No one is sure why, but thousands of juvenile crabs are washing up on Oahu's shores.

Reports are coming in from Kaimana Beach to Kahala on the south shores, as well as areas from Windward Oahu from Kaneohe to Ka'a'awa.

The Waikiki Aquarium says it is fielding calls and emails about the unusual occurance since Thursday.

Scientists believe they are what's known as 7-11 crabs which are native to Hawaii.  The mystery remains -- why are so many turning up now?

"It's probably something ecological because it's happening on such a large scale," said Waikiki Aquarium Director Andrew Rossiter.  "You say it's pollution or it may be a pulse of warm water, or a pulse of cold.  If it were any of these three it would happen to other species as well, but in this case, it's just the 7-11 crab."

Rossiter says the crabs can grow to be quite large and can be eaten by humans.  But, many won't survive because fish or birds will eat them as they wash up on the shore.