Deaths May Signal Too Many Whales for the Ocean

A record number of gray whales has washed up dead on West Coast beaches this year, and the number of calves migrating this season is the lowest ever recorded, leading scientists to believe that the once-endangered mammals may have rebounded past the Pacific Ocean’s capacity to nurture them.

If the gray whale population is indeed nearing carrying capacity along the Pacific Coast, it would mark the first time a whale species nearly wiped out by a century of hunting had recovered to its maximum potential--the largest number that the ocean can support.

Scientists cautioned that unusual ocean temperatures, a late breeding migration and food supply problems in the Arctic feeding grounds also could be affecting the whale population. But, they said, the 26,000 whales now plying the Pacific Coast are very close to what is believed to be the maximum populations that existed before the advent of commercial whaling in the 19th century.

“What we’re seeing is not inconsistent with the idea that gray whales may be nearing what the environment can handle,” said Wayne Perryman of the National Marine Fisheries Service, which has counted calf production off the California coast since 1994. “What naturally limits populations generally is either space or food, and I’d guess that’s what we’re starting to see now.”

‘Amazing Grace’ for a Dead Whale

The emaciated carcass of a 2-year-old, 27-foot female that washed up on a suburban Seattle beach last weekend was the most visible of the whale deaths, drawing flocks of onlookers and an impromptu rendition of “Amazing Grace” to mourn her passing.

Five more whales have washed up on Washington beaches since then, bringing this year’s total to a record 17, well above the average over the last 20 years. Higher-than-normal death rates have been recorded along the coasts of Oregon, California and Mexico as well.

Whale deaths in California over the last two years have been double the average in the last 15 years, said Joe Cordero of the National Marine Fisheries Service in Long Beach. And because most whale deaths occur in June, at the end of the whales’ 4,000-mile migration between Baja California and Alaska, that number is expected to rise.

As many as 65 whales have died off the coast of Mexico this year, biologists said.

Most of the dead whales this year were extremely thin, leading researchers to believe that they either starved or succumbed to other problems because of their poor condition. And while most of them were juveniles--the group that typically washes ashore when there are deaths during the migration--biologists for the first time this year documented a number of nearly full-grown, 40-foot-long whales, said Joe Scordino, a biologist for the federal fisheries service in Seattle.

No one is ready to say what is definitely causing the higher number of deaths, especially since there is only a year’s worth of data. It may simply be that there are more deaths because there are more whales, Scordino said.

“I think it’s safe to say that the population size is up, so you’d expect to see more mortalities. . . I think it’s too soon to say that there’s something going on in the environment that’s affecting their food availability,” he said.

The rising number of whale deaths coincides with a sharp drop in calf production.

“We’ve counted about 135 northbound calves, and, sort of what I think is a normal year at this time, we’d probably see closer to 400 now,” Perryman said.

Unusually warm ocean temperatures, he explained, could have affected calf production. The southerly migration got underway later than usual, the whales spent less time than normal in their Baja California breeding lagoons and were documented in areas of Mexico where they hadn’t been seen before. “So maybe not as many females got pregnant last year,” Perryman said. “But if I were going to make a guess right now, I’d say it has something to do with nutrition.”

Gray whales, once they reach whatever the Pacific’s carrying capacity is, could be expected to die off and to lower their reproductive rates because normal food supplies can sustain only a certain population.

“It’s generally thought that carrying capacity is somewhere in the neighborhood of 25,000 to 30,000,” said John Calambokidas, research biologist for the Cascadia Research Collective in Olympia, Wash.

Although some gray whales in recent years have fallen victim to ship strikes and killer whale attacks, the fact that so many appear to be nutritionally deficient could be evidence that the population is nearing carrying capacity, Calambokidas said.

The maximum capacity theory may fuel arguments in favor of whaling by the Makah Indian nation, a northwest Washington tribe that has won permission for an aboriginal hunt of five gray whales a year over the next five years. The tribe landed its first whale last month amid vigorous protests and death threats.

Paul Watson, head of the Venice, Calif.-based Sea Shepherd Society, which opposed the Makah hunt, said the whale deaths more likely are due to environmental toxins, such as metal traces and chemicals from agricultural runoff, than food deficiencies.

“Gray whales have the highest concentration of heavy metals of any whale in the ocean, and they’re coming along the California coast, which contains probably the most toxic runoff of agriculture anywhere in the world,” Watson said.

Scordino said the whales that washed up dead this year have been tested for DDT and PCBs, and have shown no elevated levels. But heavy metal testing is too expensive for the fisheries service to do, he said.

In the past, Scordino added, gray whales have shown relatively high levels of metals like aluminum. But that could be due simply to the fact that they are bottom feeders and scoop up so much sand when they eat. “Aluminum silicate is a big component of sand, so it’s probably normal background for gray whales to have aluminum.”

Moreover, concerns about agricultural runoff would not explain this year’s higher-than-normal deaths, Calambokidas said, since there is no reason to believe runoff levels are elevated this year. “It would also be unusual because animals are generally not feeding much in California.”

Normally, gray whales fast during the months of the migration, bulking up again in the Bering Sea between Alaska and Siberia before the following year’s migration. Occasionally, they are known to snack along the way. But scientists are documenting an unusual number of instances of gray whales straying into inland bays in California, Oregon and Washington, and in some cases those whales are remaining throughout the year, failing to return to Alaska to feed.

It is not known if this is something truly new of if some whales always have done this and scientists are seeing it because they are only beginning to look for it. “If the trend changes to more whales sticking around,” Scordino said, “then that’s going to be a big question.”