Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
If you are inbreeding without culling you can go to about the 5th generation before problems set in.
If you regularly cull then you can go on a lot longer.
This is how different color morphs or long fins are discovered, bred and increased.
If you can isolate the breeders and keep records you can clean up the gene pool, but it will take time.
Keep each fish separate. Breed them and watch the babies. This is complicated in live bearers since the female stored sperm and may have several litters from one mating, and any one litter may have several fathers.
But make notes like this:
Male A x Female A = whole litter deformed.
Male A x Female B = Babies look normal, but are weak, die in just a few days.
Male A x Female C = 20% deformed.
At this point I would be wondering if Male A is really a good one to keep in the gene pool. Take the normal fry from Male A x Female C and keep track of their babies. If they also produce a high level of deformed babies I would remove Male A from the gene pool. Monitor his other normal sons and daughters for deformed babies. You may have to cull very heavily to get rid of his genes.
The next block of records can be compared to the ones above.
Male B x Female A = Odd colors, but healthy, none deformed. (Possibly a good source of color morphs- try isolating and inbreeding the babies with colors you like)
Male B x Female B = Babies weak, 50% loss in the first week.
Male B x Female C = healthy fry.
Looks like the 'weak fry that die soon after birth' might be a problem carried by Female B. The question is: Is she getting old, and her system is just not up to nourishing the babies? Or is there a real genetic problem? If there are any strong survivors breed them and see.
Some genetic problems are pretty subtle. How would you deal with this?
Fish produce deformed fry when they are poorly nourished.
If they are fed the wrong food, this is obviously a fixable problem.
But if they are incapable of properly digesting the food, and continue to produce bad fry, even when fed the right food, is this because they were poorly nourished when they were growing? Or does the fish have an actual genetic problem (such as lack of an enzyme or something) that it can pass on to the fry so they also cannot assimilate the nutrients in the food?