Saltwater fish, also called marine fish or sea fish, are fish that live in seawater. Saltwater fish can swim and live alone or in a large group called a school.
Saltwater fish live in the ocean. For example, the butterfly kingfish lives in the ocean. This ray-finned fish has had many common names, including big-scaled mackerel, bigscale mackerel, common gasterochisma, gasterochisma, butterfly mackerel, butterfly tuna, pachycormid, little pachycormid, scaled tunny, scaly tuna, and others.
Overfishing is the most common cause of fish declining. Not too many of us are overfishing, since most coral reefs are protected. However, since fish is a popular food, we are trying to catch fish with nets.