Euthanasia Of Freshwater Fish

[steelhealr]

One of the hottest questions on our forum is what is the safest, most humane method to euthanize an ailing fish. Classically, a preponderance of members will cite oil of cloves. Is there enough evidence to prove this method is the best? Below is a link to the current recommendations by the American Veterinary Medical Association (AVMA). Refer to page 20

AVMA Guidelines on Euthanasia

 

[andywg]

I think that possibly the swiftest method (especially on larger fish) is to decapitate and then pierce the brain, but many people (myself included) are not entirely happy performing such a gruesome procedure.

I recall some (possibly you) suggesting ice cold water for small fish, and I have used this with some "success" in that the fish rapidly stopped moving and then shortly after passed away. The reasoning behind this being that extreme cold is somewhat of an anaesthetic and it quite swiftly shuts down the fish's functions.

I am intrigued by the CO2 one, and whether it would have to be in a sealed environment to prevent the CO2 just off-gassing.

 

[-germ-]

Just thought i'd add, for the benefit of those that will be going into this subject scientifically (not me, although i'm very interested in what will be said), that the use of Phenoxy-2-ethanol is fairly common for euthanization and as an anaesthetic amongst vetenarians.
While i'm not sure of its availability (in its pure form) it is present in a great deal of aquarium medications (particularly bactericides).

Just thought it may be worth looking into on this thread

 

[steelhealr]

I believe the real question here is, as I have heard from Bignose, whether or not fish feel pain and I see no problem with this discussion leaning into that realm. To start, I believe we have to think about several issues here:

• pain
• depth of anesthesia, i.e., not having a painfree fish that is CONSCIOUS (level of anesthesia)
• level of pain relief

I do not believe that there are any studies on the specific use of oil of cloves, whose classic use is as a topical anesthetic. This was seen most graphically in the movie Marathon Man. I am not convinced that immersion of fish in oil of cloves brings on a level of unconsciousness rapidly, but, I am searching for any scientific studies on this.

SH

 

[Puffdaddy]

Steelhealr there has been a study on a species of salmon and the effects of clove oil. The effects of clove oil is directly related to the amount of clove oil used and the size of the fish. Larger fish taking longer to adhere to the effects. It is also stated that at a concentration of 140mg/liter fish are rendered unconscious immediately. Here is the link to the study that was performed.Clove oil research

 

[Fella]

I believe the real question here is, as I have heard from Bignose, whether or not fish feel pain and I see no problem with this discussion leaning into that realm.

Dr L Sneddon at the university of liverpool completed a study which she considers to prove fish do feel pain. I don't have the name of the study but it involved rainbow trout and using venom from a bee sting.

http/www.wellcome.ac.uk/en/pain/microsite/culture2.html

The link has more detail, but I can't find the name of the particular study.

 

[Bignose]

I believe the real question here is, as I have heard from Bignose, whether or not fish feel pain and I see no problem with this discussion leaning into that realm.

Dr L Sneddon at the university of liverpool completed a study which she considers to prove fish do feel pain. I don't have the name of the study but it involved rainbow trout and using venom from a bee sting.

http/www.wellcome.ac.uk/en/pain/microsite/culture2.html

The link has more detail, but I can't find the name of the particular study.

Ok, then, here's a good welcome to the scientific section. Fella, whether the word I bolded (prove) in your quote was your word or Dr. Sneddon's, it is an exceptionally poor choice to use in the scientific section. Unless the fish actually came out of the tank and told Dr. Sneddon that they felt pain, nothing has been proven. Now, correct phrasing here would have been "shows strong evidence that fish feel pain" or "shows that it is likely or very likely that fish feel pain" or something similar. But, no good and honest scientist can claim that research like this proves anything.

 

[Aphotic Phoenix]

I am intrigued by the CO2 one, and whether it would have to be in a sealed environment to prevent the CO2 just off-gassing.

The University of Washingtons Policy for the Euthanasia of Fish Species - 2002 describes the methods of using CO2:

Exposure to a solution saturated with carbon dioxide (CO2): When possible, carbon dioxide should be used from a compressed gas cylinder source. However, neither the 1993 nor the 2000 Report of the AVMA Panel on Euthanasia address the issue of the source/production of carbon dioxide as it relates to aquatic animal species. The use of chemical methods for the production of carbon dioxide, such as a saturated solution of sodium bicarbonate or Alka-Seltzer ®, has been proven quite effective with fish as noted in the literature. When dosed adequately sodium bicarbonate renders rapid loss of consciousness and death (4,6). As a result, the use of carbon dioxide liberated by chemical means will also be acceptable for the euthanasia of fish when compressed carbon dioxide gas cylinders cannot be used. Individuals who have demonstrated competency with this technique to qualified personnel (i.e. aquatic animal veterinarian or his/her designate) should perform the euthanasia of fish by carbon dioxide.

