An invisible line in the ocean is now gone. For the past 25 years, sea otters that swam further south than California's Point Conception were scooped up and moved back north, where they could not interfere with fishermen or oil interests along the southern coast. After years of debate, this controversial "No-Otter Zone" was lifted by the U.S. Fish and Wildlife Service (FWS) on Dec. 18, and sea otters are now free to reclaim their historic territory.

Southern sea otters came very close to extinction a century ago after intensive hunting for their fur reduced their population to just 50 animals living off the coast of Big Sur. Today about 2,800 live in California waters, a testament to decades of protection under the Endangered Species Act (ESA), the U.S. Marine Mammal Protection Act (MMPA) and California state law.

But while these laws have protected the sea otters and given them a chance to recover their population, it also forbid them from traveling too far south in search of food. This zone was established in 1987 when the FWS was trying to establish a small population of sea otters on remote San Nicholas Island, which was intended to act as a safety net in case the main population further north was hit by an oil spill or other catastrophic event. Under the ESA and MMPA, moving the sea otters to San Nichols Island required special permission of the U.S. Congress. According to the advocacy organization The Otter Project, "an agreement was reached between FWS, conservationists, commercial fishermen, the Navy and the oil industry to create a sea otter 'management zone,' dubbed the 'No-Otter Zone', from Point Conception to the border of Mexico, requiring FWS to remove otters from the zone." This also meant that sea otters lost some of their ESA protections and the FWS lost oversight of otters within this zone.

FWS stopped moving otters out of the zone more than a decade ago, mostly because the San Nicholas Island population did not thrive, but it took years for the zone to officially be lifted. Meanwhile, sea otters from the north were increasingly crossing the line, angering fishermen who — as I wrote in 2010 — feared that the voracious mammals would eat up their profits.

Steve Shimek, executive director of the Otter Project, told local news station KSBW that the zone was never effective. "Trying to tell a marine mammal to stay on one side of an imaginary line across the water was a dumb idea," he said, pointing out that the now-increased territory is essential to the otters' population growth. "Allowing otters to once again inhabit Southern California waters is considered critical to the recovery of the species."

Not everyone is happy about the zone being lifted. California Republicans sponsored a bill in April to keep the "no-otter zone" in place, arguing the creatures would "be invading prime shellfish fishing grounds and U.S. Naval testing areas." That bill never got off the ground, and now the sea otters have more ocean waters in which to swim, eat and, hopefully, thrive.

Related posts on MNN:

A legal victory for sea otters: 'No-Otter Zone' finally lifted in California
Sea otters are now free to reclaim their historic habitat in areas previously reserved for fishermen and oil companies.