A KHON2 viewer shared video taken Monday of thousands of dead crabs that washed up onto North Shore beaches.
They were spotted at the popular surf spots "Backyards" and "Off the Wall" Monday, and along Mokuleia Tuesday morning.
The crabs are all gone now, but there were thousands of them just the day before. They were small with large eyes, and were spotted during high tide.
Visitor Kenrae Dorsey saw "lots of little crabs in clusters up the whole shore."
Waialua resident April Woolley said she "was at the beach with my son this morning, and I had just seen all these cleanish, little pinkish crabs or lobsters. I didn't know what they were."
Andrew Rossiter, director of the Waikiki Aquarium, says they were juvenile crabs, likely washed up after strong winds and currents. He says at this stage in their life cycle, they live offshore as plankton.
"It's either very strong ocean currents or abnormal weather with winds that sweep them on shore. They're usually found in shells, if you like, and then they get washed on shore in a big mass," said Rossiter.
He says a similar event happened five years ago on Oahu following a few days of strong onshore winds.
The Department of Land and Natural Resources' Division of Aquatic Resources told us this type of thing happens when there's a spawning event in the ocean and new hatchlings get tossed around the waves.
DLNR says events like this happen about every four years.