Sodium bicarbonate dosage: (30g/L or 120g/gallon)

Alka-seltzer ® dosage: (1 tablet/ 20L or 2 tablets/ 10gallons) Note: Fish euthanized with sodium bicarbonate or Alka-Seltzer® should not be used for human consumption.

Protocol: Fish should be placed into a container with an appropriate volume of water that will provide free movement of fish to be euthanized. Water should then be saturated with carbon dioxide from either a compressed gas cylinder (via the use of an air stone with a moderate flow rate for ~5-10 minutes) or by dissolving enough sodium bicarbonate or Alka-Seltzer ® into the water (via the dosages previously provided). Fish should be removed only after ten minutes have passed since their last observed opercular movements (respiration) have occurred.

Full Article Here

 

[Miss Wiggle]

I've always thought whichever method is quickest is best, to be frank about it dying is unlikely to ever be a nice experience for the fish however it happens, best to get it dead as quickly as possible and therefore shorten any suffering it feels. But this does also bring you round to the issue of weather fish do feel pain. If they are not feeling pain (or perhaps just not in the same way we do) then the time taken to die may be of no consequence?

for me it comes down to a slight conflict of interest all hobbyists will experience at some time, do you do what is best for the fish, or a compromise of what is best for you and the fish.

in an ideal world we would all always do what is best for the fish, however some of the methods of euthanasia considered to be best for the fish are really gruesome and enough to put a hobbyist off keeping fish for life. such as-

I think that possibly the swiftest method (especially on larger fish) is to decapitate and then pierce the brain, but many people (myself included) are not entirely happy performing such a gruesome procedure.

I certainly wouldn't want to do that to one of my babies, but if the hypothesis that the quickest method is the best is correct, then perhaps this is the best way to do it for the fish.

Does anyone know if there is a recommended veterinary practice for euthanasia and what it is? I assume if you have a vet who is willing to treat your fish if they are ill and the illness progresses to the point of needing to put them to sleep, you could probably take them to the vet and ask them to do it for you. Perhaps this is the best method as you take out the debate of what is best for you, the vet will be used to putting animals to sleep so while I'm sure it's not the favourite part of their job they may not be as distressed as you or I would at doing it, they are also a trained practitioner and whatever method they use should be able to do it skillfully so you take out the risk element or you making a mess of whatever method you try to employ and basically end up butchering your poor fish. I know it isn't a scientific method as have been discussed in this thread, but as a practical method for most aquarists it's certainly viable.

ok first post in the science forum, done. not much science but hopefully some discussion points to add to the topic.

 

[Fella]

I believe the real question here is, as I have heard from Bignose, whether or not fish feel pain and I see no problem with this discussion leaning into that realm.

Dr L Sneddon at the university of liverpool completed a study which she considers to prove fish do feel pain. I don't have the name of the study but it involved rainbow trout and using venom from a bee sting.

http/www.wellcome.ac.uk/en/pain/microsite/culture2.html

The link has more detail, but I can't find the name of the particular study.

Ok, then, here's a good welcome to the scientific section. Fella, whether the word I bolded (prove) in your quote was your word or Dr. Sneddon's, it is an exceptionally poor choice to use in the scientific section. Unless the fish actually came out of the tank and told Dr. Sneddon that they felt pain, nothing has been proven. Now, correct phrasing here would have been "shows strong evidence that fish feel pain" or "shows that it is likely or very likely that fish feel pain" or something similar. But, no good and honest scientist can claim that research like this proves anything.

While I understand what you're saying, and I don't want this section to get bogged down in use of terms and grammar, "She considers to prove fish do feel pain". Which is true, that is what she has considered with her study which provides evidence that it may be the case.

http/www.journals.royalsoc.ac.uk/content/e8vyfa4ndt5c4q0a/

Here is a small abstract from one of the studies.

 

[rdd1952]

For small fish like tetras, I use a method that is definitely quick and I should think as painless as possible. That is simply putting them in a sandwich bag, laying them on a brick and smashing with a brick. It is over instantly. It sounds gross but it works.

Edited to remove personal experience per forum rules.

 

[lljdma06]

For small fish like tetras, I use a method that is definitely quick and I should think as painless as possible. That is simply putting them in a sandwich bag, laying them on a brick and smashing with a brick. It is over instantly. It sounds gross but it works.

