my mate has black bream in his dam now for well over 10 years and they have bred in his dam and have evolved as well having a longer snout then a standard black bream and tail is bit different as well... i have tried to get some small ones off him but hes a hoarder of everything not just fish..... may have to sneak over when hes away on holiday and try and catch a few i have eaten some when over his place and taste superb.... totally fresh water - definitely not a drop of salt water in the dam...
i'd like a fish species that survives winter and summer and also breeds in your aquaculture setup and doesnt eat its own fry ???
redfin perch has a bit of appeal but i'd imagine they would eat their own fry... and i'd expect fisheries prob wouldnt approve....