Sea otters are now free to roam about Southern California waters with equal protection under federal wildlife laws with the end of a 25-year-old no-otter zone.

The U.S. Fish and Wildlife Service, in a move applauded by otter advocates, published a rule this week ending a no-otter zone south of Point Conception that was part of a 1986 plan to establish a reserve population of otters on one of the Channel Islands.

"Sea otters will now have the same protection statewide," said Steve Shimek of the Otter Project, which sued the federal wildlife agency in 2009 to terminate the sea otter translocation program.

The original plan was to create a backup population of sea otters on San Nicolas Island, the most remote of the Channel Islands, that could reestablish the coastal otter population if it was decimated by an oil spill.

But the translocation plan never worked. All but a dozen of 140 otters swam away from San Nicolas Island, back to their home waters or to perish. But the no-otter zone, established at the behest of the offshore oil industry, shellfish fishermen and the Navy, remained on the books.

That gave otters that migrated into the zone less protection under the Marine Mammal Protection Act and Endangered Species Act than otters north of zone, Shimek said.

In fact, otters haven't been removed from the zone for a number of years, he said, but abandonment of the no-otter zone on "paper" will guarantee otters "the same protection statewide."

Andy Johnson, sea otter program manager for the Monterey Bay Aquarium, said there are about 50 otters now on San Nicolas Island, and the range of the southern sea otter has expanded from Santa Barbara County to Half Moon Bay.

The otters once naturally ranged from Baja California to Alaska before they were nearly hunted to extinction by 19th-century fur traders.

The coastal otter population is now estimated to be about 2,800, and the animal is considered threatened under the federal Endangered Species Act and "depleted" under the Marine Mammal Protection Act.

Johnson said getting the no-otter zone removed has been a long process that lasted more than a decade. "This is the final step," he said.

In practical terms, he said, not much will change because the no-otter zone early on was found to be impractical.

The translocation program itself was controversial but believed to be warranted by the potential threat of a catastrophic oil spill. "In hindsight it was not the best idea in the world," Johnson said.

While oil spills still could pose "a huge threat" all marine wildlife, Johnson said with otters, "We have seen enough range expansion that a single spill would probably not cause catastrophic damage to otters."

The mainland population began to expand in the 1990s and about 150 otters swam across the no-otter line. Fishermen unsuccessfully sued the federal wildlife agency, demanding that the otters be trapped and removed.

In 2001, the agency said it would no longer move otters out of the zone, but left the lower level of protection in place for otters in the southern waters, the Otter Project said.