Exploring Fish Euthanasia
Some of the methods described in this article
are dangerous to life and limb and should not
be attempted by the incompetent - this
article is for information purposes only, and
as such no liability will be accepted for any
mishaps caused in the replication of the
descriptions.
Euthanasia n. an easy mode of death: the act
or practice of putting painlessly to death,
esp. in cases of incurable suffering.
(Chambers English Dictionary)
Having to kill a fish is something that most
of us do not relish - it's very different to
kill a fish that you have caught to eat than
it is to put an end to the life of a fish
that you have cared for over a period of
time.
Unfortunately fish get ill or injured, and
fish get old, sometimes in the process to
such a degree that their suffering becomes an
affront to us and we feel that something must
be. In the best case scenario fish just drop
dead, floating on the surface in the morning
having died peacefully in the night ( the way
that I image Forest Bump's fish might pass
away), more often than not, however, you
notice the fish becoming weaker and and in
difficulty as a process, such as death is.
This article cannot help you decide at what
stage to euthanize your fish, although fish
do feel pain it is entirely subjective - they
do have the same reactions to pain as we do,
but are incapable of expressing it; therefore
you should ensure their death is as painless
and sudden as you would wish your own. This
article looks at the most commonly used
methods and their impact on the fish before
it eventually dies. All fish should be given
a fair chance at recovery before the decision
is taken to kill it.
Each method will be looked at in relation to
the definition of euthanasia - and rated on
how much or little suffering the method will
cause on top of the underlying terminal
problem.
Flushing
This is the method coveted by the ignorant
and cowardly. A sick or injured fish is
flushed down the toilet to die in the
sewer.
I have heard justifications of this such as
"Once it's swirled about a bit, it'll be dead
anyway" - this is not true in any way. Fish
are aquatic animals and are generally used to
water current.
In the best case scenario the fish will die
from temperature shock quite quickly compared
to the prolonged suffocation and burning
caused by chlorinated water, cleaning
products and effluent.
This method should never be employed - out of
sight, out of mind does not equate to a
painless death.
This method is not recommended for any
fish.
Humane rating: 0% (if I could use a minus
figure I would)
Sudden blunt trauma
This is most commonly referred to as
"whacking with a hammer", or brick, or
angler's priest. The end result is the same -
crushing the fish's skull to kill it.
The method involves taking the fish out of
the aquarium, laying it against a sturdy
surface and then dispatching it with the
blunt weapon of your choice - some notables
being sledgehammer and brick.
By the very definition of euthanasia this
method is not completely humane - the fish
has to be handled which causes stress, it has
to be taken out of the water, which causes
stress, and it has to be laid on the ground
(or whatever surface) which also causes
stress - this is all exacerbated by the
amount of time it takes for you to line up
your 'shot'.
An alternative to laying the fish down to hit
it with an object is to hold the fish by the
tail and swing it against a hard surface head
first - this may not be successful on the
first attempt however and as such is not
recommended.
Although the actual death is quick (so long
as you get it right first time) the process
can be convoluted which comes under the
heading of cruel and unusual.
Recommended for: Large fish that cannot be
accommodated in any other way.
Not recommended for: Small fish, or those
likely to "flap about a bit"
Humane rating: 60%
Decapitation
Similar to sudden blunt trauma, but the fish
is dispatched by removing the fish's head
just behind the gills using a sharp knife, or
other bladed instrument.
The detractions to this method are the same
as sudden blunt trauma - handling, removal
from water and laying on flat surface all
increase stress before the eventual death. In
small fish you can use a sharp pair of
scissors once removed form the water.
Recommended for: any fish, as long as you can
successfully decapitate in one movement.
Not recommended for: fish that are still
strong enough to flap about.
Humane rating: 50% (this is due to evidence
that brain activity continues after 'clean'
decapitation for up to 10 seconds)
The blender
This method involves placing the terminally
ill fish into a blender and "whizzing" it.
The main problem with this method is that the
blender should be running before the fish is
introduced (head first) to ensure that the
fish doesn't fall below the blades or become
impaled.
Again, you have to catch the fish, handle it
and then dispatch it. Stress levels would
become quite high.
Recommended for: Any fish whose head is not
deeper than the distance from the top of the
blender blades to the bottom of the blender
jug.
Not recommended for: Any fish that does not
fit in the blender - fully grown iridescent
sharks, freshwater rays, you get the idea.
Humane rating: 90% if the blender is already
running, 30% if you have to turn it on after
putting the fish in.
Freezing method:
The idea behind this is that the fish goes
into a dormancy mode as the temperature
decreases. The fish falls asleep and never
wakes up.
