An already fragile population of killer whales that hunts Prince William Sound never recovered from the Exxon Valdez oil spill and is doomed to die off, biologists said this week.
Marine mammal biologist Craig Matkin of Homer has tracked the animals since the mid-1980s and said he never thought he'd see an entire population of whales -- even a small one -- disappear.
"To blame it all on the spill would not be fair, but that's the final death blow," Matkin said.
The plight of this group of killer whales contrasts with the full or slow, partial recovery of many other animal populations, including another group of whales, since the 1989 oil disaster.
Twenty years after the massive spill, as much as 16,000 gallons of oil linger in Prince William Sound. Arguments linger over whether Exxon should pay more for cleanup work. And federal scientists and other researchers at an environmental conference in Anchorage this week say they're still learning what the massive spill meant for local wildlife.
Pink salmon fully recovered, they said. The number of sea otters at Knight Island began to climb in recent years after a long stagnation and even decline, though Exxon and government scientists disagree on whether leftover oil could be hurting the animals' ability to rebound.
But a crash in the herring population first detected in 1993 -- and whether the spill played a role -- continues to raise questions and needs more study, scientists said.
One of the most striking surprises to emerge from the annual Alaska Forum on the Environment was the tale of the so-called "AT1" population of killer whales.
Twenty years ago, the population numbered 22 whales. Today, only seven remain.
"These are the unexpected things. In killer whales, not recovering for this long length of time is something that we certainly didn't foresee or predict," said Jeep Rice, senior scientist with the National Marine Fisheries Service's Auke Bay Laboratory in Juneau.
Even before the spill, the AT1 whales were in deep trouble.
They eat harbor seals, which had been in decline for decades by the time of the oil disaster. The whales were also assailed by pollutants and pesticides that might have arrived in Alaska on weather systems from Southeast Asia and might hamper reproduction -- toxins were found in the whales' blubber, Matkin said.
Then the tanker Exxon Valdez ran aground on Bligh Reef in Prince William Sound, and the estimated 11 million gallons it spilled killed thousands of birds and other wildlife.
The whales were known to be in the area. A Los Angeles Times photo shows four AT1 whales swimming near the leaking tanker.
Over the next year, more than a third of the whales died, and the population continued to fall.
The group is more than a pod. It's the remains of a larger genetic population bound by family ties and social bonds, with its own distinct "language" of calls, said Eva Saulitis, a marine biologist who works with Matkin at the nonprofit North Gulf Oceanic Society.
The depleted population won't mate with other groups, Saulitis said. The remaining whales may be too closely related to have calves, and the two remaining females are getting too old to reproduce.
She estimates this group of whales will be extinct within 25 years.
Their distinct dialect of calls, such as the long, loud blast a lone male sounds when he's separated from the group, will die with them.
For other animals, scientists report mixed results.
If you ask Exxon, local animals are all on the road to recovery. The company insists the spill caused no long-term damage to the region. "The exposure to the remaining oil is very small and is decreasing," said Paul Boehm, a chemical oceanographer and petroleum chemist consulting for the oil company in Alaska.
Boehm's job includes gauging how much oil remains in the Sound. He says nearly all that's left is weathered patches of nontoxic oil residue and that the oil is in places or depths where critters like otters don't dig and ducks and their food sources aren't exposed.
The Exxon Valdez Oil Spill Trustees Council disagrees. The council is charged with using the nearly $1 billion Exxon agreed to pay for restoration efforts in a 1991 settlement, and it pays for the continuing killer whale studies in the Sound.
Oil buried in some parts of the Sound is still as toxic today as in 1989, said spokeswoman Rebecca Talbott, and it may be slowing the ability of species such as the harlequin duck to rebound from the spill.
In western Prince William Sound, otter populations have been growing by about 4 percent per year -- about half of the pre-spill growth rate, said USGS research wildlife biologist James Bodkin.
In places like Herring Bay at Knight Island, as many nine out of 10 otters died after the spill, Bodkin said.
