One pod of whales recovers after the Exxon Valdez oil spill, other near extinction

Two groups of orca whales that frequent Prince William Sound each lost about 40 percent of their populations to the Exxon Valdez oil spill.

Today, one tight-knit group that form a pod appears on a slow road to recovery.

The other — more dispersed — group appears doomed, and hasn't had a new recruit since 1984, said Craig Matkin, a marine-mammal biologist who has studied the whales for 26 years.

It is unclear why the fates of the two groups diverged so dramatically. But the populations have different cultures and don't mingle, according to Jeep Rice, a federal biologist with NOAA Fisheries.

The recovering pod is sustained largely by fish. It had about 36 whales at the time of the spill, and declined to fewer than 20. The numbers have rebounded to about 28.

The group in sharp decline feeds largely on marine mammals, including the harbor seal that also has been in decline. This group was smaller — but relatively stable — at the time of the spill, with about 22 whales in the group, according to Matkin.

The early toxic effects of the spill appeared to kill two females of breeding age, and the group's numbers today are down to seven. The group includes two females, but they are aging and haven't had offspring in years.

"They are headed for extinction unless some miracle happens," Matkin said.

Hal Bernton: 206-464-2581, hbernton@seattletimes.com