When people go out fishing, they often have something specific in mind, but it's very difficult to catch only what you're looking for. Pulling a net through the water or across the sea floor catches all the animals in its path, not just the tasty fish, and can destroy important ecosystems. Baited hooks attract seabirds, sharks and other animals along with the big tuna or swordfish that are being sought. Even if animals are able to survive being caught in a net and are thrown back overboard, many still die. Some nets and traps are “lost” but continue to kill, a phenomenon called ghost fishing.
All the animals that are caught unintentionally are called bycatch, and it's an enormous waste of ocean resources and animal life. Some species are especially vulnerable to being killed accidentally by fishing activities and are threatened with extinction. Around the world, governments are working to develop methods to reduce bycatch.