do fishes pass gas like animals?

Fish 'are' animals and yes they pass gaseous waste along with solids through excretion just as other animals do.

They release gas as it's produced, in too small of quantities to be noticeable. They don't store it up to release all at once like mammals do.

Of course- all animals have to, otherwise the gases would build up to dangerous levels inside the body and poison them.

No. Flatulence is a mammalian trait only. Fish can't do this but they do take poops!