This probably isn't anything new to you seasoned pondmeisters, but I thought it was interesting and wanted to share.
I stocked my mostly predator-free pond with FMH about 1 year ago. I wanted all black FHM, but was given a mix of about 80% black, 20% rosy red. It's been really interesting to see the results of the reds and blacks interbreeding.
I've seen several minnows of larger than fry size that actually have splotches of both red and black over their bodies. Most minnows of this size class are either solid black or solid red. From my random observations I'm guessing that the ratio on the larger fish is around 80% black, 15% red, 5% mixed.
I'm currently seeing a lot of tiny fry and they're around 25% red, 75% black. I haven't seen any mixed-color fry, only solid red or black. I'm not sure whether any of these fry will exhibit the mixed splotches when they get bigger, or if they'll all stay solid colored.
All of the FHM seem to school together with other FHM of similar size. Each school is around the same ratio of colors, so they don't seem to segregate at all by color, only by size.
I'm not sure of the genetics behind this... I'm also guessing that natural selection will eventually affect things since the reds are much easier for birds and other fish to see. Of course I'm only seeing a small sample of the total fish in the pond. Just whatever swims close enough to shore for me to see or wanders into one of my traps.
It's really interesting to watch. Sometime I'd love to put some red and black minnows together in different ratios in tanks in a controlled environment and see the results.
