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The Goldfish Gazette, Issue #040 -- Line Breeding
April 29, 2017

Goldfish Care Tips and Guidelines

A Free Monthly Resource For Goldfish Enthusiasts
April 2017
Issue #040

In This Issue
Does line breeding weaken the strain?

Aside from commercial Goldfish production, breeding should always be used to improve the quality of a Goldfish strain.

Line Breeding

Goldfish breeders who want to improve the quality of their stock must line breed their fish. But what affect does line breeding (inbreeding) have on Goldfish over time?

What Is Line Breeding?

Line breeding means breeding successive generations of fish back to the parents, not breeding successive generations of fish to each other, even though they may be better quality than the parents.

The reason for this is the parent fish passed on genes from their parents that hopefully produced some good quality offspring (generation F1).

F1 fish will be carrying some of the genes of the parents, but also a large number of the grandparents’ genes because of the second generation throwback factor.

The fry of a F1 fish to F1 fish spawning, (generation F2), would show a large number of traits of the parent fish, the fish you are trying to improve on. By breeding F1 fish with the parent fish, you have a much better chance of getting higher quality fry.

Genetic Diversity

The only problem with line breeding is it weakens the strain because you are using a small pool of genetic diversity. It’s called inbreeding depression.

Some guppy breeders have been line breeding the same strain for more than 20 years with no problems, but each variety of Goldfish has been line bred for hundreds of years so tend to become less vigorous and less inclined to breed after a time.

In wild communities of Goldfish living in small enclosed bodies of water they are forced to interbreed, but the purity of their genes means it takes some time before mutant fish start to appear. Natural selection then removes these fish from the wild population.

It has been suggested that ponds full of carp being raised for food is where fish with a golden coloration first appeared. These early mutations were probably due to inbreeding within a small group of confined fish.

Creating More Diversity

There are several options available for ensuring line breeding doesn’t weaken your strain:

1. You can maintain several strains of the same variety and interbreed them when inbreeding depression starts to appear. Some disadvantages of this method are the numbers of fish required to be kept, the amount of room necessary to keep the strains separated, and keeping very methodical records over a long period of time.

2. Cross breeding with one of the least developed varieties such as a Common Goldfish to re-establish strong un-mutated genes.

Despite my advice about never cross-breeding Goldfish varieties, this is exactly what one notable Veiltail breeder does. It then takes him 7 years to get the quality of his Veiltails back to a high standard. The biggest disadvantage of this method is the amount of time required to re-establish the strain to anything like the quality it started out at.

3. Obtain fish from a completely different strain of the same variety. This is the method I am using for my Black Moor strain. I bought a hundred fry from another breeder in a different part of the country. After going through the selection process I am left with three fish I am happy with.

Their body depth is superior to my fish but mine have better eye and fin development. The disadvantage of this method is not knowing what defects you will introduce into your strain. I had to discard a few very nice fish because they had developed bent pectoral fins, something I will watch for when I breed them to mine.

I now realize the difficulty I had breeding my Water Bubble Eyes last season was probably caused by inbreeding depression, and not one of the many reasons I started imagining. I am now on the hunt for a strain of Bubble Eyes from another part of the country to cross with mine.

To read more about starting your own Goldfish dynasty, click here...

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Next Month's Topic

Commercial Goldfish Culture

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