A cross-section shows the inner structure of a tail fin recovered from a thresher shark that washed up near Cranberry beach approach in mid-August.

OCEAN PARK — Peninsula beachgoers on Sept. 2 encountered the second large shark to come ashore in as many weeks.

The latest one was still alive when Seaside Aquarium staff arrived, but died shortly after.

“With some much-needed help, volunteers and staff were able to recover the shark, which weighed anywhere from 300 to 365 pounds,” the aquarium said in a statement. The Seaside facility responds to significant strandings and finds of marine creatures in our area.

Like a 12-foot thresher shark that washed ashore on Aug. 18, the latest one was too big to freeze. A necropsy was scheduled for Sept. 3.

“We really wanted this to be a learning experience for people,” aquarium staff said. “It is not very often that we get to see these large sharks, and anything we can learn or educate the public on is a great opportunity.”

Researchers ended up with an audience of about 50-75 people.

“People were really interested and asked a lot of great questions,” staff said. “Most people were fascinated by the length of the shark’s tail, in which it is named after. The thresher shark uses its long tail to ‘thrash’ through schools of fish, stunning them, then swimming back through and eating the stunned fish.”

The female thresher shark found onshore in August was discovered near Cranberry beach approach. By the time aquarium staff arrived, someone had cut off the dorsal fin and removed the jaws — which is not illegal but does compromise scientific data. The shark was too big to freeze, so the decision was made to dissect the shark that day.

It is unknown why these sharks are washing in. Aquarium staffers ruled out fishing-vessel interactions as a possible cause of death.

Staff took various external and internal measurements along with tissue and organ samples, which were sent to Taylor Chapple at Oregon State University. He is studying regional sharks.

Thresher sharks follow the warm water currents off of the Oregon and Washington coast during the summer months. They can reach up to about 18 feet. Like salmon sharks and great whites, they are able to raise their body temperature above the ambient water temperature.

To learn more, see marineresearch.oregonstate.edu/big-fish.