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Inbreeding to Improve Betta Fish Strains

Inbreeding to Improve Betta Fish Strains


If we got $1 usd for every time someone said line breeding was something that should not be done, I would be rich.


I often get questions regarding the inbreeding relationship of the betta fish we sell. The uninformed A typical betta aquarist wants to always be sure that each betta strain will consists of a group of fish that are unrelated, because they have been told over and over that inbreeding causes so many problems. Certainly, you are now thinking that none of us want fish that will easily degrade with each generation, right? So, everyone thinks the answer must be to “always breed to an unrelated fish”, or “if you must breed to a sibling, then certainly for no more than a generation (F1) or two (F2).” I am totally not sure how these types of perceptions come about, but they are very common in groups and passed on to new breeders over and over like a candy bar at a fat loss clinic. In fact, I even see so called experienced betta aquarists frequently warning against inbreeding because it does this or does that to fry and recommending frequent out-crosses to keep lines vigorous and fast growing. Are you ready for the shocking truth, you might need to sit down for this one? This is 100% untrue, false, BS and just a wife’s tail from breeders or so call experts who know next to nothing on genetics! Inbreeding does not automatically make for worse case fish, or stunted fish or bad swimming fry or low egg count or even how the fish acts (bettas have a 10 week or so memory anyway). The inbred fish will not automatically inherit anything that makes them less vigorous or slower growing, smaller or anything else for that matter. Color is not always going to degrade in your betta and neither is the ability to breed prolifically. So, all the talk from the so-called experts is just barfed up junk with no science behind it at all. Move on to a new breeder before you get substandard genetics.


So, what is really happing when you inbreed those beautiful bettas? Is there some gene that is mysteriously created out of thin air that destroys the line? Let’s talk science now and we know for a fact that some inbred lines of betta fish exhibit many problems, some more than others. Why is it? Well, are you sitting in your chair? The answer is really quite easy. When inbreeding, we double-up many genes like Si and Nr1 and Nr2 and blond ect ect. In other words, they end up in homozygous pairs in the betta at the same location on the chromosome. If the gene is recessive, then the trait in the betta is hidden from our view if the fish is heterozygous for that gene. The trait expresses once the recessive gene is homozygous on that location. If it’s a trait you like, well then that’s great. If it’s an undesirable trait, then that’s so bad, right? Well, not necessarily my friend. If you want to eliminate undesirable recessive traits from your betta line, then one way to eliminate them is to make them appear, so you know what is there and can select new genetics against them. Starting to see the real picture here of good breeders!


If the undesirable gene in your betta is a dominant gene, then eliminating it is very easy because you know it is there, right? Every betta containing one, will express the trait and you will see it and you can select against it. So, when inbreeding your bettas, the only way for a line to express that nasty undesirable trait, is for the person who supposedly knows so much to fail to test for it and then select against the trait. Yup, that’s right you can now see inbreeding can result in problems when in the hands of an inexperienced person, the main reason is because they fail to select against the undesirable traits in their bettas. In the hands of the knowledgeable breeder with years of breeding under the hood, it is a tool we use that brings out undesirable traits so they can be selected against and changed or removed at will. Now, keep in mind this is not exactly an easy process for new breeders as they might not know colors or genetics yet. To do it correctly will require raising the betta until the trait would normally be expressed like in nemo or koi, and sometimes you have to test-cross you line to determine if the gene is present in your breeding pairs. However, with saying all this, rest assured that in the hands of the knowledgeable betta breeder, inbreeding or we call it line breeding is one hell of a useful tool that all breeders should learn. So, in theory, you could select against these undesirable genes at any time, until you have a line of fish that only contain the genes you want and see and are virtual clones. But in practice, this wouldn’t happen, as every single thing would need to be duplicated right down to the cell but the object is to come as close as you can to creating a clone with only the traits you want in your betta line.


The biggest reason I can think of to inbreed would be because it can be very beneficial when trying to “fix” a trait you do not like… If the trait in your betta is a desirable one that is determined by a recessive gene or maybe even multiple recessives, then the quickest and sometimes really the only way to acquire its expression, is to inbreed. To out-cross to new and unrelated lines, would make it less likely that they contain the same recessive positive genes even if you get lucky and see it one time. There are many instances I can think of where an out-cross is almost guaranteed to eliminate the expression of a desirable trait for a generation or two, and possible even longer and make you fish go from A grade to D grade in only a few generations and at some point, reach an unfixable point in your life time. Consequently, inbreeding is a useful tool to “fix” recessive traits that you want in your line like DT or CT or bars not patches on nemo.


Inbreeding is a tool every breeder needs to know that can improve a line when used properly. 

I am sure you will not find betta mills using it or the plop and pry breeders using it or even the guy who thinks 2 royal blues make royal blues. But, if you select bettas with only the desirable genes, then unwanted traits cannot appear as the result of the inbreeding, it is just not possible. Now there is one negative that is sure to happen, given enough time and murphy’s law with any line of inbred fish. The genetics of the immune system does not work the same as the other genes in the fish, we wish it did but it does not. A large combination of antibodies is produced as the result of the shuffling of immune system genes in bettas. The immune system genetics a betta gets depends on a diverse number of genes to be shuffled like a deck of cards. In this way, a great number of antibodies can be produced, enabling a defense against a larger number of pathogens and other nasty invaders from the betta’s habitat. Inbreeding leads to the tendency to lose some of these genes over time it takes a very long time not years but decades. This reduces the diversity of the immune system and good immune systems depend on diversity of genes. To counteract these losses, most of us older breeders with some breeding time under us will set up separate lines of the same stock, and then make periodic crosses among the lines to maintain the immune system diversity of the hard work and time in our lines of bettas. If one line loses a gene, another will give it back and it is pretty much a rock-solid good idea.


I just cannot stress enough the use of careful selection of the next generation combined with the modified inbreeding we call line-breeding to be a standard to breed by. It has resulted in some very nice lines of bettas that have been inbred for dozens of generations with no apparent degradation and each breeding gets better and better genetics. In fact, many of these lines are only continually improved along the way by line breeding.


The main reason inbreeding can be so effective with bettas and probably not so effective with many other animals is because of the sheer numbers of fry that most bettas produce in a short time. As betta breeders, we get to choose from many hundreds of thousands of offspring, which enables us to find the individuals (even if few in number), that contain the traits we desire and to “fix” them. This is why it can require a lot of tank space and some very careful consideration combined with good judgment, but it is done all the time. You can not do it with a few tanks and do much line breeding. You would need to relay on a good breeder to give you stocks with the traits already built in from there line breeding. This is the one reason not to buy a fish from a breeder who can not show you several generations of the same color and type.


We still need to kill the BS on out-crossing and how it can also be used as a breeder’s tool to improve their stock. But that will be a later post, I think. There is a lot of info to soak in and a lot to relearn here for some. My professional advice is to get your line breeding down first and then work on out-crossing. The reason that you will want to do it this way is that line breeding is far more important the out crossing if you want beautiful looking bettas all the time. You will see over time in the future as marble starts to get into all bettas that line breeding will save your solid colors and dragons for sure. For the breeder reading this I will leave you with laugh and a smile “never buy a fish from a breeder who say why would you need a cellophane”.





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