In recent years the Indo-Pacific lionfish has spread from the SE coast of the USA throughout the Bahamas and Caribbean as far north as Bermuda and as far south as Venezuela. They can reduce the populations of native fish species very rapidly particularly by preying upon juveniles and reducing recruitment of all species to the reef habitat.
There are several examples of humans causing the substantial invasion of a (non native) species that thrives extremely well in its new habitat. In short order, this species explodes in biomass because of the lack of natural predators in that new environment and a food source that does recognize the invader as a predator. But none have had the dramatic (possibly immeasurable) damaging effect that the lionfish has had on Caribbean and western Atlantic native fish populations.
In response to the invasion of lionfish around the reefs of the Cayman Islands the Department of Environment now offers lionfish culling courses and licenses the use of Hawaiian slings to assist in capture and killing these fish. Being a small country with a low population but many of whom dive, fish or both, the culling of lionfish has become a weekly operation. Many restaurants are now offering lionfish on their menus.
Several dive companies have one day per week set aside for hunting lionfish, particularly in Little Cayman, the diving crown jewel of these islands. A study on the effectiveness of this culling is being undertaken by the Central Caribbean Marine Institute, (CCMI) which is based on the north side of Little Cayman. Following the Wednesday culling dives, researchers are measuring the catch per unit effort needed to make a dent in the population and cover the 3 mile stretch of wall at Bloody Bay to determine how fast new lionfish colonize the vacated areas. They are also assessing whether the structure and balance of Bloody Bay’s native fish population is affected by the continuing targeted removal of lionfish.
The targeted removal of lionfish has several benefits. Firstly, they are good to eat, so in spearing lionfish rather than grouper, snapper or hogfish, this removes some fishing pressure on the more popular reef species and will help reduce the mortality of juvenile reef fish caused by the invasive lionfish. The removal of significant numbers of larger lionfish means that those remaining are unable to prey upon larger individuals of the resident native fish populations.
Perhaps the best way to get people involved is to hold a lionfish culling tournament. There is the educational component when you register for the event, then the challenge of getting the most, the biggest (or smallest) and the creation of a tournament atmosphere while relieving the reefs of a very dangerous predator.
In a meeting with the Minister of the Environment last week, I learned of the plan to have a specialized task force assigned to culling lionfish around the Cayman Islands. I agree with this move. The threat to the coral reef habitat is so great that there needs to be radical action taken. The individual dive operators should not have to do the all grunt work on their own. After all, the dive business in the Cayman Islands is the focal point of the tourism sector.
Little Cayman also has the largest remaining population of Nassau groupers. This species, which is a favourite of divers and is the iconic Caribbean reef predator, may now have a new role in reef fish population restoration. Nassau groupers routinely follow divers and will consume lionfish speared by divers. Some divers say that Nassau groupers lead them to lionfish a bit like trained hunting dogs. For decades the Nassau groupers were traditionally fished heavily by artisanal fishermen at their spawning sites (locally called “grouper holes”) over the winter full moons. The Marine Conservation Board here protected these sites from 2003, and has just renewed that protection for another eight years. Good job! The Nassau grouper might be the knight in shining armour for reef fish populations. If this grouper, along with other large groupers and mutton snappers, can learn to attack and consume lionfish without the aid of divers then natural controls will begin to take effect in reducing lionfish biomass. After all, in the western Pacific and Indian Ocean, lionfish populations are maintained at equilibrium by their natural predators such as large groupers, jacks and the white tip reef shark.
— Guy Harvey
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