As for fish feeling pain, I strongly believe they do. Anyone who has ever fished and hooked a fish in a tough part of their mouth or even had one swallow a hook I'm sure has felt how the fish stiffens as you are trying to get the hook out. Sort of the way I feel I stiffen up when the dentist puts that drill in my mouth and starts trying to find oil. To me it seems to be a reflex they have. It may not be an indicator of pain but certainly would seem that way to me.

I'm not an expert on this subject, so I have no comments to make on it at all. I prefer to dwell on how to keep my fish alive rather than on the ethics and methods involved in killing them. I do think its a great topic, just not of particular interest to me. I am, however, am watching it closely as I want to see how arguements and debates are handled in scientific manner in this forum. Please remember SH's rules, so try to keep emotional appeals and conjecture based solely on experience out of this discussion. Please don't take offense rdd1952, but your post has them. The use of "anybody", "I should think", and "I strongly believe" actually weakens what could have been a potentially good arguement for your claim.

If you had simply stated that fish experience a stiffening response to external stimuli (hook in the mouth, you grabbing it, etc), and then proceeded to explain what could be the possible physical motivators for this stiffening response (chemical, electrical, etc), your arguement would have been much stronger, especially if you used evidence to back up your claim. I'm just pointing that out, so please don't take offense.

And in reference to Fella's issue regarding the use of "prove." It is acceptable if the word is used in the context of a direct quotation from a source, which from what I understand, Fella, it is how you interpretted it. However, if that is truely the context, then direct quotations are necessary. It would then prevent the generalization on your part, which invited Bignose's comment. With the use of direct quotations, Bignose is then able to comment on the actual quotation and its claim, and avoid any personal reference to you.

I apologize if I am bogging this thread with terms and grammar points, but I strongly urge people to read and reread SH post on how to argue. In addition, if people are really serious about argueing and debate, there is an excellent, albeit old book on rhetoric by Edward P. J. Corbett, Classical Rhetoric for the Modern Student. I highly recommend it.

I'll be quiet now, and continue to follow this discussion with interest. SH, if any of this post is objectional to you, please feel free to remove it or delete it. It is not quite on topic, I know, but it is necessary for this first dicussion to address these points so it doesn't have to be discussed in future debates. This is our first discussion, rough spots are going to appear.

llj

 

[andywg]

While we are in danger of drifting off euthanasia and into pain, I feel the below need answering:

While I understand what you're saying, and I don't want this section to get bogged down in use of terms and grammar, "She considers to prove fish do feel pain". Which is true, that is what she has considered with her study which provides evidence that it may be the case.

http/www.journals.royalsoc.ac.uk/content/e8vyfa4ndt5c4q0a/

Here is a small abstract from one of the studies.

Terminology is very important in a scientific debate. Many debates are clouded in popular media due to incorrect use of different terms. Proof is a very well defined word and in a scientific forum we will need to be somewhat sharp on incorrect usage of words which have a different meaning. The "It's only a theory" line used by ID people on evolution is a classic example of misusing a word to froard a debate.

As for fish feeling pain, I strongly believe they do. Anyone who has ever fished and hooked a fish in a tough part of their mouth or even had one swallow a hook I'm sure has felt how the fish stiffens as you are trying to get the hook out. Sort of the way I feel I stiffen up when the dentist puts that drill in my mouth and starts trying to find oil. To me it seems to be a reflex they have. It may not be an indicator of pain but certainly would seem that way to me.

Okay, the second quote and the research Fella is referring to are extremely debateable about truly supporting whether fish feel pain.

There is now little doubt that fish experience nociception, that is they have nociceptors that recognise harmful extermal stimuli and generate a response form the fish to them. However, the response is usually taking place in the spinal chord and not in the higher parts of the brain where this information is dealt with in mammals when experiencing pain. This an area of the brain not present in fish, that is why traditionally people have considered fish not to feel pain.

In response to Ms Sneddon, in a rebuff in this article the below is stated (my bold to emphasise the definition of pain):

James Rose, a fisherman and a professor in the University of Wyoming's Department of Zoology and Physiology, wrote a scathing critique of Sneddon's findings, which appeared on the university Web site, claiming that they contained poor methodology and misinterpreted the data. The key to his objections centered around how animals perceive pain. He cited the Seattle-based International Association for the Study of Pain, which defines pain as "an unpleasant sensory and emotional experience associated with actual or potential tissue damage..." And, he said, the signals sent by nociceptors are not in themselves pain.

