ENVIRONMENT
02/28/2014 06:44 pm ET Updated May 01, 2014

Sea Otters In Prince William Sound Back to Pre-Exxon Valdez Oil Spill Numbers

A couple of sea otters sits on a float in the Cordova, Alaska boat harbor Thursday Feb. 7,  2008. The Exxon Valdez oil spill
A couple of sea otters sits on a float in the Cordova, Alaska boat harbor Thursday Feb. 7, 2008. The Exxon Valdez oil spill soiled 1,200 miles of shoreline and killed hundreds of thousands of birds and other marine animals. The Supreme Court is scheduled to hear arguments on Feb. 27, 2008 from Exxon about why the company should not have to pay the $2.5 billion punitive damages awarded to victims of the disaster that happened 19 years ago when the Exxon Valdez ran aground on Alaska's Bligh Reef, spurting 11 million gallons of crude oil into the rich fishing waters of Prince William Sound. (AP Photo/Al Grillo)

OLYMPIA, Wash., Feb 28 (Reuters) - Nearly 25 years after the Exxon Valdez oil spill off the southern coast of Alaska, sea otters in the most affected parts of Prince William Sound have recovered to their pre-spill numbers, a federal report released on Friday showed.

Several thousand sea otters died in the aftermath of the oil tanker running aground on Bligh Reef and leaking 42 million liters of crude oil into the sound in March 1989, according to the U.S. Geological Survey, which issued the report.

The report's findings underscore the lengthy recovery times for many species affected by oil spills, U.S. Geological Survey research biologist Brenda Ballachey said in a statement.

"Although recovery timelines varied widely among species, our work shows that recovery of species vulnerable to long-term effects of oil spills can take decades," said Ballachey, the study's lead author.

Scientists assessed the otters' recovery by using aerial surveys, measuring oil exposure as indicated through gene expression and by evaluating the animals after death.

After the spill, middle-aged otters died at a higher-than-normal rate - a trend that has since reverted to the pre-spill pattern of most otters dying either very old or very young, the study found.

The slow pace of recovery for the otters was likely due to their ongoing exposure to oil, the study found.

Sea otters were among more than 20 near-shore animal species damaged by the spill, the U.S. Geological Survey said. (Reporting by Jonathan Kaminsky; Editing by Dan Whitcomb and Ken Wills)

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