An Invasion of Caribbean Waters
by Sharon Adam-Whitmore
Lionfish may look pretty but their non-native presence in the Caribbean could mean the total devastation of reef fish populations over a very short period of time. In the Bahamas lionfish reduced the recruitment of native fish by 79% over a five week period (1).
Their population is spreading. This year, 2009, lionfish (Pterois volitans) have been spotted in and around the dive sites of Grand Cayman. First seen in Little Cayman, in March 2008, since then a multitude of reports have come in.
Lionfish have voracious appetites, picking out juvenile fish that have not developed any natural survival instincts to avoid them. Whole coral reef communities may be decimated as a result of lionfish predation.
Lionfish are native to the Red Sea and Indo–Pacific regions. This covers most of Western Australia, New Zealand, Malaysia, Japan and Micronesia. (The map below documents the creature’s native regions (red dots) and those regions it has invaded (white dots).)
The first documented sight of lionfish on the Caribbean side of the Atlantic was in Florida in the late 1990s. Since then they have spread rapidly down the eastern sea board and are now being caught as far afield as Haiti and Puerto Rico.
Lionfish like to be in warm marine tropical waters such as the Red Sea. They have been found in depths of up to 400ft, but are usually seen from 80 to 200ft. They don’t mind what type of habitat they live in, whether coral reef or hard pan. They hide in crevices during the night and come out to hunt in the morning. I have seen them around wrecks and caves, often gravitating to overhead areas so that you often find them by looking up rather than down.
Lionfish are conspicuous predators, slow moving, gliding along the reef without a care. The spines are not used for killing but for cornering prey. Their bright colours and dorsal, anal and pectoral spines ward off potential predators. As a consequence they tend to be at the top of the food chain. Even the nurse sharks don’t like them and spit them out when they have been fed them.
It was thought that lionfish were brought into Caribbean waters in the ballast of cargo ships but studies have shown this to be erroneous. (The map above documents the present distribution of the – non-native – lionfish.) Genetic evidence of a strong founder effect indicates that most lionfish in Caribbean waters came from just eight fish (one male and seven females) that were accidentally released in Biscayne Bay, Florida when an private aquarium broke during Hurricane Andrew in 1992. Since that time it’s thought that other private aquarists have released fish into the water, probably by flushing them down the toilet.
So what can be done about this invasion? The answer is that we cannot possibly stop the lionfish now that they are in our waters. Scientists have had very little base line information to go on since there was never a problem in their native habitat, where the ecosystem including lionfish has remained in balance for hundreds of years. It’s only now that information is being gathered in order to understand the nature of these creatures.
The news is not good for the native fish. Lionfish reach sexual maturity quickly and breed all year around. The female releases two egg masses that are then fertilized by the male. These rise to the surface and after a few days the larvae become free floating. The larval stage lasts between 25 to 40 days, enough time for them to travel a long distance on the Yucatan and Caribbean currents (2). So lionfish breed faster, have more young than most other native fish, and are extremely robust as a species.
In order to control and manage the invasion, a culling programme has been introduced in Cayman as well as in Bermuda and the Bahamas. In Cayman the Department of the Environment (DOE) invited first local dive masters and later the general public to a presentation given by a NOAA/REEF/USGS representative. The talk was aimed at educating local dive operators and showing them the best, tried and tested, technique for capturing the lionfish. Spear fishing has been tried but the most effective way is to use two nets in a kind of pincer movement, drawing the fish into one of them. Then, whilst on a steady surface like sand or hardpan, the fish are transferred from the nets into a dry bag by carefully grabbing the body using spine resistant gloves. (See photo.)
The lionfish are then collected by the DOE, the gill filaments are removed for DNA testing and their biological data recorded.
There have been many workshops all around the Caribbean to facilitate early detection and a rapid response to this threat. Licenses have been issued to those divers who attended the talk as local marine laws prohibit the taking of any marine organisms from protected waters.
These programmes represent the front line in the defence against invasive species. The work of organizations such as REEF have been incremental in discovering not just lionfish in these waters but other invasive fish around the world.
At the time of writing this article, some sixty lionfish have been captured in Cayman waters and over a hundred have been reported.
However, as is often the case, for every one lionfish seen there are many lurking unseen in cracks and crevices ready to ambush defenceless species of fish that have never seen the like before. They have no chance. Adaptation and evolution takes thousands of years. Along with climate change, over-fishing and pollution, this invasion may be one more factor contributing to the death of the coral reef of the Cayman Islands.
All we can do, like King Canute, is try to hold back the tide.
(1) Albins MA, Hixon MA. (2008) Invasive Indo – Pacific lionfish Pterois volitans reduce recruitment of Atlantic coral-reef fishes. Mar Ecol Prog Ser Vol 367:233.
(2) Morris et al (2008) Biology and Ecology of the Invasive Lionfish, Pterois miles and Pterois volitans. Proceedings of the 61st Gulf and Caribbean Fisheries Institute. Nov 10-14.
2-6 May 2009
Bradley Johnson of the Department of the Environment, Cayman Islands;
Lad Atkins, REEF;
Stephanie Green, Simon Fraser University.
Getting stung by a lionfish
At the site of the injury the pain is accompanied by an intense throbbing which radiates out and reaches its full intensity after 60 to 90 minutes and lasts for 6 to 12 hours. It may persevere for days or weeks.
Lionfish do not inject the venom, (a neurotoxin) as a snake does. The spines, which have a sheath around them, are situated near venom glands which secrete the toxin into the grooves of the spine. The toxin enters the puncture wound made by either the dorsal, pelvic or anal spines.
Severity of the pain can differ amongst individuals and individual lionfish. Alan Ladd of REEF tells the story of a local fisherman who reckoned he was becoming “immune” after having been stung a few times, but even so he said that the pain was so intense that if he got stung again he’d want to get hold of a machete and cut his arm off!
Lionfish stings are best treated as soon as possible by placing the affected area in water as hot as one can stand and taking some painkillers, then seeking medical attention. Of course the best cure is prevention: if at all possible, look but don’t touch.