Deformities in Tank Raised Fish
by Sean Furney, of Oklahoma City
Reprinted with permission, from Sean's website, www.theaquariumexchange.com
Aquarticles
While there is still some argument about the causes of deformities in tank raised fish,
there is no doubt that they are a plague to the aquarium hobby. Some things we can do as
conscientious fish keepers are to avoid buying fish from stores or wholesalers that
consistently sell deformed specimens, and carefully cull any even slightly deformed
specimens out of the fish that we produce.
First let me cover the common causes of deformed fish.
- The first and probably most common is genetic defects. These defects are caused by poor
selection of breeding stock. Fish are more prone to genetic defects the farther out of the
wild they are bred. You are also more prone to cause genetic defects if you, or the person
you received the fish from, either don't select top quality specimens or breed too closely
to the same genetic pool.
- The second most common reason for deformity is cross breeding (interbreeding of two
different species) of fish. This does not happen too often, however you will occasionally
run into it. There are some tell-tale signs of this that I will cover later.
- There are other reasons why deformed fish are produced, including overfeeding of fish to
cause increased growth rate. It can also occur if a food that is too rich in proteins and
fat is used.
- The opposite can also occur - underfeeding of fish can result in fish whose growth is
stunted. This is often harder to detect at first, as most of the time you do not know the
age of the fish when you purchase it, and even if you did it would be awfully hard to
memorize the approximate growth rates of so many species.
The first step in taking preventative measures is to identify deformities. You must
have good knowledge of what the fish you intend to keep looks like. One good source for
this type of information is books, which often have good accurate representations of what
particular species are supposed to look like. Another good source of information is the
Internet. However I would personally recommend looking at several web sites and getting a
compilation of information from them. Unlike books which usually have a technical editor
or which are written by someone who has a vast amount of knowledge on the subject they
have written about, anyone can put up a website. While most of these web sites have good
intentions they may have limited knowledge of what species they have, and many are limited
to nomenclature of species or common names that they purchased their fish under. If you do
not have access to any of this information or cannot find information on the fish that you
wish to purchase, there are a couple of other guidelines that you can use.
These guidelines include studying the others of the same species that are in the tank.
You need to look for consistent body shape. All fish of the same species should have the
same body shape. You can also study differences in barring patterns and coloration. This
is a little more difficult in most fish because you must take into consideration
sub-dominant coloration and barring patterns, female coloration and barring patterns, as
well as fright patterns for the particular fish species. As you can see this is a little
more difficult proposal. These methods are often employed in verifying correct
identification in species where the females of several species or even just regional
variants are very similar, particularly in wild caught fishes. It is best when acquiring
wild caught fish to sell, that you raise the first batch of fry to a size where the
males are fully colored. Then you will be able to tell if your fish have cross-bred. If
the males of the fry are identically colored to the father they are a true species more
than likely.
Now we can cover the proper techniques for breeding stock selection. The best way to
establish a breeding colony is to buy many juveniles, preferably from different sources.
You should always make sure you get your breeding stock from people or businesses that
have the best quality fish, even if you have to pay a little more. It would be better to
get all of your stock from one source than to get stock that is not high quality. It is
best to grow your stock up to at least young adult size. If you have purchased your stock
from multiple sources it is important to keep the specimens separated in order to be sure
of the genetic diversity that you want. Once they have reached the proper size, select
females from one set of fish and a male or a couple of males from the other set of fish.
When selecting your breeding group, you have a couple of options depending on what you
want to breed for. Most commonly in most species of fish you would want to select
specimens that are as close to their wild caught relatives as possible. This should
include size, coloration, body shape and barring patterns. Barring patterns in most
species should be straight with no irregular shapes and should match exactly from one side
of the fish to the other.
As far as being able to tell if a fish has been overfed or stunted, these problems are
even more difficult to detect. Overfed fish will often exhibit characteristics of genetic
deformities. The most common characteristic that I have seen in juveniles from overfeeding
is a fish that looks stumpy (growing taller and more broad than it should be for a given
length.) These fish usually have a significant amount of fatty deposits. These fatty
deposits can cause health problems in fish. They can also cause problems with breeding.
Stunting in fish is the hardest characteristic to recognize. The easiest to
determine is in fish that have different adult coloration than juvenile coloration. If you
see a fish that is exhibiting adult coloration at a smaller size than is usual for the
species this is often an indication of growth problems. Of course this means that you must
know about what size the fish colors up.
There is one more thing to cover that doesn't really have to do with deformities but it
does related to being able to buy fish for breeding purposes. This is fish marketing.
Unfortunately in this day and age of wanting to make more money off of their fish related
business, some breeders and wholesalers have resorted to either changing fish names or
adding fancy superlatives to the names of their fish. As far as changing fish names I have
seen everything from reverting to older scientific names that are no longer in use to just
changing the names of the fish entirely. I have seen wholesalers use names like super red
top for wild caught fish, even though they are collected from the same location as every
fish of that species that everybody else is selling. This is an obvious attempt to make
their product seem superior by using fancy names. As far as an example of changing names
entirely, there are a group of African cichlids known as peacocks that has a red strain
that has been developed in the aquarium hobby. Some breeders/wholesalers use several
different names for the same fish. These names range from Ruby Red to German Red to
Rubensens to Ruben Red. Recently they have even added another name of Chidunga Rock, which
is just the collection point of the fish that originated the red strain. This attempt at
deception in the aquarium hobby only makes it hard to keep track of which fish are which.
Just keep in mind that the person who is selling the fish might not be the best person
to ask about the quality of their fish. I have heard a wide variety of excuses for
deformities in aquarium fish, such as "There was too much water current in the
grow out tank and that is what caused their face to be rounded", or "The females
applied too much pressure to the fry while they were in her mouth", to
account for a wide variety of body shape problems in mouth brooding fish.. I have even
heard an excuse of sand irritating the gills to explain why you could see red in the gills
of fish, when really part of the plate that covers the gills of that fish were missing.
So as you can see selecting good quality breeding stock can be quite difficult and
knowledge is required on the part of the breeder to select good quality stock.
So if you want to get into breeding fish it is important to get out and seek
information on any species that you wish to breed. If at all possible try to see as many
examples of the species you want to breed as possible. This will give you a better idea of
the quality of the fish that are available to you. It is you as a fish keeper who is going
to determine the future of this great hobby, by buying your fish from businesses or
hobbyists that only deal in top quality fish and by carefully selecting any breeding
stock.
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