ANCHORAGE, Alaska (AP) — 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.

A polar bear killed by a security guard at a BP oil field was the only animal known to be killed by industry activity in recent years, Noblin said. The guard hit the bear with a "cracker round" designed to make a loud noise.

The bigger issue, Noblin said, is the effect of oil company noise on two species that rely heavily on sound. Walrus in recent years have congregated on Alaska shoreline shore in the absence of sea ice over shallow feeding areas, she said, and noise could set off a stampede that kills young animals.

"It can impact the animals' behavior, or their hearing itself," she said. The rules, she said, allow harassment of unlimited numbers of polar bears and walrus.

Appeals Court judges concluded that the Fish and Wildlife Service determined that only "relatively small numbers" of polar bear and walrus would be "taken" in relation to the size of their larger populations. The agency determined separately that anticipated take would have only a "negligible impact" on their annual rate of survival.

The agency concluded that on-shore oil company activity would not be near polar bear dens or walrus haulouts — or gatherings — and that offshore drilling would occur during the open water season, not near pack ice used by polar bears and walrus.

The disputed rules cover five years ending in 2012. Rules for the next five years are being drafted, Woods said.