The Lionfish invasion: Are we seeing a decline?

Lionfish numbers appear to be on the decline.

In its November tournament, Cayman United Lionfish League rounded up 545 lionfish, far from the tournament record of more than 1360 set in one of the organisation’s early tournaments.

Many cullers in Cayman waters are reporting that lionfish are becoming harder to find. So what’s happening?

Last summer, Cayman 27 reporter and lionfish culling enthusiast (and author of this article) Joe Avary once could practically guarantee a haul of 10 to 20 pounds of lionfish for a day of hunting the reefs. Now he calls himself lucky if he gets more than five pounds for a day’s fishing.

From a non-scientist’s point of view, it certainly appears something is happening within the lionfish population, and it also appears that actual scientists could be starting to see it too.

Earlier this month, the Central Caribbean Marine Institute shared findings from phase one of its novel lionfish tagging survey. Dr. Alli Candelmo of CCMI told Cayman 27 the study, which involved surgically inserting tags into sedated lionfish on the reef, revealed evidence of predation.

But can predation alone explain the decrease in lionfish that has been reported anecdotally?

That’s one question posed this weekend on a conference call with Lionfish University’s Stacy Frank and Jim Hart, and a top marine scientist with the National Oceanic and Atmospheric Administration in the US.

Are lionfish numbers on the decline? It’s a question many in the culling community have asked after finding less and less of these invasive predators in recent months.

“This is a big question out there right now: has nature figured this out, or is culling really as effective as it looks to be in places where it is taking place,” said Dr. Steve Gittings is Chief Scientist for NOAA’s National Marine Sanctuary System.

He spoke with Cayman 27 via teleconference, hosted by Lionfish University’s Ms. Frank and Mr. Hart over the weekend.

In the discussion, he said the results from CCMI’s aforementioned lionfish tagging project, which showed evidence of predation were certainly interesting. But he added that it’s far from concrete proof that native species are recognizing lionfish as food.

“It could easily be that they were acting like injured fish, because of the way that they were released,” theorised Dr. Gittings of the post-surgical lionfish’s behaviour.

Ms. Candelmo told Cayman 27 earlier in January that another 30 tags are to be deployed in phase two of CCMI’s survey. She indicated that this time, the lionfish will be sequestered post-surgery to allow for recovery before release into the natural environment.

Videos of predation have surfaced before. One video taken by Lionfish University’s Mr. Hart back in early 2015, depicted what is believed to be the first documented open-water kill of a lionfish by a grouper.

“I will freely admit that my internal voice was yelling at that group or to eat the lionfish,” laughed Mr. Hart, recalling the encounter. 

But if the drop in lionfish population is not due to natural predation, or culling, could it be attributable to something else?

The DOE told Cayman 27 a number of lionfish displaying curious lesions have recently been detected in Cayman’s waters. He said a number of such specimens were found in CULL’s November tournament and sent to a parasitologist in St. Kitts for further examination.

Dr. Gittings has seen evidence of lionfish on the western Florida shelf with similar abnormalities.

“It could be either parasites, or viruses, or other forms of disease that are starting to take hold in lionfish population that didn’t before,” he suggested.

While the scientific community searches for answers, Mr. Gittings urged lionfish cullers to report any evidence, video or otherwise, of natural predation.

“We are still not there to proving any kind of natural mortality, other than one little video, which still had a diver involved in it that may have influenced the behavior of the grouper,” said Dr. Gittings.

Dr. Gittings said as long as the invasive lionfish exists in the Caribbean, it will continue to eat the small prey fish that adult grouper and snapper rely upon, and juveniles of those same species as well.