and is not considered humane since the fish is not rendered rapidly insensible to pain and distress.

Taking the fish out of the water to suffocate is also not an acceptable method of killing fish.


2) From the University of Washington Approved Animal Use Policies (Euthanasia of Fish Species):

"Because tropical fish species, (i.e. zebrafish, medaka, and platyfish), have minimal to no physiologic adaptation mechanism for adjusting to cold (4°C) water, cooling to 4°C should be considered an acceptable method of euthanasia since the rapid decrease in temperature from 26°C (or higher) to 4°C induces rapid loss of consciousness and is lethal to these species. Fish euthanized by this method should not come in direct contact with the ice, because this may cause thermal burns and induce pain, but rather the ice should be added to a lowered amount of water for a contact time of 20 minutes."
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[GTR73]

The last fish I euthanised, a 7" Venustus,  I used the "ice slush" method. Distressingly, I don't think I had enough ice to begin with and the poor thing died a very slow death. I added more ice but the Venustus kept going for a long, long time.  :(

[cichlidwoman]

I used the clove oil and it worked really well. It put the fish to sleep peacefully and then we put him in 4 degree water. A better end to his life for us all as it wasn't distressing. I just bought the clove bud oil from a health food store for $12 and used 1tsp per 4 litres of water.