Good questions. Most of which I do not have answers for.
Some background. My main pond is 3 acres and was 2-3 years old before any CNBG were introduced. So the pond was likely at carrying capacity and had northern BG in the tens if not hundreds of thousands.
I stocked 100 CNBG and 175 RES in my 1/10th acre forage pond. They spawned and the pond likely went to carrying capacity with a large percentage being CNBG. I fished out what I could what had grown to be 5-7" original CNBG and put them in the main pond. I also trapped lots of fingerlings and put in the main pond. At year two of the sediment pond I had a fish kill and dip netted thousands of CNBG out before they surely would have died and put them in the main pond. So I put maybe a few thousand CNBG into a pond that likely had tens of thousands or more of northern BG.
The point of all of this is that my main pond being 30 times larger, even if both ponds were at carrying capacity and all the CNBG from the forage pond went into the main pond there would still be at least 30 times more northern BG compared to CNBG. I suspect it is closer to 100 to one. Point being I rarely, but do occasionally, catch a CNBG. The females I sometimes have a hard time telling. I will catch a fish with the wide vertical stripes common to CNBG and I think it may be a CNBG but my fish ID skills are not good enough to tell for sure. Once in a great while I will catch a nice male with traditional markings that it is certain to be a CNBG. So the CNBG are a very minor part of my total fish population in my main pond.
Will they intermix? My understanding is that they will and one reason I got some was for genetic diversity. Are they "hybrids" with hybrid vigor? My understanding is they are not. Since they are actually the same species (each a sub-specie) they do not take on the trait of a hybrid but will take on mixed characteristics. If the experts say otherwise, believe them over me. That is just how I understand it.
I am not far enough along to know if I have any mixed northern BG/CNBG. It is possible at this point because I had transferred the 6" nominal adults last year as I caught them. They have had time to spawn. But since I am having trouble identifying female CNBG for sure I'm not sure I will be able to tell a mixed one when I see it. That could very well be what I am seeing with the wide vertical bars on some of my fish. The CNBG could already be intermixing.
I'm not a purist so it does not matter to me. I like the hybrids and I like both types BG. As long as they are healthy pan fish that is my goal for the main pond - a pan fish pond. I have been harvesting some really nice 9"+ HBG that were originally created in my sediment pond and transferred to the main pond. (a few GSF got in that sediment pond and created a LOT of CNBGxGSF hybrids and a much lower amount of RESxGSF hybrids - these also got transferred to the main pond at fish kill time and some before on purpose).
That is what I think I know to date. Next year I will try to notice and take pictures if I see what I think are CNBG northern BG crosses.
References:
fish kill post in sediment pond thread Main pond thread Sediment pond thread Edit to add a another picture of one I caught today.
