The ‘unsung heroes’ of Little Cayman

Of an evening on Little Cayman, our habit is to watch the sunset from the pier, as frigates and boobies hightail it back from open water to roost as the light fades and the moon rises over Owen Island.

That serene view is different on Wednesdays at dusk. A stream of dive masters appears, lugging their gear down to a dive boat, heading out to cull the invasive lionfish. (Island dive operators take turns providing the boat; the divers are volunteers certified by the Department of the Environment, as spearing is otherwise illegal in the marine park.) After working all day leading dives and humping tanks, these dedicated dive professionals get back in the water one more time to tackle the lionfish problem head on.

There is no way to patrol the entire island. Lionfish are found from the shallows to depths no diver could safely reach. But the goal is to keep the numbers down in the Bloody Bay Marine Park, to provide an ark, a sanctuary for their prey. And so the dive masters persevere, week in, week out, with little acknowledgment or thanks, doing what they can to protect the reef they love.

Recent research happily confirms the wisdom of this strategy. It isn’t necessary to kill all the lionfish in an area; reducing their numbers by 75 percent allows for their prey to rebound completely.

A bit of history: Five years ago, guest divers spotted the first lionfish in the marine park. DOE spent several days locating that one small, elusive fish before finally capturing it. Many more lionfish soon appeared, at first smallish adults and fry riding in on currents, eventually mature resident pairs, breeding and thriving.

Before spearing was sanctioned, dive masters and DOE live-captured lionfish for stomach content analysis by researchers at CCMI, the marine station on Little Cayman. Voracious feeders with incredible growth rates, lionfish were gobbling up the juvenile and feeder fishes in their territories at terrifying rates. (For further information, REEF, a non-profit organization begun by Paul Humann, the author of the familiar marine creature identification books, has also done important work investigating and educating on lionfish impact throughout the Caribbean.)

Eventually the government permitted licensed spearing in the park and the Wednesday night ritual hunt began. In addition to directly reducing the numbers, the hope was that it would buy time for the reef’s top predators, the Nassau groupers and reef sharks, to learn to hunt the lionfish on their own.

To that end, spearers at first offered them dead, then later wounded, lionfish. The spines pack a powerful punch to humans, adding a further degree of difficulty to the cull. But the groupers and sharks happily wolfed down the offerings without any ill effects.

It didn’t take long for the groupers to figure out divers in the water meant a free meal. They even took to pointing out to divers where the lionfish hid, like retrievers. Yet they showed little inclination or ability to take lionfish on their own. Recently, though, groupers, with a little encouragement, seemed to have figured out a hunting strategy, a cause for guarded optimism. (Little Cayman is home to one of the Caribbean’s last breeding populations of Nassau groupers. Groupers are nuclear hunters; they work together with one another as well as morays and nurse sharks, and if they figure this out, natural predation may well spare the Cayman reefs the decimation other islands are experiencing.)

While the groupers pose no threat to divers, the reef sharks, a generally benign bunch usually seen at a distance, have become overly curious, sometimes alarmingly so when spearing occurs.

Thus, for these brave volunteers, it’s not simply one more dive, tired and chilled though they may be after a long work day in the water. It’s not only the risk of puncture from venomous lionfish spines, it’s also roiled-up sharks they have to keep an eye out for. But their efforts are clearly paying off — appreciably fewer lionfish are in the park, the numbers on the cull are down, and the native fish populations are on the rebound.

At the end of the day, it’s the dogged efforts of these volunteers (and the DOE staff and some smart groupers) that might just save our beloved reefs.

So next Wednesday, as the sun sets and the dive masters trudge down the dock for the cull, we’ll be watching, with gratitude.

To all these unsung heroes of the reef, thank you.

1 COMMENT

  1. To the author.
    Thank you for the kind words of encouragement.
    We have certainly had great successes since 2008, however the cull intensity must be maintained to be effective.
    Two vital papers have been published by UF and CCMI relating to the work in LC.
    Frazer et al 2012 – Coping with the Lionfish Invasion – Can targeted removals yield beneficial effects? as well as Diller et al 2014 – Coping with the Lionfish Invasion – Evidence that naive, native predators can learn to help.
    These papers look specifically at the successes of managed population control and the possibility of local predators becoming biocontrol. (Both can be googled)
    HOWEVER – please note that the Little Cayman Community Cull has NEVER sanctioned the feeding of sharks. We actively promote this as a dangerous activity.