The South Side Shark Symposium is April 10. File/Provided

Officials are investigating whether some federally protected shark species were caught and kept as trophies during an Edisto Beach fishing tournament.

Shark pictures posted on Facebook reportedly prompted the probe.

"Once people saw the photos on social media, they started calling with their concerns," state Department of Natural Resources  spokeswoman Kyndel McConchie said.

"Once our officers saw the photos, they called a rep from the National Oceanic and Atmospheric Administration and we started working together to launch the investigation," she said in an email.

The shark fishing tournament was held on June 10.

Federally protected shark species must be released back into the sea if they are caught.

The Charlotte Observer quoted an official who said the photos appeared to show a dusky shark and two sandbar sharks. Both dusky and sandbar sharks are protected under federal law.

McConchie said she could not confirm that information because the species of shark is part of the investigation, along with the number of boats involved.

Potential penalties for catching and keeping protected shark species range from $2,000 to $100,000, she said.

The National Marine Fisheries division of NOAA and DNR are conducting the investigation. A spokesman for NMFS could not be reached Tuesday.

Dillard Young, owner of tournament organizer Edisto Watersports and Tackle, told the Observer he thought the fishermen who brought in the suspect sharks confused their species.

"We go over all the rules, and everybody's supposed to abide by the rules," he said. "Those guys were smart enough that if they thought they had an illegal shark they wouldn't put it on the scale."

Thirteen sharks were landed during the tournament, an annual event since 2010. The winner was a 956-pound tiger shark.

Tiger sharks are legal to catch and keep if they are at least 54 inches long, officials said.

A picture of an unidentified shark weighing 220 pounds was posted Tuesday on the Facebook page for Edisto Watersports and Tackle.

Young, the owner, was not available for comment Tuesday because he was out on a boat, an employee said.

Some 21 shark species are protected under federal law.

Sharks are particularly vulnerable to overfishing because they don't reproduce rapidly, according to experts, and take years to reach sexual maturity. They have long gestation periods and produce few offspring, according to experts.