Whale deaths a mystery

US authorities are investigating the mysterious deaths of eight whales found washed ashore along the Sea of Cortéz in January, an unusually large number that suggests someone or something is killing them off.

The whales come from several plankton-eating species and apparently died at sea in November and December, biologists said. But they do not show signs of having been caught in long-line fishing nets, which sometimes suffocate them. Nor have biologists found any signs of a toxic spill or outbreak of disease that would account for their deaths.

The first sign something was wrong came on January 4, when the remains of
two humpback whales were spotted on the shore near the town of El Dorado in Sinaloa. Scientists determined they had died in early November. Since then, six more giant bodies have turned up, among them a third humpback, a minke whale, a fin whale and a baby gray whale. Three bodies were discovered on January 18 during an aerial search of the Sinaloa coast.The discovery of the carcasses set in motion a frantic search for forensic evidence. Biologists tracked currents to determine if all the whales might have been in the same place when they died, even though they ended up scattered over a 500-mile coastline. The investigators also looked for signs of disease or poisons, both natural and synthetic. It was slow going. All of the bodies were badly decomposed. Only the baby gray whale provided enough tissue to test for diseases or poisons.

On Friday February 17, environmental officials announced that those tests had found no evidence of a toxic algae bloom, other poisons or infections. Nor have the investigations turned up signs of mistreatment by fishermen. The deaths occurred just as about 2,000 gray whales began arriving in the Sea of Cortés, where they spend winter every year as part of a centuries-old
migration. Officials say they usually find about 10 dead whales a year; nine in two weeks have set off alarm bells. Environmentalists say the Sea of Cortés, one of the world´s richest fisheries and most diverse marine habitats, is poorly policed and overfished, because the Mexican government has granted more and more permits for trawlers to use long-line nets. The deaths of so many whales has prompted urgent calls from environmental groups for quick action to find the cause.

Besides the whales, two dolphins and an olive ridley sea turtle have also washed up dead in the same region. None of the bodies showed signs of wounds from nets on their fins, nor signs of other trauma that might have been caused by fishing boats. Biologists also did not find the usual telltale massacres of fish and sea birds that would accompany a toxic bloom of algae or another release of poisonous materials.

source: El Universal