What sea animals are scavengers?

not all fish are scavengers mostly just bottom feeders, like tilapia, catfish, and even starfish. That is one of the reasons I won't eat store bought tilapia, most of them come from growers, who raise them in tanks with other fish like cod (not certain if it is cod or whitefish). Then the only food the tilapia gets to eat is the left over cod food and the poo.