In the last year, researchers are seeing the first evidence the population might be rebuilding, but the signs of recovery were a long time coming, possibly because otters encountered leftover oil when digging for clams in intertidal areas over the past 20 years, Bodkin said.
Rice estimates roughly 13,000 to 16,000 gallons of oil remain in the Sound's intertidal zones.
Scientists see no sign the leftover oil is now relevant to the killer whales' survival, but whether the oil is still harming other animals or Prince William Sound in general is a high-stakes question.
It strikes at a still-unresolved 2006 request by the state and federal governments for Exxon to pay another $92 million for restoration projects.
The request is based on a "reopener" clause in Exxon's $900 million civil settlement from 1991.
It said the oil company could be forced to pay up to $100 million more if evidence surfaced that the spill is causing unexpected, lingering damage to the environment or wildlife.
Logan said that request is still being negotiated.
THE SEA WORLD FACTOR
Biologists have wrestled since the spill with deciding how much of the animal-population changes can be pinned on the oil spill, as opposed to other factors. Relatively little research was devoted to many of the animals before the spill.
But the killer whales were different.
Biologists began counting them in the Sound years before the oil spill. Sea World had proposed plucking killer whales for their aquariums, and that triggered substantial research on the whales. Biologists got a detailed record on the small groups that hunted in the region. They took photos of each whale. They could identify each by its markings or even nicks on its fins. Most of all, they knew exactly how many whales hung around Prince William Sound. (Sea World never got its whales.)
Two of the groups were already local celebrities -- swimming near shore or popping up next to anchored boats in the nooks and crannies of Prince William Sound.
The larger of the two was the AB pod, a group of "resident" whales, meaning they feed on fish.
The AB pod numbered 36 whales in 1989, having rebounded from shootings by longline fishermen who didn't like the whales stealing black cod from their lines, Saulitis said.
Six days after the spill, Matkin saw the whales swimming through heavy sheens of oil.
Breathing oil vapor can be lethal, and seven of the whales went missing that first week. Another six disappeared over the following winter, Saulitis said.
Since 1989, the pod has been slow to recover, she said, probably because it lost five reproductive females, plus several juveniles who could have replenished the group.
The pod's official count is now up to 29 whales, but that includes several who split off to join another group -- a move unprecedented among resident killer whales, Saulitis said.
"They're just eking along."
PATH TO EXTINCTION
The other most commonly seen collection of killer whales in the Sound was the AT1 population.
It's a transient group, meaning the whales hunt mammals and are more quiet, stealthy and secretive than their resident cousins, Saulitis said.
The North Gulf Oceanic Society researchers know of another genetically distinct population of transient killer whales that sometimes hunt in the Sound, but they don't visit every year.
And unlike other transient whales that can range thousands of miles, the AT1 group sticks to the relatively small hunting grounds of Prince William Sound and Kenai Fjord.
They've lived there for generations, maybe since the last ice age, Matkin said. "We're talking thousands of years."
The population of 22 whales dropped to 13 over the first winter after the spill. It lost two reproductive females and two juveniles, Saulitis said.
Between 1990 and 1991, another two whales died.
The biologists waited for years to draw a connection between the initial decline in transient killer whales and the oil disaster to make sure the missing whales didn't return or show up somewhere else.
"We were making darn sure that those animals were dead before we brought them into this whole picture," Matkin said.
The biologist, with Saulitis, Rice and others, published a 2008 study that said the spill accelerated the AT1 whales' path to extinction while the larger AB pod hadn't recovered to pre-spill numbers.
Without studies of the bodies of dead whales to declare a concrete cause of death, evidence linking the spill to the initial decline in whales is circumstantial.
A murder mystery without the body, Matkin said.
But the sudden disappearance of 30 to 40 percent of the AB and AT1 whales 20 years ago was either caused by the spill, or it's the biggest coincidence ever, he said.
"There's no doubt they're dead, and there's no doubt they died at the time of the spill."