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.

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.

In the United States, scientists found that sea animals like seals and whales were sometimes caught by mistake. This problem became known 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. 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.

Activities that produce bycatch

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

Shrimp trawling, in particular, causes a lot of bycatch. For every kilogram of shrimp caught, there can be many other sea creatures caught too. These include small fish, crabs, and other animals that are not wanted. Even with tools designed to help reduce bycatch, many animals still get caught.

Victims

Sharks and rays

Fishing tools like longlines, trawls, and purse seine nets catch many sharks. These tools often catch young sharks before they can grow up and have families. Because of this, many shark and ray populations have dropped a lot 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 often. Sometimes, these animals are kept to be used as food or bait. For example, dolphins can get stuck in nets used for catching tuna. If dolphins stay trapped underwater too long, they can drown because they need to breathe air.

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. This can lead to their drowning. Unregulated fishing makes the problem worse.

Sea turtles

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

Mitigation

People worry about catching fish by mistake. Fishers and scientists work together to make this happen less. There are two main ways to help.

One way is to not fish in places where too many fish get caught by mistake. These places can be closed forever, just for a short time, or only when there is a problem. Sometimes fishers need to go to a different spot if this happens.

The other way is to use different fishing tools. A simple change is to use nets with bigger holes so small fish can get away. This might mean using new tools. There are special tools called bycatch reduction devices and the Nordmore grate that help fish get out of shrimp nets.

Special tools have been made to help sea turtles get out of fishing nets. These tools, called turtle excluder devices, let turtles and other big animals leave the net through a hole. 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 not get 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 fish they catch by accident instead of putting them back in the water. These fish can be used in different ways. In some places, they are sold as food. They might be frozen and sold as mixed seafood, or made into things like fish sauce, fish paste, or fish cakes. They can also be used to feed 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.