People have been fishing for thousands of years, to feed their families and local communities. Today, however, many kinds of fish are in danger of disappearing forever.

New ways of fishing have been shrinking fish populations around the world. Fishers remove more than 77 billion kilograms (170 billion pounds) of fish and shellfish from the sea each year. If they continue to fish as they do now, they may soon wipe out many kinds of fish, scientists say. To stop this from happening, fishers need to start using sustainable fishing practices.

Sustainable fishing is a way of fishing responsibly. It kills fewer fish, and keeps fish populations at healthy levels. If the world's fishers switch to sustainable fishing, there will always be enough fish in our oceans, lakes and rivers.

The danger facing the world's fish is very serious. Consider the example of the bluefin tuna. High demand for this tasty fish has greatly reduced its population. Today, there are only around one-quarter as many spawning bluefin tuna as there were in 1970. Tuna and other fish only spawn, or release eggs, when they reach a certain age.

Since around 1970, fishers have been catching bluefin tuna in two harmful ways. One is purse seining. The other is longlining.

Purse seine fishing first uses a net to herd fish together. It then traps them by pulling the net's drawstring. The net can scoop up many fish at a time. It is mostly used to catch fish traveling in large groups known as schools, or fish that come together to spawn.

Longlining is a type of fishing in which a very long line is dragged behind a boat. These lines can be up to 100 kilometers (62 miles) long. They have thousands of baited hooks.

Both purse seining and longlining can catch hundreds or thousands of fish at a time.

Overfishing

Over time, these types of fishing can leave few fish in the ocean. If a fish population becomes too small, it cannot easily replenish itself, or grow back to its original size. Fish populations replenish through reproduction, or the birth of new fish through spawning.

Taking wildlife from the sea faster than populations can reproduce is known as overfishing. Purse seining and longlining both lead to overfishing. They also result in bycatch. A bycatch is something that is caught by accident. For example, longlines meant for bluefin tuna (Thunnus thynnus) also catch other fish, such as swordfish (Xiphias gladius). They can also trap birds and sea turtles.

Chilean seabass (Dissostichus eleginoides) is another fish that has been overfished. During the 1990s, Chilean seabass became very popular in restaurants. Over time, the seabass population shrank and most seabass that were caught were small. Chilean seabass is a long-lived, slow-growing fish. Most smaller fish are too young to have spawned. As fishers caught more smaller seabass, healthy replenishment of the population became unlikely. More and more young fish never grew old enough to spawn.

Today, Chilean seabass are still facing overfishing.

Sustainable Fishing Practices

There are ways to fish sustainably. Such practices allow us to enjoy seafood while making sure that fish populations remain for the future. In many traditional cultures, people have fished sustainably for thousands of years. Today's sustainable fishing practices reflect some lessons learned from these cultures.

For example, the Tagbanua people of the Philippines have traditionally used fishing practices that keep fish populations at a healthy size. They continue to follow these practices today. The Tagbanuas fish for specific kinds of fish only during certain times of the year. The rest of the year, these fish populations are given time to replenish themselves.

The Tagbanuas also set aside certain areas as protected spots in which fishing is never allowed. When they do fish, they catch only what they need to feed themselves and their communities. They primarily use hook-and-line fishing.

If you have ever gone fishing, you probably used a rod and reel. Rod-and-reel fishing is a modern version of traditional hook-and-line. It results in less bycatch because fish you weren't planning to catch can be released immediately. Additionally, only one fish is caught at a time, preventing overfishing. Rod-and-reel fishing is much more sustainable than longlining.

Another way to help prevent overfishing and bycatch is to stop eating fish. Ocean scientist Sylvia Earle has taken that step. She believes people need to take a break from eating seafood until we stop overfishing.

"I personally have stopped eating seafood," Earle says. "I know too much. I know that every fish counts at this point." Fish are very important to the health of our oceans, which in turn "make the planet work," Earle says.

Of course, many of us will want to keep on eating fish. If we do, we should try to choose seafood from sustainable fisheries. To do that, we first need to educate ourselves about where our fish comes from and how it is caught. Knowing more will help us make the best choices for our ocean's future.