The causes of overfishing can be put into these three categories:

Overcapacity:

All over the world, many fishing industries have large vessels, equipment, and technology that they can deploy deep into the oceans. They can stay on the seas for weeks and months and even process the fish before they come back ashore. Experts believe that all the world’s equipment combined is enough to fish on four Earth-like planets.

Unsustainable Fishing:

It involves using nets, fishing methods, and other equipment that catch too much fish to a degree that they are endangered. It also involves catching other sea animals other than fish in the process. These are called By-catch. In many cases, by-catch is destroyed and thrown back into the sea. This is called Discards and may include cetaceans, turtles, sharks, seabirds, young fish, corals, and invertebrates like starfish, crabs, sea urchins, brittle stars, mollusks, sponges, and worms. They also catch young fishes and prevent them from growing to reproduce.

Some fishing methods like Bottom Trawling are known to catch all kinds of fish and animals, with the bulk of it discarded.

Economic and Food Needs:

The amount of fish that fishing industries bring ashore depends on the market and needs of consumers. In the past century, humans have multiplied in many folds, and the need for food and fish has also multiplied. That, together with the economic ambitions of fishing industries has forced them to catch more fish than the oceans can replace.

Now, let us quickly take a look at some very important terms before we go further into the problems that overfishing causes.