Officially it isn't euthanising them but that is the effect it has. Basically, with morphine, they go to sleep and their organs slowly stop functioning. Don't know the whole medical part but once they start giving a patent morphine in the large doses to ease their pain, it's only a matter of time. I'm sure morphine would work on fish but I don't think it is something the average person could get their hands on.

I think for larger fish sedating them then severing the spinal cord is the best way to go.

Andy,

This is where you lose me. If the guy is publishing on his university web site -- that's not peer review. What matters is whether Rose's critique is reviewed by other scientists in the field before publication, Sneddon's work certainly was. So until Rose publishes his critique, I'm not swayed.

Now, the second issue is that he cites one particular definition. McDonalds cite a Big Mac and Fries as a healthy part of a balanced diet. Doesn't make it true. Again, by publishing *his* definition of pain in a peer-review journal, the scientific community gets to decide whether it's reasonable or not.

In short, James Rose contributes nothing more to the debate any more than my personal opinions do.

Cheers, Neale

Neale, Rose's work has been published. See " The Neurobehavioral nature of fishes and the question of awareness and pain" in Reviews in Fisheries Science Vol 10, 2002. It has at least sparked interest, too, since it has been cited 50 times (according to the database I use), that's a pretty good rate since 2002.

This forum interested me quite a bit, as we hate to see fish suffer in the tank and being bullied by the rest when they are dying.

Euthanasia is a very gruesome subject, but to my luck I found an old book in a library sale that gave 3 tips for the "most humane" methods of carrying out this awful act, although the book states there is no perfect way to do this. The book is "A Practical Guide to Keeping Healthy Fish" by Lance Jepson.

1) Overdose the fish with a recognised fish Anaesthetic such as MS222 or Benzocaine.
2) Deliver a quick severe trauma to the back of the skull using an angler's club or mallet for killing fish. This will stun the fish and then decapitation can take place.
3) Alka Seltzer. Place the fish in a minimal amount of water and add as many Alka Seltzer tablets as possible. The CO2 released, the book states, as the tablets fizz and disolve will aneathetise and eventually kill the fish.

The book states that there are 3 methods to be avoided at all costs.
1) Death by Hypothermia usually by placing the fish in the freezer. This applies especially to temperate and cold water fish especially that are designed to endure low temperature.
2) Flushing down the toilet. Out of sight and out of mind, but it will not solve any welfare problems.
3) Never do nothing.

I hope this offers some tips as it is the most disturbing part of fishkeeping watching your fish suffer and what to do.

For me, i've never had to euthanise large fish, the only fish i've ever had to euthanise are fish like neons, guppys, platys and a molly once etc- basically small fish.

I have always found that putting the fish in a freezing bowl of water is a humane form of euthanasia (i.e. fish does not appear to suffer much, and dies very quickly, within seconds) and has always worked with 100% success for me.

This is the way i go about it;

a. Put plastic/ceramic/glass etc bowl with about 2-3inches of water in it in freezer.
b. Allow water to freeze enough to form a thin layer of ice completely covering the surface of the water.
c. Take bowl out of freezer and break the ice on the surface of the water.
d. Net sick fish and put it in bowl of water and watch it and wait for it to die.
e. Remove dead fish and wrap it in tissue paper and then dispose of it (bury it or put it in bin etc).


I've had to ethunise many fish during the years i have been fishkeeping, most of the fish i have had to euthanise were during certain moments in my fishkeeping experience, mostly during when i had a couple of outbreaks of fish tb and NTD (both untreatable and lethal/nasty fish diseases).
I've also had to euthanise fish dying from old age, like my old female molly, when she reached the grand old molly age of just over 4years old (the maximum average life expectancy for mollys), her health went down hill a lot, she gradually stopped eating and being active and ended up getting a swimbladder problem in the last week or so of her life as she lost a lot of body weight. I knew that she wasn't going to get better and her body wasn't coping anymore due to her age, so i euthanised her with the freezing water method when i knew she was in a bad way and was not going to get better. She died very quickly with this method.


So i would say i'm very experienced with the freezing water method of euthanasia on small fish. I've watched small tropical fish die with this method each time i've used it- what happens is that the fish hovers in the water for a few moments, then dashes around once or twice and then dies seconds after that. I watch the fish for fin, mouth and gill movements. Even though i know the fish is dead (its never taken more than about 20 or so seconds tops for fish to die with this method for me, i define "dead" being when the fish is no longer breathing or moving), i leave it in the water for a further minute or so to make sure there is absolutely no chance of the fish revieving.


You are never really going to be able to kill the fish absolutely instantainously, neither can you do the same with human beings. With human beings, i have read stories that when humans have been decapitated, it can take minutes before the brain is well and truly dead.
I think the fish dying in 30 seconds or less with the fish displaying little signs of stress or pain is a sign of a humane death.



The freezing method is always going to work best on small tropical fish. On sub-tropical or coldwater fish, it probably wouldn't work as well, and certainly not on fish larger than 3inches long.
My question, is that what are the most humane methods of euthanisa on large fish (particularly tough ones like large plecos)? I hate to think about anything bad happening to any of my plecos, but what if (imaginary scenario) one of my large plecos contracted an lethal and untreatable and nasty disease and had to be euthanised, what would you people do in such a situation? There are plenty of forms of euthanisia that work very well on small tropical fish, but not that many good methods for large ones.

