A skate, one of the many attractions at the Seaside Aquarium.

Skate egg casings have been washing onto the North Coast’s sandy beaches, some with embryos developing inside of them, reports Tiffany Boothe of the Seaside Aquarium.

About a foot in length and resembling a chunk of seaweed, egg casings are produced by the female skate and after fertilization are deposited on the ocean floor,

The casings will only wash back in if thrown back, Boothe said, but an egg casing can be brought to the aquarium and put into a protected saltwater tank and continue to incubate.

A single casing can have anywhere from one to seven embryos inside. If stranded on the beach the casings will dry up and the embryos inside will perish. Once hatched, they can be released back into the ocean.

The most common skate egg casing to come across on Oregon shores are produced by big skates. Big skates are the largest skates in the world, growing 8 feet in length and weigh up to 200 pounds.