PORTLAND, Ore. (Reuters) - Federal fishery managers have banned nearly all sardine fishing off the U.S. West Coast for the second straight year in a move hailed by conservation groups as key to protecting decimated California sea lion herds.

A man holds a tray of sardines in Costa Mesa, California November 17, 2014. REUTERS/Lucy Nicholson

Pacific sardine populations have plunged by 90 percent since 2007, prompting the Pacific Fishery Management Council to vote Sunday to extend its prohibition on virtually all fishing of the small oily fish within 200 miles of the California, Oregon and Washington coasts.

The sardine collapse has rippled up the food chain and has been linked to deaths of sea lions and brown pelicans across the U.S. West Coast. Sea lion pups, emaciated and starving, have washed up on California beaches.

“Their mothers can’t find enough food, and have to search further and further for longer and longer periods of time,” said Ben Enticknap of Portland-based environmental advocacy group Oceana.

The El Nino ocean warming phenomenon as well as normal multi-decade ocean cycles, are factors in the decline of the sardine population, said Enticknap, whose nonprofit is urging regulators to adopt a longer-term approach to addressing sardine populations. Climate change may also play a role, he said.

“If you are fishing that population too hard as it is crashing, the science shows that will drive those populations down more quickly,” he said.

Michael Milstein, a spokesman for the National Oceanic and Atmospheric Administration, said the fisheries council had already started restricting sardine harvest before imposing a near-moratorium last year – and that those early efforts may be paying off.

“There are some indications that large numbers of sardines did spawn successfully last year,” Milstein said. “But we won’t know what difference that makes until those juvenile fish survive for a few more years.”

Most sardines caught off the U.S. West Coast are sold into global commodity markets, either canned for human consumption or sold as feed for penned tuna, with very little sold fresh in local markets, Oceana said.

The moratorium on sardine catching includes exceptions for limited fishing by the Quinault Indian Nation, and for small numbers of sardines accidentally caught alongside other fish.