Hollywood screenwriter James Hart knew he was on to a good thing when he got his invite to BIFF this year.

It gave him an opportunity to research something close to his heart — how Bermuda is coping with its lionfish problem.

The New York resident’s plan was to share the information with his beloved Cayman Islands in the hope of reducing the population of the invasive species there.

“I’m part of a non-profit organisation, Lionfish University, that I cofounded with Stacy Frank and Courtney Platt in Cayman two years ago,” said Mr Hart.

“We did it out of the need to create a platform where information could be exchanged.

“It’s a huge problem [there] and Bermuda has been the other hot spot.”

His initial interest in the species was completely “mercenary”, the screenwriter and producer of such films as Hook!, Bram Stoker’s Dracula and Contact admitted.

“I wanted to write [a version of the Syfy hit] Sharknado, for lionfish. In 2010 nobody knew what lionfish were.”

Research showed lionfish were depleting native fish stocks and killing coral reefs in the Caribbean Sea, Atlantic Ocean and Gulf of Mexico.

What grabbed Mr Hart most was the impact they were having on waters around the Cayman Islands, where he frequently went diving.

“Our research found a need to address the problem and bring it to public view,” he said. “In Little Cayman they began a culling project, working with the Central Caribbean Maritime Institute, to promote lionfish research of all trap programmes. The first was in Bermuda.

“So I’m here for the film festival but I’m really here for Lionfish University.”

Lionfish were first spotted in Bermuda’s waters about 15 years ago. Lobster fishermen have had some success in catching them; work continues to create a lionfish-specific trap.

“I hope to take some experience and knowledge back to Cayman, where we’re trying to start community culling,” Mr Hart said.

“It’s been very successful but traps, if they work, would enable us to do it better. We’re never gonna get rid of them but we can try to contain the population as much as possible.”

One of his great successes came while diving in Cayman in January, GoPro in hand.

“It was a pretty non-eventful dive,” he said. “I hadn’t seen any lionfish.

“We were headed to the safety spot and we saw a goatfish behaving strangely. It was the most exciting thing we’d seen on the dive so I went back down.”

Then, he spotted a lionfish and a Nassau grouper.

“He comes in and tries to corral the lionfish to get an angle where I hoped it would eat it,” Mr Hart explained. “Another grouper came and was herding, something I’d never seen before.

“I was almost out of air, I was 50 feet down and the first grouper starts herding.”

As a diver, he found what he was witnessing fascinating.

“Normally, the fish wait for the diver to do something,” he explained. “I’m witnessing something I can’t believe I’m seeing.

“I can see my dive buddies watching me and I’m thinking, please eat it before I run out of batteries, out of film, out of air, out of everything.

“I have to hand it to the grouper, he stayed with the lionfish.”

The grouper waited until they were 15 feet from the ocean surface before it made its move.

“He nipped the lionfish on the dorsal fin so it turned and then he came and took it. I couldn’t see any evidence of it releasing the lionfish.

“I watched as long as I could, but finally had to turn the camera off and surface. I got to the boat and checked the video and it was all there.”

Mr Hart acknowledged that he was not an expert but said he had learned a lot about lionfish behaviour through his work with Lionfish University.

“I’d never seen one operate this independent and this determined to take the lionfish to lunch and eat it,” he said.

He later shared the video with “noted lionfish people” at Cayman’s Southern Cross Club. “I’ve done 12 movies and three royal premieres,” he said. “I’ve had big successes and big failures but never had a premiere like this.

“It was watched ten or 12 times that night. There’s been some criticism that there was diver interaction, but the grouper didn’t wait for me to do its job.

“A couple of people said they had seen a grouper eat a lionfish but it’s definitely not been documented. A grouper eating a lionfish is not news but nobody had produced a video that was so complete.”

Mr Hart spoke on character development at a script-writing workshop held on Saturday as part of the 18th Bermuda International Film Festival.