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Scientists probe death of whales

Something is killing the giant mammals off Nova Scotia -- and toxin suspected


Globe and Mail

5th August 2003

HALIFAX -- Scientists hope to learn this week what has killed at least 17 whales since mid-June off the southwestern coast of Nova Scotia in a shallow area straddling Canadian and U.S. waters.

Marine biologists from both countries believe a common toxic algae called red tide may have been passed on to the whales in the small fish -- mostly mackerel and herring -- they eat.

"It is very uncommon for such a large number to be affected," said Jerry Conway, marine mammal adviser with the Department of Fisheries and Oceans. The last time so many whales died this close together was in 1987 when red tide killed 14 off the New England coast.

Last Tuesday, a U.S. fishery patrol boat discovered four dead whales -- three humpbacks and one finback -- on the northeastern tip of Georges Bank, an underwater plateau that extends from Nova Scotia to Cape Cod, separating the Gulf of Maine and the Atlantic Ocean.

They found several more humpbacks and a pilot whale over the next few days before adding about a dozen more to the toll. Those whales had turned up dead in the previous six weeks in the same area; most were found within 80 kilometres of each other and had been dead between one week and one month.

Scientists from the Woods Hole Oceanographic Institution in Massachusetts took samples by cutting open the carcasses and removing bits of skin, blubber, faeces, urine, liver and intestinal tract.

"It's hard to imagine anything other than a toxin that would kill an animal that quickly," said Donald Anderson, senior scientist at Woods Hole. "It's a highly unusual situation. Fourteen whale deaths in one month are equivalent to 50 years of mortality."

Tissue samples from six whales have been sent to a lab in South Carolina to determine the cause of death. Teri Frady, spokeswoman for the U.S. National Oceanic and Atmospheric Administration Fisheries in the Northeast, the federal agency charged with whale protection, said researchers may have to haul a carcass to shore for another look if tests are inconclusive.

The Canadian Food Inspection Agency is also testing whale samples and area shellfish for the toxin, Mr. Conway said.

Red tide is a naturally occurring part of the food chain. Small quantities seep into a fish's organs, but not the meat. Small quantities will not typically affect humans, but large amounts can cause nausea, fever, paralysis and even death.

The toxin hits whales harder, however, because they eat whole fish by the tonne; the toxin prevents them from breathing or being able to surface properly. If toxins caused the whale deaths, not much can be done for them.

"But I'm not too concerned about [it affecting humans]," Mr. Anderson said. "If the deaths are linked to toxin, the most likely pathway to the whales is via fish. They eat three or four times their body weight a day. Normally fish will die before they reach levels dangerous to humans."

Patrol boats and aircraft continued yesterday to search from Cape Breton to the Bay of Fundy for carcasses. The area is home to as many as 2,000 humpback whales which are an enormous tourist attraction at this time of year.

Primarily inshore animals, the whales prefer these relatively shallow waters, especially when feeding their young, but they are constantly at risk of being hit by ships or getting entangled in fishing gear. None of these carcasses showed any obvious injury.

"What's also strange is that all around the dead whales are very active whales that are unaffected," Mr. Conway said. "It's a big puzzle right now."

Fortunately, he said, the mystery has not claimed any of the endangered right whales; only 320 exist in the North Atlantic, including about 60 breeding females.