Ocean 'road' safety key to survival

Posted: 14 February 2004

Tim Radford in Seattle learns how fishing endangers marine life.

Marine scientists want to create "mobile" marine reserves for the giant predators of the ocean, ensuring fishermen avoid ever-shifting safety zones in the Gulf Stream, or the Antarctic convergence, so that turtles, tuna, sharks and the wandering albatross, can congregate, feed and breed in the currents.

Wandering Albatross (<em>Diomedea exulans</em>). Photo: Tony Palliser
Wandering Albatross (Diomedea exulans). Photo: Tony Palliser
Wandering Albatross (Diomedea exulans) is one of 21 albatross species all identified as globally threatened (compared to just three in 1996). Around 100,000 Wandering Albatross are drowned each year after being caught accidentally on baited hooks set by longline fisheries.© Tony Palliser

Because such creatures are being snared on the 1.4bn longline fishermen's hooks dropped each year scientists want to identify these key meeting places and marine highways. Satellite tags on tuna, elephant seals and sharks are beginning to provide three-dimensional roadmaps of the oceans, which cover 70 per cent of the globe.

Marine highway

"On land, if you want to drive somewhere for vacation, you can pull out the map, find the highway to get you there and the natural landmarks along the way," Larry Crowder of Duke University told the American Association for the Advancement of Science yesterday in Seattle.

"But in the ocean, the roads and attractions don't always sit still. It's not just the animals, but the environment itself that moves."

Sea turtle - an endangered species© Rafel Al Ma ary/Still Pictures
Sea turtle - an endangered species© Rafel Al Ma ary/Still Pictures
Sea turtle is endangered as a result of long-line fishing and pollution.© Rafel Al Ma'ary/Still Pictures

He warned that urgent action was needed. Leatherback and loggerhead turtles had survived 100m years of climate change and asteroid impacts, but "they may disappear within the lifetime of people in this room if we don't change the rules out there somehow", he said.

"The facts are that fewer than 1,500 females nest annually throughout the Pacific, for both loggerheads and leatherbacks. Both species have a 50 per cent chance of extinction in less than two turtle generations."

Loggerheads could vanish in 70 years, leatherbacks in 10.

Dr Crowder said that the cartoon film Finding Nemo provided quite a good characterisation of the marine highway.

"Unfortunately these highways are also locations where there is intensive fishing."

Turtle threat

Longline fishermen hunting for swordfish put out 3.8m hooks a night on lines often 40 miles long, accidentally killing thousands of loggerheads and leatherbacks each year worldwide. The Pacific, where both species are especially endangered, the annual chance of being taken by a hook was 40-60 per cent, he said.

The big predators were slow growing and slow to reproduce, his colleague Andy Read said. Although they travel vast distances and dive to great depths, the species are being fitted with tags to be recorded by satellite, or followed by underwater listening devices, for scientists to track the creatures, map their favourite routes and begin to understand the three-dimensional traffic of the sea.

"The ocean is anything but homogeneous," Elliott Norse of the Marine Conservation Biology Institute said.

Wandering albatross, pelagic sharks, turtles and tuna tended to home in on ocean fronts and gyres where waters collide.

Some bluefin tuna crossed the Atlantic, while albatross circumnavigate the Antarctic. "And they commute among these places, feeding and moving almost as if they were highways in the sea."

Tim Radford is Science Editor for The Guardian.logoGuardian Unlimited © Guardian Newspapers Limited 2004 . This article was first published in The Guardian, (Saturday, February 14 2004). All rights reserved. Reproduced with kind permission.