Thousands of dead anchovies washed ashore on the Bolinas Lagoon shore in Marin County, California, earlier this week, according to photos and video shared with ABC San Francisco station KGO.
"This is just one of those times where we kind of get to see just the sheer number of the size of these schools of fish," Marin County Parks director Max Korten told KGO. "So it's kind of amazing."
There is still uncertainty about why the fish washed up on the shore. Referencing biologists, Korten explained, "What likely happened is, you know, some kind of predator out in the ocean encountered a school of anchovy somewhere near the mouth of Bolinas Lagoon," according to KGO.
He said this possibly pushed the anchovy more toward the shallow water, where they sucked up the limited oxygen and suffocated, according to KGO.
A volunteer researcher told KGO News the anchovy could have been going where the food is.
Jim Ervin also told KGO this La Nina year is generating more food production and the foraging fish are following. He explained the cool water is bringing in more anchovy than seen in the last 10 years off the coast and in the bay.
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Ervin said seabirds are feasting. "There's more fish than they know what to do with," he told KGO.
Officials said there is no reason to panic over the mass die-off, saying similar events have happened several times over the last few decades.
"My biggest words of assurance, I guess, is that anchovy populations boom and bust," Ervin told KGO. "And we're in a boom year. Then things like that, they drive 'em into the shore and unfortunately they do themselves in sometimes."
Korten with Marin County Parks told KGO that the Bolinas Lagoon as a pretty fragile ecosystem and is encouraging anyone wanting to see the anchovies, to be mindful of the environment.
"It's a home to a really abundant amount of marine life," he said. "We just asked if anybody goes near there, just use caution and not to disturb the animals, the seals and things that make their home there."
ABC News' Amanda del Castillo, Jeffrey Cook and Jennifer Metz contributed to this report.