Pond Goldfish Colour and Breeding
Long story short, we've had a pond and goldfish in our garden for the last fifteen years. We've moved twice in that time and either took some or all of the goldfish with us. The first year at our last house, with a big pond, we had more than 30 fry survive to adulthood. We never actively tried to breed the fish, we just let them do their thing.
Anyway, the house we're in now has a much smaller pond than the last and we brought about 6 goldfish from the big pond with us (including the three originals that weren't snatched by kookaburras). We had another attack by a kookaburra and lost another two fish shortly after the move.
Two days ago, five years after the last move, we found a collection of 'new' fish. About four adults (approximately 2 inches long) and at least another four fry (about one inch long). I've gone into this rather long backstory because I'm a little bit worried about inbreeding. I can't say for sure if they are inbred but it concerns me.
Is there anything I should look out for or is it nothing to really worry about? I don't want to accidentally breed sickly fish, it's not fair on them.
Also, all of the new generations are metallic brown, although their parents are all colourful (they're gold comet x shubunkin). In the past few of our bred fish stayed brown into adulthood, I think five at most, so I'm curious as to why all of these fish are still brown. Is there any chance that these fish may still change colour or will they just stay brown?
Inbreeding is something to be kept in the back of one's mind, but professional breeders line breed, (breed children back to the parents), as this ensures that desirable traits quickly become established.
I also line breed and I haven't seen any evidence of genetic issues yet. Having said that, I do occasionally buy in new fish to deepen my gene pool.
If you are concerned, as you have been breeding the same small group for many years, purchase a few fish to introduce a new blood line.
Regarding the colour issue, you mention that the fry were from a gold Comet x Shubunkin cross.
This is the problem, as Comets are bred for intensity of colour, and a quick colour change from brown to gold.
Shubunkins don't go through a colour change as they are a different scale type (nacreous).
I have found when breeding Shubunkins the small number of metallic fry produced (25%), either don't change colour, or are very slow to change.
Have a read of this page
which explains cross breeding different scale types.
Another point to consider, if a small Goldfish is bright orange, and another is drab brown, which is most likely to get eaten by predators?