Bycatch

Bycatch, also called by-catch, is a word used in the fishing industry. It means fish or other sea animals that are caught by mistake when fishermen try to catch certain kinds or sizes of fish. These accidental catches might be the wrong kind of animal, the wrong sex, or too small to keep, like young animals called juveniles.

People have known about bycatch for many years. It can help fish numbers go down and is part of something called overfishing. A famous example happened in the 1960s when dolphins were caught by accident in nets meant for tuna.

The word “bycatch” can be used in different ways. It might mean fish that are sold but not the main target, fish that fishermen let go, any fish not meant to be caught, or even animals like seabirds, sea turtles, and sharks. There are tools to help limit bycatch so animal groups stay safe.

Activities that produce bycatch

Bycatch happens when fishing takes place. It isn’t just fish that can get caught by accident — dolphins, sea turtles, and seabirds can also become bycatch. The most common fishing methods that cause bycatch are gillnetting, longlines, and bottom trawling. These tools can stretch for many kilometers and catch many animals.

Shrimp trawling is especially known for bycatch. Even with tools designed to reduce bycatch, many animals like fish and crabs are still caught accidentally and often cannot survive. Bycatch isn’t limited to fishing — it can also happen when scientists or pest controllers set traps, sometimes catching unintended creatures instead.

Victims

Sharks and rays

Different fishing tools like longlines, trawls, and purse seine nets have put many shark species in danger. Young sharks are also often caught by accident, which can affect how many new sharks are born. 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. Sometimes they are kept to be used as food or bait. For example, dolphins can drown when caught in tuna nets because they need to breathe air, unlike fish that can breathe underwater. This problem has led some tuna to be labeled “dolphin friendly,” though this only means the dolphins were not specifically targeted.

Albatross

See also: Longline fishing

Many albatrosses are threatened because they get caught on longline fishing hooks while looking for food.

Sea turtles

Main articles:

Sea turtles are also often caught in shrimp trawl nets. Different kinds of sea turtles are caught more in different places, like Kemp’s ridley turtles in the Gulf of Mexico and loggerhead turtles along the US Atlantic coast.

Mitigation

People worry about bycatch, so fishers and scientists look for ways to catch fewer unwanted animals. There are two main ways to help.

One way is to stop fishing in places where too much bycatch happens. These breaks can be permanent, for a season, or just for a short time when there is a problem. Fishers might need to move to a different area if bycatch becomes an issue.

The other way is to use different fishing tools. A simple way is to use nets with bigger holes so smaller fish can escape. Some tools, like bycatch reduction devices and the Nordmore grate, help fish get out of shrimp nets.

These devices help many fish escape, but they do not work perfectly for every species. New tools, like SharkGuard, show promise in reducing the catch of sharks and rays.

Seabirds can also get caught on longlines. Using bright, flapping lines called streamer lines near longlines scares seabirds away, helping to protect them.

Retention

Some fisheries keep bycatch instead of throwing it back into the ocean.

Bycatch can be sorted and sold as food, especially in Asia, Africa, and Latin America. It may be sold frozen as "assorted seafood" or used to make fish hydrolysate for organic agriculture, fish meal, fish paste, or surimi. In Southeast Asia, bycatch is sometimes used to make fish sauce. It can also be given to fish farms to feed other fish.

Norway has a "no discards" policy, meaning fishermen must keep everything they catch. This policy has helped reduce waste and encouraged research and changes in fishing habits.