This post has been edited by Tokis-Phoenix: Aug 20 2007, 02:38 PM

With bigger fish it seems to be that the more 'brutal' methods are best- hard whack on the head then destroy the brain, for instance. People use clove oil plenty too, but that's up for debate.

What is NTD? Oh, wait, neon tetra disease.

I recommend (from my very limited experience) the CO2 method via Alka Seltzer. I've needed to use it only twice, and both times the fish expired quickly with no signs of distress.

But to be fair, if two Betta Splendens have been fighting and one is ripped to shreads, you can see they are in pain

I also have had "good" experience with the freezing water method for my tropical fish. i've used it at least twice, once for a boesemani rainbow and once for a crowntail betta. both died within 20 seconds, however, i wouldn't say it looks pretty! the fish seem to suffer in my opinion for those 10 seconds out of the 20 that they are freaking out and trying to get out. then they die...humane? it's the best way i know how to go about it...but it's still heart-wrenching!

does noone here know a vet that could give some insight?

Well there was Emmsy... but we all know what happened there.

This is my personal observation, and I have no evidence to back it because I don't have time to go through all of the scientific papers. So maybe it doesn't belong in the scientific section but I thought I'd throw it on the table for debate because it's an interesting point.

A lot of people have said or suggested that for euthanasia to be humane it has to induce unconsciousness almost immediately. This implies that clove oil is not the most humane method because it does not do this. However I have been using clove oil for this purpose for over a year and I have not seen any signs of distress or suffering in fish once they have been placed in the clove oil solution but before they become unconscious. If the fish remains conscious in the clove oil solution for 30 seconds or so - but does not experience any pain and distress during this time - is there any reason why this should be considered inhumane? I see none. After this time the fish becomes unconscious. I usually just leave it in the solution until it stops breathing, because it seems unnecessary and a bit gory to take it out and decapitate it.

Further to my defence of clove oil as a euthanasia option for small fish, I quote from the study provided in the first post, American Veterinary Medical Association's Guidelines on Euthanasia.

"In evaluating methods of euthanasia, the panel used the following criteria: (1) ability to induce loss of consciousness and death without causing pain, distress, anxiety, or apprehension; (2) time required to induce loss of consciousness; (3) reliability; (4) safety of personnel; (5) irreversibility; (6) compatibility with requirement and purpose; (7) emotional effect on observers or operators; (8) compatibility with subsequent evaluation, examination, or use of tissue; (9) drug availability and human abuse potential; (10) compatibility with species, age, and health status; (11) ability to maintain equipment in proper working order; and (12) safety for predators/scavengers should the carcass be consumed."

(1) I answered this in my previous post. It is by no means proven but I have not noticed any signs that the fish becomes distressed. I have never observed darting, rapid gill movement, eye rolling, eratic fin movement or jumping in fish that have been placed in a clove oil solution for anaesthesia or euthanasia. Basically I believe it is reasonable to assume that clove oil does not cause pain or distress because for the first few seconds the fish would be perfectly capable of panicking, and they do not.

(2) This is the possible contention point. If enough clove oil is used it can render a fish completely insensible in under 10 seconds. Obviously this overdose is not safe for anaesthesia, but it is euthanasia that is being debated in this thread.

(3) If the fish is left in the clove oil solution until all gill movement has stopped and then left for another 5 minutes, I have never had one revive. I have never had a fish fail to become unconscious under clove oil.

(4) Clove oil is a poison and must be treated as such. However, fishkeepers handle similar quantities of more dangerous substances (ie. reagents for water tests - phenol!!!) on a daily basis and are used to being careful with small bottles.

(5) An overdose of clove oil is sufficient to render a fish unconscious and then over several minutes stop all gill movement. If a fish is not breathing and has not been breathing for five minutes, I think it's fair to say that fish is dead. Clove oil is reversible; this is clearly demonstrated by its use as an anaesthetic. So is halothane, isoflurane, most other inhalant anaesthetics, certain doses of barbiturates and many of the other methods suggested by AVMA. If used correctly and in sufficient dosage they are still considered humane methods of euthanasia.

(6) The requirement and purpose is to kill a fish with minimal pain and suffering. I believe that clove oil does this. It is easier for most people to place a fish into a solution than to hold down a struggling fish and try to cut in the right place so as to kill it instantly. If the fish is sedated before having its spinal cord severed or its brain pierced, what sedative will most people use? Clove oil. The majority of us, who are not doctors or vets and do not have access to restricted drugs, consider clove oil to be a humane and rapid way of anaesthetising a fish. If it was not, would it still be widely recommended? No. It would have been condemned by animal protection authorities - AND veterinary societies. I have seen that clove oil, even at anaesthesia concentrations, will kill a fish that is left in it for an extended period. However I would suggest that this method is less suitable for large fish because of the time needed to induce anaesthesia and the volume of clove oil that would be needed to treat enough water so that the fish remains comfortable in this time.

