When one of the ocean's top predators washes up dead on a beach, it's likely that something fishy must have happened. On Sunday (June 17), beachgoers found a juvenile male great white shark (Carcharodon carcharias), weighing 500 lbs. (225 kilograms) and reaching 8 feet (2.4 meters) long, on Beer Can Beach in Aptos, California, near Santa Cruz, reported KION.

But authorities aren't disclosing the shark's cause of death, and it's now the subject of a law enforcement investigation by the California Department of Fish and Wildlife (CDFW).

KION reported the male shark appeared healthy besides a few relatively minor lacerations, possibly caused by sea lions. But it's unclear if those scratches caused the creature's death, KION reported.

Researchers from CDFW collected the shark on Sunday afternoon and performed a necropsy at the Long Marine Lab in Santa Cruz on Tuesday (June 19), but they aren't revealing what they found. "Upon receiving the lab's necropsy results, the CDFW's Law Enforcement Division is now taking up the investigation," a representative from CDFW told Live Science in an email. The representative declined to comment further. [See Photos of the Great White Shark on Beer Can Beach]

It's not a frequent occurrence for great white sharks to wash ashore, although one washed up in the same area last year. "The white shark population has been essentially booming off the California coast," said David Ebert, a shark scientist and the director of the Pacific Shark Research Center at Moss Landing Marine Laboratory in Moss Landing, California. "It wouldn't be unexpected that occasionally one would wash up," he said.

Great white sharks are classified as vulnerable by the International Union for Conservation of Nature. But great white shark populations have been making a comeback since about 1972, when the Marine Mammal Protection Act was passed, said George Burgess, a marine biologist and director emeritus of the Florida Program for Shark Research at the University of Florida. The act made it illegal to harm any marine mammal, including seals and sea lions, that makes up the great white shark's main food source. And, because they're classified as vulnerable, great whites are illegal to catch without a special permit.

What could kill such a beast?

Great white sharks don't usually have predators, except for occasional attacks by killer whales (Orcinus orca), Burgess said. "Killer whales tend to go for the belly and eviscerate the white shark," Burgess told Live Science. But the midsection of this great white shark was intact, and there were no major lacerations apparent in photos. [Photos: Orcas Are Chowing Down on Great-White-Shark Organs]

The great white that washed up dead in the same area last year had a bacterial brain infection that also affects salmon sharks (Lamna ditropis) and thresher sharks (Alopias species), Ebert said. It's unclear how the sharks get infected with brain bacteria, but it's a significant cause of death in salmon sharks along the California and Oregon coasts, scientists reported in a 2012 study in the journal Veterinary Pathology.

Humans are capable of killing a great white shark, but that's infrequent, Ebert said. "They're not taken often in fisheries," he said. "It's a good size animal, so it's not the kind of thing that someone's likely to try to catch." There is an allowance for accidentally catching a white shark that gets entangled in a fishing net, he said, but it's illegal to target them.

Some fishermen might be tempted to catch a great white shark, though, because shark fins are a delicacy in Chinese culture and elsewhere. "Those fins are worth a great deal of money, and, if they were sold on the black market, they could have made a real pretty penny," Burgess said. This shark still had all its fins, so Burgess wonders if it was caught accidently in a fishing net and then thrown back in the water by someone who didn't know what else to do.

Ebert said he's "not aware of any other instances in California where a white shark washing up has led to a criminal investigation."

Neither of the experienced shark researchers has any clue as to why the CDFW's Law Enforcement Division is investigating the shark's death. But, Burgess said, "If this was a result of human interaction, it had to be illegal."

Original article on Live Science.