ANCHORAGE - 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.