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ENVIRONMENT-ARGENTINA: When One Ocean Is Not Enough

Marcela Valente* - Tierramérica

BUENOS AIRES, Feb 22 2007 (IPS) - Thanks to satellite tracking, a team of Argentine scientists found that southern elephant seals need much more ocean space to survive than previously thought. They can dive to a depth of 1,200 meters in search of food in the southwest Atlantic, and cross the Strait of Magellan to the Pacific.

The mapping of the movements of the Mirounga leonina, which goes far beyond the Patagonian Sea, is being done in the context of the Sea and Sky Project, a joint initiative of the Wildlife Conservation Society and Argentina’s National Patagonian Centre.

The results “alert us to the fact that to conserve ocean biodiversity the small protected areas are not enough, that greater dimensions are needed, in accordance with the space of the species to be protected,” the project’s executive director, Claudio Campagna, told Tierramérica.

“An integrated model allows us to understand the ecosystem as a whole, incorporating into the management equation the cost of the impacts, in order to assure ourselves that the natural capital isn’t being compromised,” he said.

The Patagonian Sea, which covers two million square kilometres in the southwest Atlantic, is one of the planet’s richest and most productive temperate marine ecosystems, according to the experts at the Sea and Sky Project, who promote a management system based on the precautionary principle.

The waters off the east coast of Patagonia, in southern Argentina, hold high concentrations of phyto- and zooplankton, the sustenance of a wide array of squid, crustaceans and molluscs. And feeding on those species are many types of birds and sea mammals that reproduce along the shore.


That natural food chain is threatened by over fishing. “The idea is to find a balance between the necessities of biodiversity and those of humans. We hope to determine where the sea can be used without worry, and where its use causes an environmental impact that should be stopped,” Campagna explained.

In this context, the elephant seal is a good indicator of whether the environment is viable.

Biologist Valeria Falabella receives satellite data about the location of the animals from when they leave the Valdés Peninsula, on the coast of Chubut province, home to the National Patagonian Centre. A reproductive colony of the elephant seals is found on the coast.

The data is entered into a computer programme that depicts the path followed by the individual seal wearing a transmitter. The programme shows where the elephant seal spends its time, where it stops to feed, providing a comprehensive map of the species’ movement.

“Determining areas of relevance for the survival of the species is fundamental for progress in conservation efforts, and these tools help us understand the biological requirements of the species and how human activities interfere,” Falabella told Tierramérica.

Since the project began in 2003, 23 elephant seals have been studied using satellite data. Currently, 11 are being tracked.

Elephant seals are born weighing about 40 kilograms and are weaned at just three weeks, when they weigh 130 kg, gained solely from mother’s milk. Adult females weigh 600 kg on average, while males are much larger, reaching 3,000 kg. “Adults live to just 14 or 15 years,” said Campagna.

Tracking the elephant seals has revealed that the adult males feed mostly along the continental platform and slope – a band extending about 300 kilometres from the coast, where there are important fisheries. The movements of females, meanwhile, extend up to 1,000 km from shore.

Two of the females that were tracked from the Valdés Peninsula reached the Pacific, and one returned 228 days later, through the Strait of Magellan. In her journey of more than 1,800 km, she gained 179 to 196 kg, indicating a long but successful trip.

Another female reached South Georgia Island, at the south-eastern limit of the Patagonian Sea, and there are data from other seals that reached the Antarctic Peninsula. In their travels, the elephant seals dive as deep as 1,200 meters, returning to the surface every half hour to breathe.

Each time they emerge, the satellite transmitters they wear on their head emits a locator signal.

Mirtha Lewis, a veterinarian and co-director of the elephant seal project at the National Patagonian Centre, told Tierramérica that every October about 14,000 pups are born on the Valdés Peninsula, where the total population is estimated at 42,000.

“But that total is not simultaneously found on the coast,” she explained.

“The elephant seals alternate feeding periods at sea with periods of several weeks on land when they don’t eat,” said Lewis. The maximum observed along a 200-km stretch of coastline there is 25,000, she added.

“In contrast, when the elephant seals are feeding at sea, the area of distribution is much broader, covering about 4.7 million square km in the southwest Atlantic, but some cross to the Pacific and others reach the Georgia Islands,” said the expert.

(*Originally published by Latin American newspapers that are part of the Tierramérica network. Tierramérica is a specialised news service produced by IPS with the backing of the United Nations Development Programme and the United Nations Environment Programme.)

 
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