EUREKA -- Scientists are trying to determine what caused millions of shrimp-like critters known as krill to die and wash ashore along 250 miles of coast from northern California to southern Oregon last month.

The Santa Rosa Press Democrat (http://bit.ly/12NSJSG ) reports one theory is that a shift in winds caught the animals near the ocean surface and caused them to be swept ashore.

"Once they get into the surf line they are in trouble," said Joe Tyburczy, a scientist with the California Sea Grant Extension in Eureka, a coordinator of the investigation.

Scientists say the strandings were reported from Newport, Ore., to McKinleyville in northern Humboldt County in mid-June, making it the geographically largest krill die-off on record.

An examination of 10 krill found all were female and most carried sperm packets, suggesting they may have perished just after mating, Tyburczy said.

According to data from offshore ocean buoys, the wind rapidly shifted from the northwest to the southwest just before the strandings, pushing surface waters toward the shore, Tyburczy said.

In Redwood National Park, dead and live krill formed a mile-long pink band on the sand bear Redwood Creek on June 17, according to David Anderson, fishery biologist at Redwood National and State Parks.

Scientists and fishermen have noted an abundance of krill this year, drawing drawn large numbers of whales and salmon this year. A key part of the marine food chain, krill is sustained by cold, nutrient-rich waters that are brought to the ocean's surface by strong winds.

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Information from: The Santa Rosa Press Democrat, http://www.pressdemocrat.com