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Bycatch

Overview

Wherever there is fishing, there is bycatch—the incidental capture of non-target species such as dolphins, marine turtles and seabirds. Thousands of miles of nets and lines are set in the world's oceans each day. Modern fishing gear, often undetectable by sight and extremely strong, is very efficient at catching the desired fish species—as well as anything else in its path. A staggering amount of marine life—including turtles, dolphins and juvenile fish—is hauled up with the catch, and then discarded overboard dead or dying.

Fishing industry leaders increasingly realize the need to reduce this phenomenon. Proven solutions do exist, such as modifying fishing gear so that fewer non-target species are caught or can escape. In many cases, these modifications are simple and inexpensive, and often come from fishers themselves.

Despite new technologies and industry recognition of the issue, bycatch is still a major problem. Not only does it cause avoidable deaths and injuries, but the fishing methods can be harmful to the marine environments where they are employed. WWF aims to reduce bycatch by working with fisheries and helping develop and promote new technologies and gear for more efficient operations.

Marine Turtles Bycatch

Marine turtle bycatch.

Irrawaddy Dolphins: The Smiling Faces of the Mekong

Irrawaddy dolphins are an unusual species with small populations found in Southeast Asia. WWF works with local communities to develop fishery management zones to help sustain the fish population and conserve the species.

dolphin jumping

Causes

Bycatch - bottom trawler

Here a bottom trawler scrapes the ocean floor destroying the habitat, Baja California, Mexico.

Bycatch occurs because modern fishing gear is very efficient, often covers an extensive area, and can be highly unselective—it catches not only the target species but many other marine animals as well. Poor fisheries management in certain countries further contributes to the problem. Widespread pirate fishing ignores regulations on net mesh sizes, quotas, permitted fishing areas and other bycatch mitigation measures.

NON-SELECTIVE FISHING GEAR
Fishing gear is largely non-selective—any species can be caught, including non-target species. Longlines, trawling and the use of gillnets are the fishing methods that most commonly result in bycatch. Longlining is a commercial fishing method commonly targeting swordfish, tuna and halibut, where hundreds or thousands of baited hooks hang at intervals along a single fishing line. The hooks (commonly called “J hooks”) cause problems for marine turtles when swallowed, usually resulting in death. Sharks, non-target billfishes and juvenile tunas are often hooked as well.

With trawling, boats drag large nets along the seabed, catching almost everything in their path. They can damage coral reefs and at shallow depths, catch marine turtles. Gillnets are mesh nets that allow fish to pass their heads and gill coverings through a hole in the mesh and then get stuck when they try to back out. They can be several miles long and up to 100 feet deep. Bycatch occurs because the nets also trap everything larger than the net’s mesh, which includes juvenile fish, sharks, seabirds, marine turtles and cetaceans (whales, dolphins, porpoises). The nets are very hard to see, blending in perfectly with the water and difficult for cetaceans to detect by echolocation. Gillnets that are lost at sea are rarely recovered and can continue to capture marine animals for many years.

Impacts

Unsucceful attempt by a diver to rescue a Leatherback turtle caught in a net

Diver trying to rescue a leatherback turtle caught in a net.

It is estimated that over 300,000 small whales, dolphins, and porpoises die from entanglement in fishing nets each year, making this the single largest cause of mortality for small cetaceans. Species such as the vaquita from the Gulf of California and Maui’s dolphin from New Zealand face extinction if the threat of unselective fishing gear is not eliminated.

Hundreds of thousands of endangered loggerhead turtles and critically endangered leatherback turtles drown annually on longlines set for tuna, swordfish, and other fish. Incidental capture of turtles by longlines, trawls and gillnets is the single greatest threat to the survival of most populations.

What WWF Is Doing

Green Turtle

Here a green turtle that was accidentally caught in fishing gear is about to be returned to the wild by WWF staff.

Proven solutions do exist to reduce bycatch and others are being discovered. WWF and its partners are working to develop, test, and implement alternative fishing gear and to integrate conservation science into effective fisheries management. WWF and its partners are also working to strengthen legislation on bycatch and to raise consumer awareness about sustainably caught fish.

INSPIRING INNOVATION

Bycatch mortalities can often be reduced by modifying fishing gear so that fewer non-target species are caught or so that non-target species can escape. In many cases, these modifications are simple and inexpensive. WWF created the International Smart Gear Competition to promote the development of such innovative technology. WWF offers more than $50,000 in prize money to attract new ideas that may prove to be a valuable solution to some of the most pressing bycatch problems in fisheries around the globe. Winning entries have resulted in effective solutions to prevent bycatch of marine turtles and seabirds and have even been implemented by the recreational fishing industry

ALTERNATIVE GEAR

Loggerhead Turtle

WWF works with partners to introduce “circle” hooks. These hooks are far less likely to be swallowed by turtles than J-shaped hooks, which cause suffocation or internal bleeding when ingested. Working with the Inter-American Tropical Tuna Commission (IATTC) and other partners, we introduced the hook in eastern Pacific longline fisheries. As a result, marine turtle deaths may be reduced by as much as 90 percent without adversely affecting catches of swordfish and tuna.

In the Coral Triangle, WWF works with longline tuna fishing vessels to convert traditional hooks to circle hooks, which can maintain or even increase fish catches while decreasingturtle bycatch. Preliminary trials were a tremendous success, and WWF hopes to expand the program to all longline vessels in Papua New Guinea and Solomon Islands, helping to protect vulnerable populations of marine turtles and sharks while supporting local livelihoods.

In the Gulf of California, we've been working with partners on ways to reduce the threat of accidental vaquita capture. So far, a different type of trawl net has been developed and pilot tested. It contains an excluder device to reduce vaquita bycatch while still effectively catching shrimp.

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