in breeding in fish? - The Planted Tank Forum

 
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post #1 of 3 (permalink) Old 07-06-2013, 11:34 AM Thread Starter
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in breeding in fish?

iv'e finally located someone with dwarf mosquito fish very rare indeed in my area (infact no one seems to know what they are locally and even on the internet they seem to be rather rare), problem is the person has been inbreeding them for a while and has a few mishaped fish (no choice as he can't seem to find any one else with them to swap fish with and get some new blood). Iv'e asked a few local fish keepers and the general conception seems to be that inbreeding is fine infact rather encouraged in my area. The general reasoning iv'e been given for this is that it is used quite alot to get new/keep new mutations pure and that it doesn't effect fish like it does other animals. Im not so sure on this and the topic seems to be a rather heated debate on the internet, some saying that in fish you can cull any weak/mishaped fish unlike a dog or human, which therefore makes it ok to inbreed other says completely different. Sorry for the long rather jumbled post, any one have opinions on inbreeding is it ok to do with fish or not?
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post #2 of 3 (permalink) Old 07-06-2013, 06:24 PM
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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?
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post #3 of 3 (permalink) Old 07-07-2013, 09:31 AM Thread Starter
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Quote:
Originally Posted by Diana View Post
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?
thanks for the reply, so what about things like the immune system iv'e heard that if you continue to inbreed without introducing new blood, then it weakens the immune system (something to do with antigens getting lost over the generations). is this true or does it just work the same - cull any fish that seem to get infections easier/faster than the others?
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