This is the root of the problem with pain. For pain to be processed in a scientific definition of the word will require a completely different area of the nervous system in the fish to process the signals from the nociceptors and thus bring about a psychological reaction from the fish. I understand Ms Sneddon is undertaking further tests to try and prove that fish do feel pain in the scientific definition of the word. However, one piece of research proving that nociception takes place in fish does not prove that fish feel pain in any way shape or form.

It may well be that future research by Ms Sneddon, and others, shifts scientific opinion towards believing that fish do feel pain, but for now those claims just can't be made.

I myself am all for posts like llj's to remain as they will provide a support for the attempts to keep the forum scientific. I would sooner have posts like that remain than incorrect posts deleted and the same errors occur time and again.

 

[Aphotic Phoenix]

Well pain is an integral part of the debate, because of the tendency to associate pain with suffering. Why would there be any moral implication about "humane euthanasia" if there was no argument about the inability for fish to feel pain?

The article Can fish suffer?: perspectives on sentience, pain, fear and stress by K.P. Chandroo, I.J.H. Duncan, R.D. Moccia brings up several interesting points on this subject, such as this one detailing that fish may produce (and receive) pain suppressing chemicals.

In mammals, adrenocorticotropin may be released from the pituitary gland when
noxious stimuli are encountered (Chapman and Nakamura, 1999). Endogenous opioids
(morphine-like substances) are also produced in tetrapods, which can suppress the intensity
of pain experienced (Zieglgänsberger, 1986). A number of studies have shown that the nervous
systems of teleost fish also produce chemical compounds related to adrenocorticotropic
hormone and pain-mediating opiates (Ng and Chan, 1990; Vecino et al., 1992; Danielson
et al., 2001). Jansen and Green (1970) and Ehrensing et al. (1982) demonstrated that analgesia
could be achieved in goldfish (Carassius auratus) subjected to electric shocks by
adding morphine to the tank water. Similarly, Chervova (1997) found that it was possible to
modulate pain-induced behaviour of rainbow trout using opiate and non-opiate analgesics.
Using opiate antagonists, Ehrensing et al. (1982) found that morphine analgesia in goldfish
could be blocked through modes of action similar to those in tetrapods. In addition, it has
been reported that at least six different protein binding sites, which may act as receptors
for pain modulating molecules, are present in teleost fish (Stoskopf, 1994). In zebrafish
(Danio rerio), the distribution and type of opioid receptors in the CNS supports a sensory
or analgesic role for those receptors, and further suggests that some nociceptive pathways
have been conserved throughout vertebrate evolution (Porteros et al., 1999). Expression of

-opioid receptors in zebrafish has been localised to limbic structures, as well as to other
brain structures that have been implicated in pain mediation via ablation studies (Porteros
et al., 1999). Sneddon (2003), demonstrated a morphine-induced reduction in pain-related
behaviours as well as opercular beat rate in rainbow trout subjected to noxious stimuli. The
author concluded that morphine acts as an analgesic in trout, and that the potential exists
for both pain perception and response in fish that are not simply reflexive in nature.

And also points out slight differences in brain structure that are not yet fully understood...
In addition, the fish telencephalon may mediate sensory integration and executive
functions analogous to those of the tetrapod telencephalon. Such integrative or executive
functions of the fish telencephalon include the regulation of avoidance learning (Overmier
and Hollis, 1990), habituation (Rooney and Laming, 1988), general arousal and social behaviour
(Rooney and Laming, 1988; Overmier and Hollis, 1990; Riedel, 1998), as well as
motivation and emotional learning (Portavella et al., 2002). Since the telencephalon processes
somatosensory input and plays an integrative role in the avoidance responses of fish
to noxious stimuli, it is probable that nociceptive signals (as well as other senses) in fish are
not limited to initiating reflexes via the spinal cord or brainstem, but are also relayed to pallial
and sub-pallial structures. The mechanisms by which pallial, sub-pallial and other brain
regions generate consciousness, for any vertebrate animal, is the subject of intense debate
and a number of working hypotheses (Searle, 2000; Dehaene and Naccache, 2001; Dennett,
2001).

I am doubtful that I have managed to post the most relevant information from the article (since I'm still half asleep), but I did find it a most interesting read.

 

[Bignose]

That Chandroo et al. paper seems to be one of the more compelling. The gist of the paper, in one phrase, is that while fish's brains don't have the exact same form (and hence function) as higher species, the similarities are closer than has been previously acknowledged, and other parts of the brain may very well indeed be performing similar functions as the higher tetrapods. What we really need is a fish to sit still in an MRI machine while tests are performed on it.

If I get the time, I'll try to look up some of the more recent articles that cite that Chandroo paper.