A guide to selective breeding and wild-caught fish
While you may have already enjoyed some success breeding some species of fish, there is an additional level of skill necessary to ensure that the specimens you breed are of the highest quality. In order to maximise the health of your fish, you must be aware of how to use reproductive biology to your advantage.
Once you understand the basics of breeding, you can begin selectively breeding fish with certain characteristics. Doing this successfully, however, requires some understanding of the genetic makeup of your fish, and the manner in which they will pass on desirable characteristics.
These characteristics can take any number of forms, from specific variations in colouration such as seen in many species of betta splendens or fin variations such as those commonly bred out of goldfish. Different colours, sizes, body shapes and even behavioural attributes can be bred in subsequent generations of your fish, but doing so requires paying attention to your fish pedigree.
Fish domestication designations or generations removed from the wild
Most novice aquarists are not aware of the fact that domesication designations for fish exist. These helpful little tags are often added onto the end of the description used to identify the fish:
- WC, wild, or F0 – The most evident of the tags, this indicates a fish that was caught from the wild
- F1 – First generation. This is a fish whose parents were both wild-caught fish
- F2 – Second generation. This indicates that both parents of the fish in question were F1 fish
- F3 – third generation and onwards are considered domesticated or tank bred fish
There are some important differences to consider between these options. First, wild fish are generally the most expensive specimens due to the increased costs of catching, importing and transporting them to your tank. However, they generally enjoy the most successful genetic makeup and, if gifted with a special characteristic that you want to breed, often represent the best chance of passing it on to their offspring. These fish are the most vibrant, naturally colourful and hardy specimens found in an aquarium. But they may be harder to keep in an aquarium because they are adapted to a life in the wild.
F1 and F2 fish are also valuable from a genetic point of view, although slightly less so, since the reduced genetic diversity of an aquarium tank will cause the genetic line to gradually degrade over later generations. Most breeders do not bother identifying fish that are past F2, and it is rare to see any fish advertised as such. As opposed to wild caught fish these specimens show a degree of domestication and will be easier to care for in an aquarium.
The longer a bloodline of fish spends in captivity, the more likely it is to fall victim to genetic defects or just a lack of genetic vitality. This is caused by inbreeding of related fish. Some of this may be relatively harmless, but many will lead to greater complications over time. For this reason, it is important to maintain genetic diversity when breeding in order to keep your fish and their offspring healthy. This can be achieved by keeping careful note of the ancestry of your fish to avoid closely related specimens breeding with each other.
Selective breeding of fish and genetic diversity
The most subtle skill in selective fish breeding is maintaining the appropriate balance between the genetic traits that you wish to pass on and the undesirable ones that will make your fish weak and susceptible to illness.
The importance of this balance is readily apparent in most fish species: A mass-produced specimen that has been grown on a fish farm with limited genetic diversity will be less vigorous and have duller colouration than a freshly-caught wild fish of the same species. In order to guarantee the best results for your selective breeding attempt, you will need to carefully select your fish and their mates. It is possible to reinvigorate a breeding group of fish with the introduction of 1 or a few wild caught specimens.
In the case of highly developed forms such as guppies that are markedly different in form and colour than wild specimens, the process is a lot more protracted. Breeding a wild caught specimen with a highly developed fish will most certainly invigorate the line with strong and healthy youngsters. But the likelihood of obtaining youngsters that resemble the developed form is almost zero. It will take a lot of breeding back to the original pedigree to regain the original developed form while maintaining some of the new found vigour in the strain.
There are two ways that you can improve the pedigree of fish
• Line breeding—The process of line breeding involves keeping the genetic blood line of your fish within the family in order to bring out the desired characteristic more. It is also often called inbreeding, and is the most successful way to ensure that a desirable physical attribute gets passed on.
• Outbreeding—This is the breeding of a fish with the characteristic you are encouraging to an unrelated fish from an entirely separate bloodline. This can be an important step towards ensuring the health of your fish after several generations of line breeding by ensuring that genetic diversity remains high and your fish are born healthy. One thing that you have to remember is that some feature of pedigree is carried by the male and others by the female. So when outbreeding you will need to outbreed both males and females otherwise important traits may be lost.
Advanced aquarists will often use a technique called parallel line breeding, in which several different bloodlines all featuring the desired characteristics will be bred and raised in parallel. After every 3-4 generations, they will be mixed with one another, offering the benefits of outbreeding with a vastly lower chance of losing their special line bred quality in the process.
A term often used by selective fish breeders is hybrid vigour, which is used to describe the better growth and survival rate of an outbred specimen than those of the inbred parents. Just like any other species, genetic diversity is the key to success, and with the right balance you should be able to raise healthy fish with your desired characteristics.
Choosing between wild-caught fish and later generations
If you would like to enjoy the greatest chance of success with your selective breeding operation, it is highly recommended that you start with wild-caught fish. This is not always possible, such as in the case of Fancy Goldfish, which do not exist in the wild at all, and many other common species as well, but if you can get wild specimens, you ensure the greatest genetic starting point.
Wild fish will often have the best colouration available for a specific species and produce the healthiest offspring. If you are able to get a hold of two wild-caught fish, you can begin breeding and sell your F1 fish for a reasonable price. This is especially true if you have already marked the beginning of a desirable trait through the union, which you can subsequently line breed for greater emphasis if you choose.
If wild-caught fish are unavailable, you can still gain the benefits of genetic diversity through purchasing two F1 fish from separate sources, as well. However, you will have to mark their offspring as F2 fish, which will diminish your rate of return if you are breeding specifically for profit.
In many domestic species of tropical fish that have been tank bred over many generations, wild fish are just not available either because the cost is prohibited, they may be a protected species, or they may have become almost extinct in the wild. In this case, some aquarists try to recreate the original form and colouration of the wild caught ancestor. They do this by selective breeding, but not to produce a fancy form or colour but to try and get back the original wild form. The wild form is usually stronger, has better finnage and better colouration than the mass produced specimens usually available. This is achievable, but it will not result in fish with the same vigour as wild specimens nor will it create fish with a diversified genetic make up.
A final comment about wild-caught fish should be made: Not all vendors get their fish from sustainable sources, and there are even those willing to sell tank-raised fish as wild-caught ones in order to make a quick buck hoping the average aquarist will not know the difference. Buy your fish from an enthusiast or a trusted vendor that runs a long term operation and your breeding program will benefit as a result.