Dolphin killed by pair-trawling. Thousands of porpoises and dolphins die every year as accidental bycatch.

Bycatch

Many fisheries catch fish other than the ones that they target and in many cases these are simply thrown dead or dying back into the sea. In some trawl fisheries for shrimp, the discard may be 90 percent of the catch. Other fisheries kill seabirds, turtles and dolphins, sometimes in huge numbers.

Estimates vary as to how serious a problem bycatch is. Latest reports suggest that around eight percent of the total global catch is discarded, but previous estimates indicated that around a quarter of might be thrown overboard. Simply no-one knows how much of a problem this really is.

The incidental capture, or bycatch, of mammals, sea-birds, turtles, sharks and numerous other species is recognised to be a major problem in many parts of the world. This figure includes non-target species as well as targeted fish species that cannot be landed because they are, for instance, undersized. In short, anywhere between 6.8 million and 27 million tonnes of fish could be being discarded each year, reflecting the huge uncertainties in the data on this important issue.

The scale of this mortality is such that bycatch in some fisheries may affect the structure and function of marine systems at the population, community and ecosystem levels. Bycatch is widely recognised as one ofthe most serious environmental impacts of modern commercial fisheries.

The victims

Different types of fishing practices result in different animal/species being killed as bycatch: nets kill dolphins, porpoises and whales, longline fishing kills birds, and bottom trawling devastates marine ecosystems.

It has been estimated that a staggering 100 million sharks andrays are caught and discarded each year. Tuna fisheries, which in thepast had high dolphin bycatch levels, are still responsible for the death of many  sharks. An estimated 300,000 cetaceans (whales, dolphins and porpoises) also die as bycatch each year, because they are unable to escape when caught in nets.

Birds dive for the bait planted on long fishing lines, swallow it (hook included) and are pulled underwater and drowned. Around 100,000 albatrosses are killed by longline fisheries every year and because of this, many species are facing extinction.

Bottom trawling is a destructive way of 'strip-mining' the ocean floor, harvesting the species that live there. As well as the target fish species, this also results in bycatch of commercially unattractive animals like starfish and sponges. A single pass of a trawl removes up to 20 percent of the seafloor fauna and flora. The fisheries with the highest levels of bycatch are shrimp fisheries: over 80 percent of a catch may consist of  marine species other than the shrimp being targeted.

Technology

Many technical fixes exist to reduce bycatch. Turtle exclusion devices are used in some shrimp fisheries to avoid killing turtle species. In the case of longline fisheries, the process of setting the hooks can be changed and bird-scaring devices employed which radically cut the numbers of birds killed. To avoid dolphins being caught in nets other devices can be used. Pingers are small sound-emitting and dolphin-deterring devices that are attached to nets, but they are not always effective. Escape hatches (consisting of a widely spaced metalgrid, which force the cetacean up and out of the net) have also been used.

Although these devices may have a role to play, they cannot address the whole problem. Such devices need continual monitoring to check how well they work and assess any potential negative effects they may have. Realistically they will probably only be used in areas with well-developed fishery management and enforcement agencies.

On a global level, probably the only effective way to address the problems of bycatch is to control fishing effort. This will be best achieved through the creation of marine reserves. Nonetheless, in the case of highly mobile species such as seabirds and cetaceans, the only effective way of preventing bycatch is to discontinue the use of particularly damaging fishing methods.

The latest updates

 

A 'ray of hope' for the oceans

Feature story | August 30, 2006 at 6:00

Apo Island Marine Reserve in central Philippines is a 'ray of hope' for oceans around the world, Greenpeace said today during the visit of the ship MY Esperanza to the famous reserve. The Esperanza was welcomed in pristine Apo Island by the local...

An “Angel” to Defend our Oceans

Feature story | August 29, 2006 at 6:00

Angel Aquino is no stranger to the limelight. She has always been a favorite cover girl of various magazines. Starting out as a model, she later became a successful film actress and lifestyle television host. Angel is now a Greenpeace Ocean...

Whale sharks spotted in Bigaa, Legaspi City

Feature story | August 27, 2006 at 6:00

The recently-discovered presence of feeding whale sharks in the Albay Gulf, particularly along Legaspi City’s coastline, only confirms the urgent need to defend the rich coastal waters of the Bicol region from threats like mining pollution,...

Compelling evidence of toxicity in Rapu Rapu

Feature story | August 24, 2006 at 6:00

There is no doubt that toxic pollution from the mine would clearly affect the coastal and marine ecosystems of Rapu-Rapu Island. Therefore, Lafayette's mining operations in Rapu Rapu must be permanently shut down.

ABN AMRO & ANZ: Stop funding marine pollution

Feature story | August 23, 2006 at 6:00

After helping mitigate the devastation wrought by the Petron oil spill in Guimaras Island, the Esperanza led a flotilla in protest against the gold and silver mining operations of Lafayette in the Philippines, funded by banks such as ABN-AMRO and...

Stop the mine! Save our seas!

Feature story | August 23, 2006 at 6:00

Like a ticking clock in a time bomb that’s set to go ‘boom!’ The reopening of the Lafayette mine has started the countdown for another disaster in our marine ecosystem.

Philippines spill witnessed first hand

Feature story | August 22, 2006 at 6:00

It took Rodolfo Galuna only 15 days to build the small wooden boat he named "Rona". But now the 52-year-old fisherman has no use for it. Black, stinking oil sludge covers the boat’s hull, has crept into Galuna's back yard and quietly destroyed...

Devastation at ground zero

Feature story | August 20, 2006 at 6:00

Scientists and environmental activists onboard the Esperanza today bear witness to the site of the Petron oil spill in order to document environmental impacts of the oil slick in the Guimaras Strait of the central Philippines.

Philippines oil spill

Feature story | August 19, 2006 at 6:00

Today, Joaquin Nava, the Governor of the Philippine island hardest hit by a 350,000 litre oil spill, issued a desperate plea for help: "We can only watch in horror how an oil spill can undo in a few days our initiatives which have taken...

Rubbish at the Bay

Feature story | August 16, 2006 at 6:00

The plastic waste survey and documentation undertaken today by Greenpeace and Eco-Waste Coalition highlights the urgency of implementing waste management laws on land, particularly those concerning plastics such as disposable (single-use)...

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