Where have all the dolphins gone?

The alarming drop in numbers of the Bay's three most common species of dolphin -- the striped, bottlenose and common -- can be attributed to one or both of two causes, Clive Martin, senior wildlife officer for the Biscay Dolphin Research Programme, told AFP.

"We know for a fact that by-catch is killing thousands of dolphins every year," he said, referring to commercial fishing operations in the bay, which is formed by the northern coast of Spain and the eastern French seaboard up to the tip of Brittany.

Martin singled out French "pair trawlers" that sweep the ocean with huge nets twice the size of a football pitch strung out between them as being especially lethal to the marine mammals.

"Dolphins are sometimes trapped hundreds at a time, and are asphyxiated" when they cannot come up for air, he said. Most dolphins typically replenish their lungs with fresh air every five minutes or so, he explained.

The second -- and probably more important -- reason that dolphins have disappeared is that there is simply very little left for them to eat.

"Anchovy fishing in the Bay of Biscay has progressively failed, and this year there is a complete ban by Spain, France and the United Kingdom on the fishing of anchovies," a principal food source for dolphins, Clive said.

He speculated that the roving sea mammals -- which swim in pods numbering in the dozens for bottlenose dolphins, and sometimes in the thousands for the common dolphin -- had moved west toward the mid-Atlantic looking for food.

A sharp decrease in the presence of many seabirds that also feed on fish -- such as auks, shearwaters and gannets -- lends support to this explanation.

The Bay of Biscay Research Programme has been systematically recording dolphin sightings along the same route from Bilbao, Spain to Portsmouth, England for 13 years.

Compared to the comparable period in 2004 and 2005, dolphin sightings in 2007 have decreased by 50 percent, he said.

The Bay of Biscay hosts a greater variety of dolphin populations than any other part of the world's oceans. Clive suggested that policy makers should consider transforming the area into a sanctuary for marine life.

© 2007 AFP