VENTURA, Calif. (AP) _ The southern sea otter population between Santa Cruz and Point Conception has fallen 12 percent over the past year, and scientists are puzzled.

``We're going to have to pay close attention to what's happening. We can't point our finger at any one thing,'' said Carl Benz, assistant field supervisor for species listing and recovery in the U.S. Fish and Wildlife Service office in Ventura.

Disease and pollution are suspected, Benz said.

``They are at the top of the food chain. That tells you something is wrong with our marine environment,'' said Jeff Calder, executive director of Friends of the Sea Otter.

The fall census of the southern sea otters found 1,937, down 12 percent from last fall and just above the 1,850 threshold for listing them as endangered. Several years ago, southern sea otters numbered well above 2,000 along the 200-mile stretch of coast.

Southern sea otters are one of 13 otter species worldwide.