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Clam surfacing phenomenon prompts advisory at the Oceano Dunes

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Posted at 9:50 PM, Dec 28, 2022

An increase in the clam population has prompted officials to restrict beach access for vehicles at the Oceano Dunes.

Drivers at the dunes are being asked to only drive on dry sand because wildlife experts are seeing clams coming to the surface near the shoreline.

The Pismo Clam has seen a major population rebound in recent years, but a new phenomenon is causing some concern.

“We started seeing clams coming to the surface in 2021,” said Stephanie Little, senior environmental scientist at the Oceano Dunes District.

Clams that are usually buried beneath the sand at the shoreline are now coming to the surface, and scientists don’t know why.

“Honestly, we do not know what is causing it. The one thing we have noticed is that it tends to be the middle size of the population. So, something like 3, 4, 5 inches—kind of the mid-size clams. We’re not seeing the small ones doing it and we don’t see the big ones doing it,” said Benjamin Ruttenberg, director of Cal Poly’s Center for Coastal Marine Sciences.

Clams started coming to the surface again in recent weeks, prompting the current advisory.

“It’s hard to know if and when this issue is going to go away, but we’re doing our best to respond accordingly and put the signs out in areas where we’re seeing the clams surfacing,” explained little.

Officials are urging the use of either all-wheel or four-wheel drive as drivers avoid the immediate shoreline and stick closer to the sand dunes.

“I’ve got a big 4-wheel drive--I can probably handle it,” said Scott Webb who is visiting the Central Coast from Roseville.” I think it’s a good idea to take care of the wildlife in any way we can.”

State parks officials say this is about striking the right balance between allowing beach access and protecting an iconic species.

“It is quite exciting that they are coming back,” said Little.

Pismo Beach was once a world-famous clamming destination until the population was nearly wiped out.

Researchers at Cal Poly say the population has made a major comeback since they started monitoring the Pismo Clams in 2015.

“We’d go out and spend three or four hours doing surveys and find nothing. I’d have to tell them that zeroes are still data,” said Ruttenberg. “Now, in a single survey, we will find sometimes tens of thousands of clams.”

The California Department of Fish and Wildlife asks anyone who finds a clam on the surface to carefully rebury it.

Researchers say that shellfish poisoning from algae blooms could be a cause. Other theories are that oxygen depletion or a lack of food are causing clams to surface. The team of Cal Poly researchers is tagging clams with QR codes that people can scan and then report back information that will help scientists understand what is happening with the population.