Gray Whale Chow Line—Closed?
INTRO: Each summer, the frigid Bering Sea and Arctic Ocean off Alaska plays host to thousands of hungry gray whales. The whales come from the warmer waters of Southern California and Mexico to feed on the seafloor's rich abundance of tiny crustaceans. But over the last few years, hundreds of emaciated gray whales have washed up along the U.S. and Canadian west coast. Scientists think the whales might not be getting enough to eat, so this week a team of University of Alaska Fairbanks researchers are in the northern Bering Sea, following a hunch that these once-rich waters may not be so rich anymore. Doug Schneider has more in this week's Arctic Science Journeys Radio
STORY: Twenty years ago, when marine scientist Ray Highsmith last came to the northern Bering Sea,to the waters that separate Alaska and Russia, the ocean bottom was quite literally blanketed by colonies of tiny crustaceans called Ampelisca macrocephala. And feeding on these minute creatures were thousands of gray whales, some weighing more than 40 tons.
HIGHSMITH: "Gray whales migrate all the way from southern California and the Baja California region up into the Bering Sea, and some go even farther north yet to the Bering Strait. But quite a number, a few thousand, feed between Saint Lawrence Island and the Bering Strait. They feed on a small crustacean called an amphipod. These live in rather flimsy tubes that they make in the sand down to a depth of about ten centimeters maximum. The gray whales go to the bottom in these areas and roll to the side. Using their tongue, they create a suction and slurp out sand and everything and then blow the sand and water out the other side of their mouth, while catching the amphipods on their baleen. It's a rather unique feeding method."
Highsmith is a research professor at the University of Alaska Fairbanks School of Fisheries and Ocean Sciences, and director of the West Coast and Polar Regions Undersea Research Center. He says that in the 1980s, amphipods were abundant over a huge swath of the northern Bering Sea. Gray whales numbered around 20,000 then, but were increasing at a rate of about 600 whales each year. Highsmith figured that sooner or later, there wouldn't be enough amphipods to go around.
HIGHSMITH: "So when we were there before, the density of amphipods of the particular type they specialize on was just under 5,000 per square meter. And the entire feeding area we estimated was about 43,000 square kilometers. So it's a tremendous food patch. We were able to estimate the productivity of these amphipods, and it's one of the highest production rates recorded anywhere in the world for marine organisms. We also predicted, based on the data, that the whales were at some risk of exhausting their food supply by 2002."
Now scientists want to know if that's indeed what happened. In the last four years, gray whale numbers have dropped significantly, from around 26,000 to just 17,000. Hundreds of dead gray whales have washed up onto beaches from Alaska to Baja.
HIGHSMITH: "Now that there's been a major count of the entire population, I think there's reason for concern."
To get a better fix on whether the decline was triggered by a shortage of food, or something else, Highsmith and others are aboard the University of Alaska research ship, Alpha Helix. They're conducting a ten-day intensive survey of the seafloor. They'll re-survey the places they looked at in the 1980s, to see what might be happening to the gray whale's favorite food.
HIGHSMITH: "A population that goes from 26,600 to around 17,500, well, that's a huge difference. So it makes our study more critical right now because if food is the answer, there may not be much we can do about it. But if the food supply is down, if these amphipods are not nearly as abundant, then we can work on why. Is it overfeeding by whales? Is it climate change or El Niño? Is it some shift in the productivity of the Bering Sea? Then we can start to work on that. Or are there some other things going on among the whales? It looks like the whales turn up in a weakened state and are more susceptible to some of these other problems. But why do they get weak in the first place?"
OUTRO: We'll check in with the researchers when they return from their ocean cruise to see what they found. This is Arctic Science Journeys Radio, a production of the Alaska Sea Grant Program and the University of Alaska Fairbanks. I'm Doug Schneider.
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Thanks to the following individual for help preparing this script:
Ray Highsmith, Director
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