When you catch a fish that has 2 or 3 on the line, it is still 1 fish.
That sounds like something that someone who's addictied to smoking would say when they're smoking 3 cigarettes at the same time. "I'm smoking them all at the same time so it's only 1, right?"
But yea, just pickin lol.
It just seems like a bad choice of words to say the cap is '200 fish'. It seems like it would be better to say '200 catches'.
If you were fishing something that you can get multiples of and you ended up with 248 fish after 200 catches and someone asked 'how many fish do you have in your inventory right now?' you would say 248, not 200.