Fish Linebreeding Techniques

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If you've read my previous articles on inbreeding and outcrossing, you have the knowledge on how each can affect the look of your lines. Now, I'll tie the two methods together with the technique needed to accomplish your goals.

Once you have obtained all the fish containing the traits you desire to breed into your line, you need to have a system to keep the fish strong and good looking long term. If you want to maintain the desirable traits and keep the immune system strong, you have to combine the techniques of inbreeding and outcrossing. This is accomplished by setting up different "lines". A minimum of two lines are needed, but if you use only two, it will make your work that much more difficult and increase the likelihood that you'll have to make unrelated outcrosses more frequently than you'd like. I consider 3 distinct lines the minimum needed for long term linebreeding.

The concept is simple. Maintain each line separately, as if they were different strains. Improve each line using the best techniques for strict inbreeding. Each should become the best you can make it. Periodically, each line is then outcrossed to one of the other related, but separate lines. This type of outcross will maintain a strong immune system, yet since you're outcrossing to a related line, degradation of homozygous desirable traits will be less. I recommend inbreeding at least 3 to 4 generations before you outcross to one of the other lines. Do it more frequently, only if you see a problem you can't eliminate through proper selection.

The outcross rotation method of the lines isn't too important. Just do it in a systematic way, so each line gets crossed into each of the other lines before you end up starting the cycle over. Assign a letter to each line, ie. A,B,C, and then on each outcross, add the letter of the outcross in lowercase, ie. Ab, Bc, Ca, or Abc, Bca, Cab.

Using this method, you can go for decades with just a couple complete cycles of the lines. Just keep in mind when linebreeding, one of the only reasons to make an unrelated outcross is to bring in desirable genes your lines do not contain.

Enjoy your fish,

Steve Rybicki

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