Seafood fans sometimes find live crabs inside their oysters. The good, bad and — lucky?

Seafood fans may be surprised by the sight of a pair of tiny claws wiggling around in their oysters, but it’s a more common occurrence than many would think.

Raw oyster fans might consider the finding a testament to the freshness of their seafood. Others consider it a symbol of good luck. One woman on vacation to North Myrtle Beach this past summer was taken aback by the discovery before her father ate the entire oyster — crab and all.

“I suddenly saw a small claw reach out of the oyster!” Beth Troutman told The Sun News in August. Taken aback by the sight, she checked “to make sure my eyes weren’t playing tricks.”

The restaurant’s waiter told Troutman’s family the crab was “considered a delicacy and a good omen for the lucky diner who finds it.”

But how rare is the finding?

The pea crab is a parasite of the eastern American oyster crab. Pea crabs live inside the gills of oysters.

William Ambrose, vice dean of the school of the coastal environment and professor of marine science at Coastal Carolina University, said anywhere from 1% to 10% of oysters typically have crabs living inside of them, depending on geographic location.

Ambrose cited a study published in 2015 in the Journal of Shellfish Research.

The study, titled Oyster Utilization and Host Variation of the Oyster Pea Crab, examined the frequency of occurrence and impact of pea crabs on adult oysters from natural intertidal reefs in Hewletts Creek in Wilmington, N.C., and artificially-created intertidal reefs from Jones Island, N.C.

Researchers examined oysters from July to October 2013.

They found that the occurrence of pea crabs in adult oysters living in natural reefs was low, ranging from 1-4% of oysters. In artificially created reefs, the occurrence of pea crabs was higher, with the parasites being found in about 10% of the sampled oysters.

Pea crabs were far more common in juvenile oysters, with researchers finding them in roughly 23% to 28% of young oysters.

With declining oyster populations, however, pea crabs have been forced to find alternate hosts, the study states. Alternative hosts for pea crabs include jingle shells, blue mussels and ribbed mussels.

The relationship between the pea crab and the oyster has been described by marine scientists as parasitic “because [the pea crab] inhabits live oysters, presumably scraping food particles off the gills, damaging them, and subsequently reducing oyster conditions.”

The good-luck superstition isn’t mentioned in the study — that’s up to the diner to decide.

“As far as luck goes, they say they are lucky even if you don’t believe they are,” Ambrose said.