Jeff Barnard / The Associated Press

GRANTS PASS — Millions of krill — a tiny shrimp-like animal that is a cornerstone of the ocean food web — have been washing up on beaches in Southern Oregon and Northern California for the past few weeks.

Scientists are not sure why.

National Oceanic and Atmospheric Administration oceanographer Bill Peterson says they may have been blown into the surf by strong winds while mating near the surface, and then been dashed on the beach.

The species is Thysanoessa spinifera. They are about an inch long and live in shallower water along the Continental Shelf. They have been seen in swaths 5 feet wide, stretching for miles on beaches from Bodega Bay, Calif., to Newport, Ore. Some were still alive.

“There has definitely been something going on,” Peterson said from Newport.

They may have fallen victim to low levels of oxygen in the water, said Joe Tyburczy, a scientist with California Sea Grant Extension in Eureka. A recent ocean survey showed lower than normal oxygen levels in some locations. If the krill went to the surface to get oxygen, they could have been blown on shore, he said.

The mass strandings are unusual, but not unheard of, Peterson added.