Question about inbreeding

[valkyrie]

Hi All,

New to this forum so apologies if this is a silly question.

To set the picture I have a 900gal pond give or take a couple of gallons, heavily planted. it is about 4 years old and going well. When I originally stocked the pond with shubunkins, I put 20 in the pond from 4 different sources. Well, as you can guess their are quite a few more in the pond at present. (no I have not tried to count them)

My question is how many generations before I start to get worried about inbreeding? I have already taken some of the offspring with undesirable traits (there was nothing wrong with them just not what I am looking for in a shubunkin) from the pond and given them to my LFS. Should I be seeking new blood for my pond already? If not when?

Any suggestions appreciated, I didn't intend on breeding them to start, but nature has taken its course and I now have some very nice fish and the bug has taken hold.

Cheers
Debbie

[HNLim]

Its a devil and the deep blue sea decision.

[bekko]

In-breeding is not going to be your problem. Your problem is that if the population is not being culled with only the better ones kept, then the gene pool will deteriorate and eventually revert back to wild carp. Obviously, there is a limit to the number of fish you can have in the pond, so your goal is to get rid of the poor specimens to make room for the better ones.

-steve

[valkyrie]

Hi Steve,

Thanks for the info. So just to clarify. If I continue to take out the offspring with undesirable traits then inbreeding should not become a problem. Is this correct?

Thanks
Debbie

[Virginia ranchu]

As Steve said, the main concern would be overcrowding. I'm assuming that the older fish remain in the pond as well, so they are still breeding. The older fish are not as inbred as successively inbred fish (brother to sister for several generations). In a pond situation, there will be competition, and the less fit fish will likely not survive anyway. This is basically no different than any other pond fish population. I know of bluegill populations in farm ponds that are going on 40 years will no negative effects.

It is a different story when fish are aquarium bred and only one or two pairs are selected for breeding each year (brother and sister or backcrosses). After several generations, the gene pool will get pretty "shallow".

Rob

[Virginia ranchu]

Oh yeah, it is worth mentioning that if you allow the shubunkins to breed randomly without selecting for the most desirable coloration, they will likely begin to revert to a wild type color, or at least a less appealing color.

[johnatoranchu]

Steve's response is spot on. It is unlikely that inbreeding will be a major problem but degredation of the "type" through lack of culling could be. The problem of course is what to cull and if you are not interested in showing and therefore bound by show standards culling could be difficult. Presumably you already remove all the metallic and matt (white) babies as soon as you can plus any that have obvious deformities. Then it is simply a question of deciding what you like and if for example you like pale blue fish with red heads because they are easily seen in the pond then cull all those which don't have those qualities. To avoid potential inbreeding problems in the future always ensure that you have at least 20 fish in the pond and (using my example above) if you only have 10 fish with red heads and blue bodies then make the number up to 20 by including the best red headed fish which don't have pale blue bodies and/or the best pale blue bodied fish which don't have red heads. Undertake a complete cull of all fish in the pond once a year, perhaps when that year's young are about 3 inches long, removing all those fish which don't meet your personal ideal. In due time you could have a very nice pond stocked solely with red headed blue fish - or at least that's the theory!!!
John

[bekko]

... and after that, cull for tails. Assuming you have the usual Japanese/American shubunkin, you would want to select for long tails which are held well-spread. Otherwise, the tail length will become shorter with successive generations. Males with less flamboyant tails are more agile and have an advantage at spawning time.

-steve