I think you guys are describing what sounds like a perfect example of local adaptation. There are a number of studies that point out large differences in a species behavior/biology based on local adaptations needed to survive. That is why one should not try to stock a southern HBG (or any other fish or southern species CNBG , Fla LMB) into a northern pond. Good quality local ( same climate) fish do better.

BTW thank Dave Wills for the pics. Thanks Dave. bz you can remove a scale and not hurt the fish.