‘Radical proposal’ will save ocean life

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An estimated 50 million sharks are caught unintentionally every year. Picture: Helen Bamford

Vancouver - The indiscriminate slaughter of vast numbers of turtles, sharks, albatrosses and other endangered marine animals that get unintentionally caught by fishermen as by-catch, could be prevented by a radical proposal of mobile marine reserves, according to scientists.

Protected areas of the ocean where commercial fishing was banned would work far better if they were not static conservation areas, as they were at present, but were moveable reserves that took into account the mobile nature of sea life, they said.

The proposed conservation zones would not impose fishing restrictions in one place, but would shift location according to where threatened species were expected to be found. The idea has resulted from a revolution in satellite and tagging technology that has allowed scientists routinely to monitor the seasonal movements of marine creatures, which would have been impossible a decade ago.

Scientists said existing marine protection areas, where fishing was controlled to enable wildlife to recover, frequently failed to do their job because the endangered animals simply migrated to unprotected regions where they got caught accidentally.

This is believed to be the main reason that populations of loggerhead and leatherback turtles, both critically endangered, have slumped dramatically in recent years as commercial fishing with nets and extremely long fishing lines has become more intense.

Leatherback turtles have suffered particularly badly in the Pacific Ocean. Sharks and albatrosses have also declined significantly as a result of being caught accidentally by fishermen.

Creating mobile protection areas monitored by satellite would enable some of the world’s most endangered species to recover, as well as allow fishermen to ply their trade in other parts of the ocean where by-catch was less likely, said Larry Crowder, a professor of marine biology at Stanford University in California, in the US.

“Small, stationary reserves do little to protect highly mobile animals, like most fish, like the turtles and sharks and seabirds.

“You might say that the only way to achieve conservation of these kinds of organisms is to protect them everywhere in the ocean,” he said.

“But we don’t need to close the entire ocean; we only need to close the place where they are concentrated,” he told the American Association for the Advancement of Science in Vancouver, Canada.

Satellite tagging and other ways of monitoring the movements of marine creatures have shown that sea life tends to congregate near oceanographic features such as upwellings, where rising currents bring minerals to the sea surface, and convergence zones, where ocean currents collide.

“Those are where everything in the ocean goes to feed, and the fishermen understand that,” Crowder said. These features tend to move, taking sea life with them.

“Satellite technology, tagging and acoustic technology allow us to look into the ocean and figure out who is going where,” he added.

“The time is ripe for the idea of mobile marine protection areas and a good candidate to consider is the North Pacific convergence zone. We know it moves seasonally. In the summer, it’s about 1 000 miles (about 1 600km) north of Hawaii and in the winter, it is further south.”

Several species are threatened. The number of leatherback turtles in the Pacific has declined by 90 percent in 20 years with by-catch a main cause. The loggerhead turtle has been hit particularly hard by shrimp trawling. Albatrosses can become caught on fishing lines and drown. The northern royal albatross is an endangered species.

An estimated 50 million sharks are caught unintentionally every year. The angel shark, vulnerable to by-catch, is now one of the five most endangered shark species. – The Independent

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