Dolphin Researchers Focus on Alboran Sea

Bijal P. Trivedi
National Geographic Today

February 28, 2003

The research vessel, a century-old 60-foot gaff-rigged ketch, looks more like it belongs to Barbary pirates than to contemporary scientists.

But Ana Canadas and Ricardo Sagarminaga, a Spanish husband-and-wife team of marine biologists, refitted the Norwegian fishing vessel Toftevaag to study dolphins, porpoises and whales in the Alboran Sea, the western portion of the Mediterranean between Spain and Morocco.

The Alboran plays a crucial role for dolphin and man. Every year, 20 percent of the world's maritime traffic passes through the Alboran—which also happens to be what the researchers call "a regeneration zone" for Mediterranean marine life.

Canadas and Sagarminaga, based at the University of Madrid, want to know how the cetaceans are faring in this heavily trafficked but biodiversity-rich region of the Mediterranean.

"The distribution of dolphin populations in the Mediterranean is really a reflection of the state of the health of the Mediterranean Sea," said Sagarminaga, conservation program coordinator for the Spanish Cetacean Society and skipper of the Toftevaag.

In the Alboran, bottlenose dolphins travel in pods of about 33 creatures, but which sometimes swell to more than 100, Sagarminaga says. However, in the eastern Mediterranean, east of Sicily, pods average only about eight dolphins.

Sagarminaga and Canadas, a doctoral candidate, hope that their research will help persuade the Spanish government to create a so-called Marine Protected Area in the northern Alboran.

Investigating a Massive Dolphin Die-Off

Such a designation would regulate commercial traffic, fishing and tourism. Also, an MPA, Canadas expects, would help the flourishing marine mammal populations "spill over and repopulate eastern regions of the (Mediterranean) sea."

Canadas and Sagarminaga have been collecting data in the Alboran since 1990—in effect, taking a dolphin census. The couple and many other marine biologists believe that cetacean numbers have fallen in the last decade, but the problem has been proving their hunch. There is a tremendous lack of historical data.

"Whether the populations have definitely declined or just redistributed is difficult to determine," said Philip Hammond, a marine mammal population ecologist at the University of St. Andrews in Fife, Scotland, who is one of Canadas' doctoral advisers. "If anyone's data will help answer this question, it will probably be Ana's."

About four years ago Canadas realized the value of her data and wanted to subject it to more thorough analysis; In about 2000 that she began her PhD work.

"Over the last decade Ana has collected the most extensive data set—in terms of duration and areas covered—on cetaceans in the Mediterranean," said Hammond. "They [Ana and Ric] have done this project very cheaply, on a shoestring, and they have still come up with the best data."

In 1990 Canadas and Sagarminaga came to the Mediterranean to study a sea turtle nesting ground in Tunisia. Later that year they turned to investigating a massive dolphin die-off that stretched from Spain to Greece.

To help sustain their research, the couple founded Alnitak, a non-profit University of Madrid-linked environmental organization. Earthwatch has funded Alnitak since 1999.

A Noisy Underwater World

The Mediterranean has suffered heavily from overfishing and the effects of pollution—hydrocarbons, heavy metals, debris, sewage from tourist sites and noise from maritime traffic.

Although the dolphin population in the Alboran seems healthy, the creatures may face a new threat from the fisheries. The industry is stepping up the sardine catch to feed farm-raised tuna.

"We don't know whether this is a problem for the dolphins or whether their spectrum of prey is broad enough to compensate," Canadas said.

In 1997 Canadas and Sagarminaga expanded into bioacoustics, using a hydrophone—an underwater microphone—to study dolphin communication.

The couple launched genetic studies in 1999, collecting tissue samples from stranded animals or those caught up in fishermen's nets.

Today, aboard the Toftevaag, with a crew of four researchers and up to eight volunteers, Canadas and Sagarminaga are taking a hands-on approach.

When curious dolphins swim around the boat, the team launches an inflatable boat. The researchers reach out to the dolphins with a sponge-tipped pole and try to swab them. The flakes of skin on the sponge go into a tube for DNA analysis.

The Toftevaag also eavesdrops on the dolphins. Manolo Castellote, a visiting bioacoustics researcher, sits with headphones on, staring at a computer screen showing digital imaging of dolphin clicks—"sort of k-k-k-k-k-k, rhythmic sounds," he said.

But manmade sounds drown out the dolphins—"this kind of beep-be-deep, beep-be-deep, that's VHF interference made by ships," said Castellote. "The Mediterranean is a very acoustically polluted sea."

"All these species use the same frequencies of sound as the engines of big ships," Castellote said. The engine sounds may somehow interfere with the dolphins' communication or possibly deafen the animals with high background noise.

The Alboran may be noisy and chaotic but the dolphins thrive there. Canadas and Sagarminaga want that vitality to continue—and to extend ever easterly.

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