What Is the Definition of Marine Bycatch?

Protecting Marine Life With Safe Fishing Practices

Marine bycatch is a term that describes animals caught unintentionally by fishing gear, including non-target species and undersized fish. It can also include marine mammals, which are commonly highlighted in the media as being threatened by fishing practices. 

When they are at sea, many fishermen seek to catch a "target" species. When fishermen catch something that they didn't intend to, such as a different fish species, a cetacean, sea turtle or seabird, that is called bycatch.

Why Bycatch Matters In the Environment

Bycatch is a huge problem in some fisheries. Prior to the 1990s and improvements in the yellowfin tuna fishery, hundreds of thousands of dolphins were caught in purse seine nets each year. Bycatch is not only a problem for environmentalists and resource managers. It is a problem for fishermen because bycatch can damage fishing gear and cause losses in fishing time. When extra species are caught, fishermen need to spend extra time separating bycatch from their intended species. In many cases, bycatch needs to be thrown back, and in some cases, the animals are already dead when they are returned to the ocean. In the past, some fishermen just let the bycatch die on purpose not realizing how important the creatures were. 

How much bycatch is going on, and is it really a problem? According to a 2005 study by the Food and Agricultural Organization of the United Nations, the estimated global bycatch is about 8 percent of the total catch.

The Consortium for Wildlife Bycatch Reduction reports that about 7.3 million tons of marine life are caught incidentally each year. In some cases, the amount of bycatch is more than the intended species. A freshwater porpoise, the baiji, that was only found in China’s Yangtze River, is believed to be extinct ​to relentless fishing and hooking practices.

Populations of another porpoise found in Mexico’s Gulf of California has declined to just several hundred animals due to nets that entangle and kill the animals. The North Atlantic right whale is also in trouble due to fishing practices, and there are just about 400 of them on the plant. 

Solutions to Bycatch

Over the years, scientists and fishermen have been working to resolve the bycatch problem. They realize that the impacts of bycatch are both harmful to the environment and their profit margins. This work has resulted in a great reduction in bycatch in some fisheries, such as the reduction of sea turtle bycatch after fishermen were required to install turtle excluder devices (TEDs) in their nets. Bycatch is still a problem, particularly in areas were there is a lack of funding or enforcement occur. Some fishing organizations do not have -- or do not care to -- invest in proper fishing techniques or equipment to reduce bycatch.