Do Fish Burp??

I've decided to keep my blogs lighter, so here goes...

Do fish burp? I know, fish don't swallow air so they don't really burp from that, but most burping really is caused by the process of digestion - the enzymes, and bacteria in your body that give off air when digesting. I tried to google this but couldn't find the answer. Guess I'll be watching my aquarium more carefully.