(7) I believe that an anaesthetic overdose is the least emotionally difficult on the fishkeeper who is having to destroy a friend. There's no blood, no gore, no struggling fish to pin down and butcher and no panicked last moments thrashing around in freezing or boiling water or a solution of some toxic poison. Clove oil is the only anaesthetic that is easily accessible to somebody without medical qualifications.

(8) In the majority of cases, clove oil is being used for the euthanasia of an old, injured or diseased fish kept by a hobbyist. That is the use this thread is mainly about. An interested hobbyist may perform a physical post mortem. However it is unlikely that any of the tissues would have to be collected and analysed for post mortem testing. If so, clove oil may be unsuitable but this will be the case in such a small minority of cases I hardly consider it worth worrying about.

(9) Clove oil is sold over the counter at pharmacies. This means it is easily available to any person. It also suggests that it cannot be abused by humans or it would not be so freely available. It is cheap as well.

(10) Obviously you would not be euthanising a fully grown barramundi (an enormous Australian angling fish) with a few drops of clove oil. I think this calls for common sense.

(11) Provided the clove oil is not sixteen years old and the container used is large enough for the fish to be comfortable in it, I don't see that there is much chance of the fish suffering because of poorly maintained equipment.

(12) I dispose of my dead fish by burying them and I have noticed that the graves of fish euthanised with clove oil have not been dotted with ant burrows. However I do not believe that a small tropical fish would retain sufficient quantities of clove oil in its body to poison anything that might eat it. The smell of clove oil may be enough of a deterrent in itself to discourage scavengers from eating dead fish anyway. Fish that are flushed down the toilet when dead or put in the garbage do not pose a threat to predators.



I believe that answers all the guidelines.

For the sake of correctness the guidelines do say that clove oil is unacceptable, but the reason given is insufficient research.

2x = 8.
x = 4.

I haven't proven that x = 4 because I haven't put it through a calculator etc. Just because I haven't researched every last possibility to prove that x = 4, doesn't mean that x doesn't equal four.

People have talked about cold / freezing water which can take a long time for the fish to die.

Has anyone tried a compressed air duster? If you turn the can upside down and spray you get tetrafluoroethane liquid that is chilled to approximately -27*C. I would imagine that would be much quicker than water chilled to 1 or 2*C

This post has been edited by maximinimus: Aug 11 2008, 11:57 AM

interesting debate, & until more research is done it will remain just that.

Some thoughts:-

Pain/pain response.... the debate as to whether animals feel pain is a typical anthropogenic one... ie we try to equate stimuli & response mode to a human stimuli/response mode, carried to even a basic logical conclusion there is no way to show any creature other than man "feels pain", as , as has already been said "they cannot tell us it really hurt". As a guide I would say that if a response to a stimulus produces a result analogous to a pain response in humans than the animal can be said to respond to "pain". At the end of the day I think it can be argued that humans merely react to unpleasant or potentially harmful stimuli in a way we call "pain response" and that it is inseparable from a similar action in other animals ( any that would react in a predictable way to a given stimulus). Just because we can give it a name and communicate that to other humans is by no means a scientific method of differentiation, as we are totally unaware if other animals can effectively communicate similar information, just because they cannot communicate such info to US does not mean that it does not happen. (OK a slightly wider application than just fish here)

Research to date:- Almost all research done in aquatics, and especially in medications etc are carried out on commercial fish.(after all that is where the money is) Therefore they are usually much larger and predominantly cold water species. It does not follow that such research is applicable to much smaller and tropical species. However it can be used as a baseline for further investigation. When it comes to tropical species held in captivity it is likely that most "useful" info will come from serious hobbyists and commercial breeders rather than scientific institutions..... AFAIK there is no "Rockefeller guppy institute", or similar conducting extensive and in depth research into ornamental tropical species. Commercial fish farms may commission research into specific problems, but IME this seems to be more a case of " get a vet & try to fix it", rather than a stricter sense of scientific research. The findings of such an investigation are no less valid for not being published or reviewed, but also should not be treated as "fact" until verified.

Clove oil as an anaesthetic:- used by US fisheries for documented investigations into non food species. Also used worldwide as a widely available "non vet" anaesthetic, used in several proprietary medications for this purpose.

Clove oil for euthanasia:- the attached report seems to indicate it's unacceptability based on lack of research or available verifiable data. Such research is unlikely to be forthcoming as clove oil is not a protectable ingredient under patent or copyright, and therefore there is no commercial gain to be made by further research. Products such as MS222 are commercially viable as the product can and is patentable and protected by the manufacturer, therefore commercial research is also viable.

My experience in euthanising fish from 1/2 to 16" is that both ms222 and eugenol (clove oil) are equally effective. as clove oil is easily obtainable I will restrict further comments to that product alone. Fish exhibit no "stress response" ... trying to escape, thrashing round, rapid movement or breathing... at sub lethal and lethal doses. Fish subject to sub lethal dose recover rapidly in clean water and exhibit no signs of ordeal following the useage, I have found no long term problems in its use as a calming agent or anaesthetic, lifespan does not seem influenced. (please bear in mind the objective nature o