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Greater Seattle Aquarium Society

Title As You Wish: Euthanasia (Part 1)

by Heather Candelaria

One of the cardinal rules of science, when working with animals, is to try to remain objective and try not to anthropomorphize.

When observing animals, we tend to want to apply our own human sensibilities to their behavior and activities. Primarily we want to think that have emotions and feelings in the same way that we do.

We are human and we can empathize with the situation of a fish, and this can be a very useful tool. A single fish which would normally be found in a school can should seem lonely, fish in brightly lit bare tanks will look afraid, and fish that are growing and thriving are called happy.

These words are more of a convenience to convey a state of being than they are accurate, though. Fish do not get lonely, they do not fear, and they cannot be happy. Fish can behave as if they are feeling these things, but the fact of the matter is that fishes brains just do not have the complexity necessary to give rise to emotions without our help.

I think that the most complex and misunderstood emotion, or physiological state of being, is pain. Pain is pretty hard to pin down as an objective phenomenon, it tends to be subjective in nature, with very little physical proof other than the tendency we have to yell ouch when we stub our toe.

Pain is not a basic straight forward event, it is much more complex than I intend to go into right now, but the basic fact that is important to know is that pain generally occurs as a result of some sort of damage being done to the body or cells of an animal.

Pain evolved as a sort of warning system, to tell an organism that damage is occurring to its body and that evasive action is a good idea. Getting away from the source of the pain is therefore a very important drive directing all animals capable of feeling pain.

With this in mind, I would like to express my opinion about the humane and painless method of euthanizing a fish; the freezing method.

The method of freezing may not be the nice, pain and trauma-free, method that many people like to think it is. Freezing a fish to death may be trauma free for you, simply pop Mr. Bubbles in a box---out of sight and out of mind---until a few hours later when viola! Fish popsicle.

Unfortunately, while Mr. Bubbles may look like he died in peace, with no signs of a struggle, there are several ways to interpret this observation. A few of them are; a) the fish died quietly with no struggle and therefore no pain, b) the fish had no obvious pain causing stimulation that it was able to evade, and therefore it remained still until death occurred, c) the act of moving became a painful stimulation causing the fish to remain still during freezing.

In freezing to death, we humans get to experience some nice brain chemicals. Our complex brains have a few tricks that make pain and damage to our bodies much easier to bear. When experiencing great pain, we get a rush of endorphins, and when freezing we get put into a state of euphoria. As bad as freezing to death sounds, I’ve been told that as far as preferred methods of dying go, freezing is one of the most pleasant. Well, for mammals at least.

Mr. Bubbles doesn’t have a very complex brain, and he wouldn’t have the same experience of freezing that we would. Warm-blooded animals need to maintain a steady body temperature. When they cannot maintain their body heat, their health declines and the brain puts the chemical factory into over-time in an attempt to soften the blow of the trauma.

Since most fish commonly kept in aquaria are endothermic, they do not maintain a steady internal body temperature. Their body temperature is the same as the environment in which they find themselves.

When exactly does death occur when freezing a fish? I’m sure it occurs sometime after the fish starts to feel its body being damaged by the process. By the time the cellular walls are bursting I’m pretty sure that the fish has taken its last gasp, but a great deal of damage (pain) occurs before death does.

I think the best way to put a fish out of its misery is the fastest way possible. Dropping Mr. Bubbles into a blender is not the nicest (or cleanest) method of euthanasia, but as far as Mr. Bubbles is concerned, it is all over with before he has time to even notice. Unfortunately, while a fast death is best for the fish, our human sensibilities tend to get in the way and sudden deaths are generally violent, and we are not accustomed to committing violent acts towards our loving pets.

To be continued...?