WASHINGTON – Andy Wills was sleeping on a friend's couch in Cordova, Alaska, on March 24, 1989, ready to head out and harvest spring herring in Prince William Sound.

"My buddy had just handed me a cup of coffee in the morning," Wills said. "And there's the Exxon Valdez on TV, spilling oil."

"We were like, 'No!' It was just the start of a nightmare," Wills said.

The herring of Prince William Sound still have not recovered. Neither have killer whales, and legal issues remain unresolved a quarter of a century later. Monday is the 25th anniversary of the disaster, in which the tanker Exxon Valdez ran aground on Bligh Reef and spilled at least 11 million gallons of oil into the pristine waters of the sound.

Prince William Sound today looks spectacular, a stunning landscape of mountainous fjords, blue-green waters and forested islands. Pick up a stone on a rocky beach, maybe dig a little, though, and it is possible to still find pockets of oil.

Presence of oil a surprise

"The big surprise for all of us who have worked on this thing for the last 25 years has been the continued presence of relatively fresh oil," said Gary Shigenaka, a marine biologist for the National Oceanic and Atmospheric Administration.

The question of how well Prince William Sound has recovered from what at the time was the nation's largest oil spill is a contentious one. Exxon Mobil Corp. cites studies showing a rebound.

"The sound is thriving environmentally and we've had a very solid, complete recovery," said Richard Keil, a media relations adviser at Exxon Mobil.

Government scientists have a different view.

The Exxon Valdez Oil Spill Trustee Council, a state-federal group set up to oversee restoration of Prince William Sound, considers the pink and sockeye salmon to be recovered, as well as the bald eagles and harbor seals. Several other species are listed as recovering but not recovered.

Sea otters have had a rough time. Thousands died in the months following the spill, and the population has struggled to recover. The U.S. Geological Survey reported earlier this month that the sea otters of the area had finally returned to their pre-spill numbers.

Listed as still not recovering are the herring, a group of killer whales and the pigeon guillemots, a North Pacific seabird.

Rick Steiner, an ocean activist, said the "spill is not over. The damage persists in quite remarkable ways."

Wills, who fished salmon as well as herring, said the spill left a huge mark on those who made a living from Prince William Sound. Exxon compensation checks were too late and too little, he said.

"A lot of people got real hurt. I know a lot of guys committed suicide and all that stuff. I got divorced, had an ulcer. It was rough," said Wills, who now runs a bookshop and cafe in Homer, Alaska.

Fate of herring a mystery

Among the scientific puzzles of the spill, the fate of the herring is a particular mystery. It's a vital species for the ecosystem, giving protein to whales, salmon and birds.

Prince William Sound was home to a lucrative spring herring fishery that supported fishermen badly in need of cash coming off the long winter in between fishing seasons.

Researchers found lesions and larval abnormalities in herring exposed to the oil. Then, four years after the spill, the herring population crashed dramatically. The reasons are a subject of intense debate, with suggestions that the effects of the spill could have made the herring vulnerable to disease.

"No other stock in Alaska crashed in 1993, so that's indirect evidence it is spill-related," said Jeep Rice, who studied the spill for more than two decades as a federal scientist. "That's kind of weak, and yet it is about as good as we can get in terms of explaining why it happened in that year."

The herring never really recovered, and the current population is too low to overcome predators. Herring fishing, with a brief exception, has been closed for 20 years.

The federal and state governments are still weighing the science of the spill's effects and deciding whether to seek more money from Exxon Mobil for cleaning up remaining oil.

If there is evidence the spill is causing unexpected, continuing damage, the company could be forced to pay up to $100 million on top of the $900 million civil settlement that Exxon paid in 1991. The case lives on in the courts, where the federal and state governments have said more studies are needed.