it poops like a boy
No. A fish's body is naturally buoyant to allow it to float at a certain level in the water. Saltwater is more dense (because of the salt), which makes a fish more buoyant. A freshwater fish, swimming in saltwater, will float too high in the water, and it will die from struggling to keep itself at a deeper water level.
Doesn't do much just makes them stop moving for a sec. but the fish still live.
the quills are prickley and it makes itself look bigger.
in the jaw
In the same way your skin repairs itself. It has evolved genetically to be able to repair the external damage that happens occasionally.
Yes, undercooked fish makes your stomache upset, especially if it wasn't properly cooked or taken care of before you ate it. You probably have food posioning.
The parrot fish
It eats any other fish smaller than itself. With it's very fast swimming it also makes it very easy for it to injure another fish then eat it. It does not have teeth but swallows it.
A Plecostomus can live by itself.
uh... because it is a fish.
A fish which happens to be particularly large.
ARMAGEDDON!