They could recycle if they wanted to. The reason they serve the fish head is to gross you out, and stop you spending all night in the restaurant, when there are people waiting. But, instead of leaving early to go home and hurl, why not tell all your friends these Fun Fish Facts. Fish live in water. Fish actually breathe water, like Aquaman.
Fish can swim from as soon as they're born.
Fish eat other fish, except for the vegetarian fish. Sardines naturally grow in tins. The way the lid cuts you is part of their natural defence mechanism. Oysters aren't fish, but live in the sea, and taste a bit like swallowing your own phlegm. If every fish in the world was called Eric, there'd be no way to tell them apart.