If something resembles fish, in taste or odor we say it's "fishy". A fishy smell. etc.
It can also mean a cold or expressionless look. "A fishy stare." etc.
But if we say something is "fishy" it means it inspires doubt or suspicion.
Of course there's something fishy about this picture, because the man is holding a net full of fish.
Personally I think he looks fishy. Would you buy fish from him?