Good news for otters: Officials have said that sea otters in Alaska's Prince William Sound have recovered after a deadly oil spill in recent years.

The Exxon Valdez oil spill disaster of 1989 hurt otter populations and lowered their numbers, but a study has shown that the otters have since recovered to the levels seen prior to the spill, The Associated Press reported.

The crude oil displaced during the spill contributed to sea otter deaths, according to the U.S. Geological Survey study that was released Friday, as reported by the AP.

The supertanker spilled 10.8 million gallons of the stuff after running aground 25 years ago. Shortly after the disaster, the bodies of around 1,000 sea otters were recovered.

The incident serves as a reminder that oil can affect the environment for decades, said research scientist Brenda Ballachey, as reported by the AP.

Later otter deaths were likely connected to the spill since the crude oil persisted in the area for some time, Ballachey said.

"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," Ballachey said in the U.S. Geological Survey report.

"For sea otters, we began to see signs of recovery in the years leading up to 2009, two decades after the spill, and the most recent results from 2011 to 2013 are consistent with recovery as defined by the Exxon Valdez Oil Spill Trustee Council."

Researchers estimated in the study that more than 20 species were affected by the spill. They examined the otter population by evaluating found otter carcasses to see how old the animals were when they died.

After the oil spill, otters of all ages were found dead, instead of the very young or very old, which are normally the most vulnerable, but the population's status has since returned to normal. 

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