For thousands of years, people have fished to feed their families and local communities. Today, however, many fish populations are severely threatened. Many kinds of fish may soon disappear.

Ever-growing demand for seafood and new ways of fishing have led to shrinking fish populations around the world. Fishers remove more than 77 billion kilograms (170 billion pounds) of marine life from the sea each year. Scientists fear that continuing to fish at this rate may soon wipe out many kinds of fish. In order to stop this from happening, fishers need to start using sustainable fishing practices.

Sustainable fishing is a way of fishing that allows fish populations to remain at healthy levels. It ensures there will always be enough fish in our oceans, lakes and rivers.

The threat facing the world's fish is very serious. Consider the example of the bluefin tuna. High demand for this fish has threatened its population. Today, there are only around one-quarter as many spawning bluefin tuna — those releasing eggs — as there were in 1970.

Since around 1970, commercial fishers have caught bluefin tuna using two methods that cause a great deal of harm. One is purse seining, and 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 typically 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 set and dragged behind a boat. These lines can be up to 100 kilometers (62 miles) long and have thousands of baited hooks.

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

Overfishing

For fishers, catching so many fish at once is very profitable. However, over time this type of fishing leaves few fish left 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 a lot of bycatch. A bycatch is something that is accidentally or unintentionally caught. For example, longlines intended to catch bluefin tuna (Thunnus thynnus) also catch other fish, such as swordfish (Xiphias gladius). In addition, they can trap birds and sea turtles.

Chilean seabass (Dissostichus eleginoides) is another fish species that has been overfished. During the 1990s, Chilean seabass became very popular in restaurants. Over time, the seabass population shrank and a larger proportion of them that were caught were small. Chilean seabass is a long-lived, slow-growing fish. Most smaller seabass are young, and may not have spawned yet. As fishers caught more smaller seabass, healthy replenishment of the population became unlikely, because more and more young fish never grew old enough to spawn.

Today, Chilean seabass are still facing overfishing.

Overfishing also occurs with freshwater fish. One example is the beluga sturgeon (Huso huso), a large, slow-growing fish. Beluga sturgeon can grow up to 4.5 meters (15 feet) and 1,135 kilograms (2,500 pounds). They take about 20 years to reach maturity, at which point females release their eggs, which are called roe. However, they only spawn every three to four years. Beluga sturgeon are best known for their roe, which is also called caviar. In fact, Caspian Sea sturgeon are the source of about 90 percent of the world's caviar. The fish are slow-moving and easy prey for fishers. When their eggs are harvested, the fish cannot maintain their populations.

Today, the Beluga sturgeon population continues to decline.

Sustainable Fishing Practices

There are ways to fish sustainably. Such practices allow us to enjoy seafood while ensuring that 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.

In the Philippines, for example, the Tagbanua people have traditionally used fishing practices that maintain fish populations. They continue to follow these practices today. The Tagbanuas fish for specific species only during certain times of the year, allowing fish stocks to replenish themselves. They also set aside certain areas as protected spots in which fishing is forbidden. When they do fish, they catch only what they need to feed themselves and their communities. They primarily use hook-and-line methods.

If you have ever gone fishing, chances are you used a rod and reel. Rod-and-reel fishing is a modern version of traditional hook-and-line. Rods and reels come in different shapes and sizes, allowing fishers to target a wide variety of fish species. Rod-and-reel fishing results in less bycatch because non-targeted species can be released immediately. Additionally, only one fish is caught at a time, preventing overfishing. For commercial fishers, who make their living from fishing, rod-and-reel fishing is a more sustainable alternative to longlining.

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

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

Those of us who continue to eat fish should try to choose seafood from sustainable fisheries. To do so, we should educate ourselves about where our fish comes from and how it is caught. Resources such as the Seafood Decision Guide can help us make the best choices for our ocean's future.