A juvenile salmon shark was stranded near Sunset Beach in northwest Oregon on Saturday, prompting a rescue operation that ultimately ended with the shark dying a few hours later at Seaside Aquarium.

An Astoria man saw the struggling 31⁄2-foot shark in the surf and called the aquarium to see if anyone could help. Attempts to return the shark to the ocean by taking the shark back into the surf failed and the shark kept returning to shore, staff of the Seaside Aquarium said in a Facebook post.

Aquarium staff worked to get the shark into a holding tank so it could be transfered to the aquarium, and then, eventually, to a bigger facility with larger tanks for rehabilitation.

The attempt was not successful, and the shark died a few hours later. It is not uncommon for juvenile salmon sharks to strand themselves this time of year, aquarium staff said. Salmon sharks that beach themselves rarely survive the ordeal.

The reason for juvenile sharks washing ashore this time of year remains a mystery, aquarium staff said. The animals are often mistakenly reported as “baby great white sharks,” aquarium staff said, which is to be expected when the two species only have a couple of small identification clues to separate them.

“The aquarium often tries to collect those which have passed away. We use them for education, allowing people to watch the dissections, while we take tissue samples which are sent off to biologist(s) studying this phenomena,” the staff said in a Facebook post.