Tackling invading lionfish

The impact of carnivorous lionfish in Caribbean waters has been well documented, but by using different methods there may be a way to get lionfish under control.

Two visually identical species of lionfish were introduced into the Atlantic via the US aquarium trade in

the 1990s and have been sighted from Massachusetts on the East Coast of the US to South America, including the Gulf of Mexico, Bermuda, throughout the Bahamas and across the Caribbean.

Their expansion has been extremely rapid and exponential in scope and follows the flow of currents around the East Coast and Western Atlantic on into the Caribbean.

As has been well documented lionfish are generalist, indiscriminate carnivores that consume in excess of 56 species of fish and many invertebrate species.

They can also eat a lot: scientists have recorded up to 22 fish in a single lionfish stomach as these opportunistic predators feed a high metabolism, spurring their exceptional reproductive rate.

This type of aggressive feeding behaviour has knock-on effects and may impact multiple, trophic levels by reducing the abundance of other herbivorous fishes that keep seaweeds and macroalgae from overgrowing corals.

The overwhelming consensus among scientists is that lionfish eradication will be impossible due to the geographical extent of the invasion.

It is said lionfish have no natural predators in Caribbean and Atlantic waters. However, now that divers are licensed to cull lionfish, the resident dive masters on Little Cayman qualify as predators in every sense of the word, and they hunt in packs.

All the dive resorts are seriously committed to the reduction of the lionfish population in the world famous Bloody Bay Marine Park.

Teaming up each week, a different resort donates boat hours and all four resorts allow staff to attend.

The culls are organized by the Central Caribbean Marine Institute, who are also using this as a unique opportunity to collect data on the effectiveness of lionfish removal efforts.

Data of this type is desperately needed to build accurate models and plan for the future of lionfish population management.

Researchers on staff at the institute are analysing stomach contents, reproductive maturity, age and growth of the lionfish.

Similar data collected from other areas in the Caribbean suggests that this invasive population of lionfish is growing larger and faster than their Pacific cousins.

We hope that once the data from Little Cayman is analysed, it will provide scientists with more accurate information that will in turn help us to make better management decisions.

Another possible predator of the lionfish is the grouper, which has been trained by dive masters to eat and also hunt the lionfish. This project has been a surprising success.

Nassau groupers have been witnessed hunting the lionfish in the Bloody Bay Marine Park indicating that this important and threatened grouper species may be a critical part of nature’s own solution over time.

The high level of commitment from dive masters on Little Cayman can make a large difference in localized areas such as the Bloody Bay Marine Park.

The outpouring of support and community action in Little Cayman should be used as an example for other communities wishing to make a dent in their local batch of venomous invaders.

In addition to the lionfish culls, the institute also hosts appreciation barbecues for the participating dive masters using the lionfish caught on the hunts.

Lionfish meat is very palatable, which offers an extra incentive to continue the push to collect more fish.

All of the dive resorts and the institute recognize the importance of controlling the local lionfish population, even if operating costs increase due to extra boat time and man hours.

The weekly culls have become so popular that space on the dive boat is at a premium. The look on the latecomer’s faces as they loose their spot to an increasing waiting list is priceless.

With single catches reaching triple figures and with the added excitement of the hunt as well as the camaraderie around the bar afterwards, it’s easy to understand why the culls are so popular amongst the dive masters.

With the Little Cayman community this invested, they have an excellent opportunity to set the standard for the rest of the Caribbean with regard to controlling lionfish numbers.

Furthermore, besides the obvious positive impact on the environment, scientists and reef managers have a better opportunity to understand whether culling over a controlled area for an extended period of time can be successful, and possibly how much effort it will take to reduce the impact of this invasion.

These results may provide the impetus for a more regional effort in the future.