Two Florida scuba divers who were on a dive beneath Palm Beach County’s Blue Heron Bridge during the Thanksgiving holiday spotted a bright yellow fish approximately four inches long that they had never seen before.

Although some divers might have just admired it, taken a photo and kept on swimming, Deb Devers and Lureen Ferretti reported it to the Reef Environmental Education Foundation (REEF) — a Key Largo-based non-profit organization that serves as a regional clearinghouse for control of exotic marine fish species.

“They weren’t sure what it was, but they knew it was something that doesn’t belong here,” said Las Akins, director of special projects for REEF.

Akins said their instincts were correct: the fish was a mimic lemon peel surgeonfish, also known as a chocolate surgeonfish, native to the Indo-Pacific and the first of its kind documented in Florida waters. Devers kept track of the fish, and last month, she and Akins captured it alive using hand nets. It was sent to the Ripley’s Aquarium of Canada to be displayed as an educational tool on the hazards of invasive species.

Akins said the removal might have averted an ecological disaster similar to the spread of lionfish — another Indo-Pacific invader now well-established in the Western Atlantic, Gulf of Mexico and Caribbean. Lionfish — first sighted off Dania Beach in 1985 and believed to be an abandoned aquarium pet — have been blamed for wiping some local reef systems clean of native tropical fish.

“We don’t know what the effects would have been if the fish had become established and began reproducing,” said Akins. “But if we wait to find out, then it’s too late.”

According to REEF, taking out the surgeonfish was the third successful preemptive strike against a non-native marine fish species in Florida coastal waters.

In 1999 and 2002, REEF staff and volunteers captured four large Indo-Pacific batfish from Molasses Reef in Key Largo. In 2009, they removed a whitetail dascyllus damselfish from the east side of the Blue Heron Bridge. In 2012, Miami divers Greg Caterino and Wayne Grammes speared an exotic humpback grouper on a reef off Biscayne National Park and turned the carcass over to REEF. Akins said none of those three species are known to have reappeared in Florida waters since their removals.

“Some people might say, ‘Oh big deal, we took this little fish out of the water,’” Akins said. “But that’s the way the lionfish got started. If only we could have taken the first few lionfish out of the water in the first place. We’re relying on divers, snorkelers and fishermen to be our eyes and ears on the water. It’s a perfect example of how early detection and rapid removal can be successful in stemming an invasion.”

Releasing non-native fish into Florida waters not only is harmful, but also illegal. The Florida Fish and Wildlife Conservation Commission encourages pet owners who need to find new homes for their fish or other exotic animals to call the FWC’s Exotic Species Hotline at 1-888-IveGot1.

Anyone who spots a strange-looking fish that they suspect is invasive is advised to take a photo and report the sighting at reef.org.