Bycatch

Bycatch, also called by-catch, happens in the fishing industry. It is when fish or other sea animals are caught by mistake while people are fishing for specific kinds or sizes of fish. These animals might be the wrong species, the wrong size, or too young to be caught safely.

Bycatch has been a problem for a long time and can harm many sea animals. It helps cause the decline of some fish groups and can lead to overfishing, where too many fish are caught and the group cannot grow back.

In the United States, scientists estimated that between 1990 and 1999, about 6,215 sea animals like seals and whales were caught by mistake each year. This problem started becoming well-known in the 1960s when dolphins were caught in nets meant for tuna.

Bycatch can include many different animals. Sometimes it is fish that are not the target but are kept and sold. Other times it is fish that are thrown back into the water because they are not wanted. It can also include animals like birds, turtles, and sharks that are caught by mistake. There are ways to estimate how many of these animals can be caught without causing too much harm to their groups.

Activities that produce bycatch

Bycatch happens whenever people fish, and it is not just about catching the wrong kind of fish. Dolphins, sea turtles, and seabirds can also get caught accidentally. This often occurs when using methods like gillnetting, longlines, or bottom trawling. These tools can stretch for many kilometres and catch many animals, including those not meant to be caught.

Shrimp trawling, in particular, causes a lot of bycatch. For every kilogram of shrimp caught, there can be almost six kilograms of other sea creatures. These include small fish, crabs, and other animals that are not wanted. Even with tools designed to reduce bycatch, many animals still get caught and often cannot survive after being released.

Victims

Sharks and rays

Different fishing tools like longlines, trawls, and purse seine nets have put many shark species in danger. These tools often catch young sharks before they can grow up and have families, which makes the problem even worse. Because of this, many shark and ray populations have dropped by more than 70% since 1970.

Cetacean

Main article: Cetacean bycatch

Animals like dolphins, porpoises, and whales can get caught in fishing nets, lines, or hooks. This can happen more and more often. Sometimes, these animals are kept because they can be used as food or bait. For example, dolphins can get stuck in nets used for catching tuna. Since dolphins need to breathe air, they can drown if they stay trapped underwater for too long.

Albatross

See also: Longline fishing

Many albatross birds are in danger because of fishing with longlines. These birds often try to eat the bait on the lines and can get hooked, which leads to their drowning. Each year, around 100,000 albatrosses are affected this way. Unregulated fishing makes the problem even worse.

Sea turtles

Sea turtles, which are already in danger, often get caught in nets used for shrimp. Thousands of Kemp's ridley, loggerhead, green, and leatherback sea turtles are caught each year in the Gulf of Mexico and the US Atlantic. The longer these turtles stay trapped, the higher the chance they will not survive. Sometimes, turtles can escape, but many do not make it out in time.

Mitigation

Concern about catching fish unintentionally has led fishers and scientists to look for ways to reduce this problem. There are two main ways to help.

One way is to stop fishing in areas where too many unintended fish are caught. These areas can be closed permanently, just for a season, or only when a problem happens. Sometimes fishers need to move to a different spot if the problem occurs.

The other way is to use different fishing tools. A simple change is to use nets with bigger holes so smaller fish can escape. This might mean changing the tools they use. There are also special tools called bycatch reduction devices and the Nordmore grate that help fish escape from shrimp nets.

Special tools have been made to help sea turtles escape from fishing nets. These tools, called turtle excluder devices, let turtles and other big animals leave the net through an opening. They work well most of the time but are not perfect.

There are also ways to change how fishing lines are used to help birds avoid getting caught. For example, using bright lines that scare birds away has helped reduce the number of birds getting caught in fishing lines.

Main article: Bycatch

Retention

Sometimes, fishermen keep the fish they catch by accident instead of putting them back in the water. These accidental catches can be used in many ways. In some parts of the world, they are sorted and sold as food. They might be frozen and sold as mixed seafood, or turned into products like fish sauce, fish paste, or fish cakes. They can also be used to feed other fish on farms.

Some places, like Norway, have a rule that fishermen must keep everything they catch. This helps reduce waste and encourages better fishing practices.