Conundrum

At the same time hundreds of dead gray whales were washing up on beaches, their birthrate was plunging. Theories abound, but little hard data has been gathered to solve this environmental puzzle.

Brownell and Weller think that some sort of "large-scale ocean basin" climatic event has affected both sides of the North Pacific Ocean. They believe the shift took place in the late 1990s and changed the availability of food for both the Eastern and Western Pacific grays in the same way.

Brownell and Weller have no idea what that major environmental change might be or whether an end to industrial development, including oil drilling, or further cutbacks in aboriginal harvesting will, in fact, save the whales -- on either side of the ocean.

But it's important for scientists to figure out whether whales face a problem with abundance or the threat of scarcity. Marine mammal experts, especially the quasi-governmental IWC, will need the science to put in place species management plans. If there are too many whales (the carrying capacity theory), the IWC could decide to allow an increase in aboriginal quotas, for instance. If it looks like the food supply is being threatened by a larger environmental circumstance, officials may be forced to make tough political choices like limiting industrial development in whale territory.

Migrating whales captured by aerial photography.
Wayne Perryman
Migrating whales captured by aerial photography.


Scientists agree there's only one way to solve the dilemma: study what's going on in the Bering Sea.

"What I think is most important for the gray whale now is to actually study the amphipods," says Le Boeuf. "You're probably saving the whales along with it."

Enter Ray Highsmith, who in studying the amphipods may well resolve the essential conundrum over carrying capacity versus environmental collapse.

The University of Alaska-Fairbanks biologist plans to lead a team of researchers into the northern latitudes of the Bering Sea next June and actually measure the amphipods that have been the subject of so much scientific hand-wringing.

Highsmith will be repeating work he did about 10 years ago, a research project that was also funded by the National Science Foundation, not NMFS. As an aside, Highsmith points out that he doesn't even apply for grants through NMFS because the agency never has the kind of money needed for arctic seafaring expeditions, which run into the hundreds of thousands of dollars.

In the previous study, Highsmith identified the gray whales' primary feeding ground as a 47,000-square-kilometer patch of ocean between St. Lawrence Island and the Bering Strait. As many as 3,500 whales were feeding in the area. He believes there is a similar "hot spot" north of the Bering Strait, in Russian waters near Siberia.

In the study area, the large amphipods favored by gray whales were plentiful, about 5,000 per square meter, his study showed.

Those amphipods are about the size of cocktail shrimp and live in the upper few centimeters of the muck on the bottom of the ocean. A feeding gray whale dredges a trench a few meters deep in the upper layer of the bottom, sifting the sand and amphipods through its baleen.

But the same area also contains many smaller types of amphipods, animals that are just too tiny to be trapped by the baleen. It's these smaller creatures that will be key to determining whether the whales are simply overgrazing, as Le Boeuf and his group contend, or whether a more widespread sea change is at work, as Brownell and Weller propose.

Ten years ago, based on the feeding rate of the whales and the reproductive rate of the amphipods, Highsmith predicted that by about the year 2000, the whales would be having a hard time finding enough food. "Lo and behold, about 1999, whales started washing up on the beaches," he says. "The arrows are all starting to point toward the amphipods."

Highsmith applied for the NSF grant about 18 months ago but only got final approval in September. It was too late to do any field work this year; all the research vessels were booked and the weather in the Bering Sea would soon be too rough for bottom-sampling. Now, Highsmith plans to head north in June for 10 days on site, then return next September for a second round of sampling.

Highsmith will repeat the work in as near the same way as he collected samples and analyzed data 10 years ago. That means dropping anchor in the same few spots the team visited before, and using a shipboard system that sends a heavy metal grab bucket over the side. The machine will bring back large samples of the bottom and whatever amphipods might be included. The team also hopes to make use of small, two-person research subs to study the bottom.

And here is where the gray whales' future lies: If only the amphipod species eaten by the gray whales has declined, then scientists can be reasonably certain that the problem is the whales themselves -- the overgrazing or carrying capacity theory. But if all species of amphipods have declined, including those too small to be consumed by whales, then, Highsmith says, it means the amphipods' own food system -- microscopic diatoms that live in the water column -- is in trouble. And that would suggest some larger cause, such as broader climatic change.

Either way, a downturn in amphipods does not bode well for the gray whales. It takes many years for amphipods to reproduce. "If their population is way down, it may not recover for decades," Highsmith says. "In terms of the whales, that's a problem for them."

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