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Nets Kill Nearly 1,000 Marine Mammals a Day, Group Says

James Owen
for National Geographic News
June 10, 2005
 
Fishing nets intended for other marine species are killing at-risk
species of dolphins and porpoises around the world, according to a
report commissioned by the nonprofit World Wildlife Fund-U.S.

Leading marine scientists ranked dolphins and porpoises across the globe for the risk they face from lethal fishing nets. Ten species are included in a list of populations conservationists say require urgent action to prevent further deaths. The report lists the following priority locations and species:

• Philippines and Southeast Asia: Irrawaddy dolphins

• Zanzibar (East Africa): Indo-Pacific humpback dolphins and Indo-Pacific bottlenose dolphins

• Black Sea: Harbor porpoises

• Philippines: Spinner dolphins and Fraser's dolphins

• Ghana and Togo (West Africa): Atlantic humpback dolphins

• Peru: Burmeister's porpoises

• Argentina, Uruguay, and Brazil: Franciscana dolphins

• Argentina: Commerson's dolphins

Researchers say most of these species are killed by gillnets. Made of monofilament (single-strand) nylon mesh, gillnets are difficult for dolphins and porpoises to see or detect with their sonar.

Once entangled in netting or its supporting ropes, marine mammals face high risk of drowning. Driftnets and crab nets can also kill the mammals. Nontarget species accidentally caught in fishing equipment are known as bycatch.

"Almost one thousand whales, dolphins, and porpoises die every day in nets and fishing gear," said Karen Baragona, of the WWF species-conservation program.

The new report will be submitted to the International Whaling Commission (IWC) at its annual meeting next week in South Korea.

Last year the U.S. Commission on Ocean Policy identified bycatch as the greatest global threat to cetaceans (whales, dolphins, and porpoises). Marine experts estimate that more than 300,000 cetaceans are killed by fishing gear every year.

Randall Reeves, lead author of the WWF-U.S. report, chairs the World Conservation Union's Cetacean Specialist Group, based in Gland, Switzerland. He says the study team focused on identifying cetacean species or populations most likely to end up as bycatch—especially those where the prospect of successful mitigation measures appeared good.

Conservation Guidance

"It's crucial to give guidance to agencies and organizations on how they should invest their resources," Reeves said.

Baragona, of the WWF-U.S., says accidental dolphin and porpoise deaths can be significantly reduced, often with simple, low-cost solutions.

"The United States and several other countries have significantly reduced bycatch in their waters," she noted. "Slight modifications in fishing gear can mean the difference between life and death for dolphins."

Species on the bycatch priority list include the Irrawaddy dolphin. Globally threatened, the marine mammal has at least two populations that are listed as critically endangered by the IUCN.

The dolphin's last known haunt in the Philippines is Malamapaya Sound, where only around 77 individual dolphins remain. Study co-author Brian D. Smith, of the New York-based Wildlife Conservation Society, says the population's decline is almost certainly due to crab fishing.

Smith said a positive step would be to develop more efficient crab pots as an alternative to nets, which ensnare and kill Irrawaddy dolphins. He and his colleagues also recommend closing some Irrawaddy dolphin habitats to gillnet fishing.

In addition, data suggest that thousands of harbor porpoises are killed annually in the Black Sea by gillnets set for turbot, sturgeon, and dogfish.

In 2003 the International Whaling Commission indicated that existing fisheries regulations for the Black Sea were not being enforced. The WWF report recommends assisting Black Sea nations, such as Ukraine, to tackle illegal fishing.

In the case of Atlantic humpback dolphins, the report's authors have little idea how many of the animals remain or how many die as bycatch. The coastal species is found only in West Africa. Some Atlantic humpback dolphin populations are known only by a single specimen.

Lack of Data

In Ghana, West Africa, tens of thousands of coastal residents earn their livelihood from the sea. Because of this, researchers say, gillnet closures are unlikely. They add that little has been done to safeguard dolphins in the region, mainly because a lack of data has left regional governments unconvinced that stocks are severely depleted.

In other parts of the word, measures to reduce levels of cetacean bycatch are thought to be working. In U.S. waters, for example, gillnets are now prohibited in some coastal areas. Pingers (acoustic deterrents that warn or scare dolphins, porpoises, and whales away from fishing nets) are mandatory in other areas.

In European Union waters, the use of drift nets for tuna in the Atlantic and Mediterranean was banned in 2002. All other drift-netting will be phased out by 2008. Pingers are also becoming mandatory for all E.U. gillnet fisheries.

It's the fate of dolphins and porpoises in the developing world that most concerns conservationists, especially because these waters support the greatest number of cetacean species and the most at-risk populations. The WWF report says fisheries in the developing world "tend to be small-scale and decentralized, making assessment, monitoring and conservation intervention difficult."

Baragona, of WWF, says developing nations must recognize they have a problem and make change a priority. She also calls for better data on fisheries by these countries: "How many boats? What type of gear? What are they targeting? How much bycatch are they landing?" She adds that better enforcement of fishing regulations and increased monitoring of cetaceans is also needed in developing nations.

Baragona says that, around the world, fishing gear that traps marine mammals needs to be replaced.

"A more cutting edge approach is to use nets infused with barium sulfate, which makes them stiffer [and thus less likely to tangle] and easier [for marine mammals] to detect acoustically [for example, with sonar]," she said. This technology could possibly be "combined with materials that make the nets glow in the dark underwater, so the animals can see them," she added.

In April WWF awarded a prize for a fishing net design incorporating such dolphin-friendly features.

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