Gray whale deaths declared 'unusual mortality event'

After 148 gray whales have died along the West Coast from Mexico to Alaska, the National Oceanic and Atmospheric Administration declared the situation an 'unusual mortality event.'

An unusual mortality event is defined as a stranding that is unexpected, involves a significant die-off of any marine mammal population and demands immediate response.

The Eastern North Pacific gray whale population is estimated at 27,000. The last unusual mortality event resulted in about 6,000 whales dying in 1999 and 2000, but the population rebounded.

"We know that it can recover, that's given that all other parameters remain the same - the environment remains essentially the same, there's enough food and other things of that nature," said Dave Weller, a research wildlife biologist at NOAA's Southwest Fisheries Science Center. "I would say that the number one priority is learning as much as we can about the stranded animals."

Although 148 whales have been found stranded, including five in Alaska, the number of whales dead is likely far higher.

"We do know that most whales and especially emaciated whales tend to sink when dead, so the numbers that wash up do represent a fraction of the true number," John Calambokidis, a research biologist with Cascadia Research Collective. "But it's a number that has been difficult to quantify, but certainly it's the vast majority that go unreported, either sinking or in the cases of areas like Alaska, you have remote areas even if they wash up that would make them hard to quantify."

Researchers says the dead whales have been both male and female, adult and juvenile. Most have been emaciated, but the root cause or causes of the problem could takes months to more than a year to determine.

Most of the documented strandings do not occur until weeks after an animal dies. Either the whales float around, or they sink until they bloat and come ashore. When animals decompose before researchers are able to perform necropsies, the information they can learn from the dead animals is restricted.

"We're looking at something in the environment, or perhaps disease. And disease would be a very difficult thing to really detect because of the condition of the whales that they present themselves in," Sue Moore, a biological oceanographer with the University of Washington, said. "And then there's also human-caused mortality of a ship strike or even contaminants in the water. All of these things may be playing a role."

The gray whales' migration suggests that Alaska is just at the beginning of the dead whales that could wash up.

"We are on the early side of things," said Kate Saveage, stranding health specialists with NOAA Alaska Region. "Typically Gulf of Alaska, June we see the most strandings. And then the Bering Sea it's July and August, and then the Arctic is stretches into September. So July, August and September are the peak months, so we're just starting here and we'll see what happens."

NOAA says the most important thing someone can do is to immediately report a dead, injured or stranded marine mammal. The Alaska Marine Mammal Stranding Network can be reached at 1-877-925-7773.