i dont think you could tell. its the same genes, unless it wants to be declared by someone that predators would get the majority of the farmed ones if they had been born in the river and its only through farming they survive at all.
sometimes waterways can give off different sheens but they will also change once they are moved. diet, lighting, camoflouge..
for example an ocean bream i catch off the beach is very yellow on the fins and silver on the sides.
yet one i catch in the lake near the ocean has a black sheen on its silver body and the yellow is much less pronounced on its fins. exact same species and not genetically isolated by being in the lake as breeding occurs in the salt when the lake opens. i belive that it is built in fish to slightly alter to their surroundings to sneek up on things or to escape things. a basic part of their gene make up and been with them forever.
same goes with these fish. essentially if you havent brought in new genes from different areas or made progress with selecting for colour (on purpose or not) over a decent number of generations, remember theres only so few young produced, its not as easy to find new colours in so few young and its not like guppies. you need wait years before the selected fish can breed again.
