Definitely a sturgeon, but come on now, thats not good enough for MFK, people.
I can say with some confidence this is a russian sturgeon. Other candidates are starry sturgeon or sterlet sturgeon, but the scute arrangement does not appear sterlet to me. The kicker: even though we cant see the snout (best way to differentiate sturgeon), i can see its shadow which appears blunt and short, definitely not long and thin like a starry.
Could be some lesser known primarily freshwater species, maybe sakhalin, im certainly no expert, but i would put my money on a subadult russian sturgeon aka ossetra.