Oil companies operating in the Chukchi Sea off Alaska's northwest coast will have a negligible effect on polar bears and walrus, according to a federal Appeals Court ruling Tuesday that backed U.S. Fish and Wildlife Service rules on harassment of the animals.

A three-judge panel of the 9th Circuit Court of Appeals said the agency correctly issued rules that provide legal protection to oil companies if small numbers of polar bears or Pacific walruses are incidentally harmed.

"We're glad that the court has reaffirmed the appropriateness of our conservation measures," agency spokesman Bruce Woods said.

The Center for Biological Diversity sued over the rules, claiming both individual animals and entire populations must be analyzed for protection. Center attorney Rebecca Noblin said the Appeals Court agreed but concluded the Fish and Wildlife Service had done sufficient separate analyses. Noblin called the decision disappointing.

The Marine Mammal Protection Act generally prohibits the "take" of marine mammals. Take is defined to include harassment or annoyance that has the potential to injure or that could disrupt behavior patterns such as migration, nursing, breeding and feeding.