A four-metre shark which washed ashore at Coronation Beach, about 28km north of Geraldton, on Tuesday had a big sea lion stuck in its throat.
The discovery was made during a Department of Fisheries investigation into the tagged great white’s death, which is now complete.
Principal research scientist Rory McAuley said the shark had no visible signs of injury or disease, but the presence of the Australian sea lion could explain why the shark was behaving strangely.
The shark was filmed by a number of bystanders on Saturday as it swam into the shallows, beaching itself and thrashing about a few metres from the shore.
"Such a large object may have damaged the shark’s internal organs or impeded water flow into his gills, contributing to his death," Dr McAuley said.
"Alternatively, the shark may have accidentally become stranded in his attempts to get rid of the obstruction."
The department said the shark was tagged in South Australia in January this year.
"Confirmation of when and where this shark was tagged demonstrates the extraordinarily mobile nature of this species," Dr McAuley said.