The method is you place the fish in a
coverall container of tank water at the
normal temperature - this is then covered to
simulate dark and placed in the freezer.
I am divided on this method and I think that
the humane factor depends on the species of
fish - I know for a fact that when Carassius
auratus and other members of the carp family
are exposed to temperatures lower than 55F
they do indeed enter a sort of dormancy,
their metabolism slows and indicate sleep
behaviour. This does not indicate that all
species enter this state - lower temperatures
spontaneously create diseases like ich in
some species.
Also the temperature drop in a freezer is
quite rapid (the temperature will drop
roughly 1 degree for every five minutes in
the freezer) unless you were to place several
gallons of water to freeze. We have acted in
the time that we have cared for the fish to
protect it from rapid temperature
fluctuations and yet are now doing the very
thing that we have tried to avoid.
Temperature changes such as described above
will produce stress until death, or the
dormancy stage is accomplished (if the fish
is stressed there is no guarantee that it
will enter the dormancy stage - a human that
falls asleep on a freezing hillside will wake
up before freezing death and only loses
consciousness as the body's homeostatic
system constricts bloodflow to the
extremities (including the brain) to keep the
core warm, there is no reason why the same
shouldn't happen in fish).
Recommended for: tenuously recommended for
cold water members of the carp family and any
other species that has a proven dormancy
stage.
Not recommended for: tropical fish
Humane rating: 85% (for carp family) 25% (for
tropicals)
Temperature shock method (freezing)
This method utilizes the coldest water you
can find - a bowl of water that has been
placed in the freezer long enough for the
surface to freeze is good. The surface ice is
broken and the bowl taken to the dying
fish.
The fish is then captured and dropped into
the freezing water. The difference between
the temperature of the tank and the freezing
water causes an instant fatal shock to the
fish nervous system stopping all organ
functions instantaneously - anyone who has
found themselves suddenly in water that is
much colder than your body temperature will
know the feeling when you initially can't
breathe (people have died of heart failure
under similar circumstances), it is like that
but much more severe and sudden.
A variation on this is freezing alcohol (pure
or vodka)
Stress is caused in the handling of the fish,
but in most of the methods the fish must be
handled - however this handling is brief.
Recommended for: tropical fish.
Not recommended for: coldwater fish.
Humane rating: 100%
Temperature shock method (boiling)
Works in the same way as the above
temperature shock method, but involves
dropping the fish into boiling water.
The main problem with this is not the effect
on the fish, but rather our perception of it.
Boiling something is usually for food, and
things that are boiled are usually dead
(lobster being the exception and falls under
this category).
However this method is completely acceptable
and humane for coldwater fish.
Recommended for: coldwater fish.
Not recommended for: tropical fish.
Humane rating: 100%
N.B. Caution should always be exercised when
working with hot liquids, surfaces and
devices.
Alcohol
As pure as possible - vodka, tequila.
The method is that you have the alcohol at
the same temperature as the water in your
aquarium - the fish is introduced to the
alcohol and immediately becomes overwhelmed
by it.
Alcohol works like an anesthetic and is at
lethal levels. The fish will instantly be
paralysed and unconscious, death follows
quickly due to respiratory failure.
An alternative is freezing alcohol as
mentioned above - that might, just be
overkill.
Recommended for: all fish.
Not recommended for: fish who attend
alcoholics anonymous.
Humane rating: 100%
MS-222 (or other veterinarian anesthetics)
This is possibly the Rolls Royce of fish
euthanasia.
Like all anesthetics, if you administer too
much death occurs. This is particularly
useful if the fish is solitary in a
quarantine tank. You can make a bath of it,
which is the most economical way, but for
minimal stress you should use it straight
into the tank.
MS-222 is a white powder and should be mixed
with water prior to use. The MS-222 solution
is then poured into the tank water. Death
occurs in the same way as alcohol above.
Recommended for: all fish.
Not recommended for: N/A.
Humane rating: 100%
N.B. MS-222 and other veterinarian
anesthetics should be handles with care and
stored securely.
Electrocution:
This method is dangerous - it should not be
attempted by unqualified individuals!
This method involves placing negative and
positive electrodes in the aquarium water and
producing a charge sufficient to kill the
fish.
The key to this method is amperage. It is the
amperes of a current that kill, not the
voltage. Volts is another word for the kick,
while amperage is the power in real terms.
Death occurs due to cardiac arrest when
accomplished properly.
Recommended for: all fish.
Not recommended for: anyone who doesn't know
what they are doing.
Humane rating: 100% (when done properly)