In the last few months individual lionfish (Pterois volitans) have been spotted in and around the dive sites of Grand Cayman. First spotted in Little Cayman, in March 2008, since then a multitude of reports have come in.
A Lionfish captured at Eden Rock dive site. Grand Cayman. (Chris Burrowswood)
They may look pretty but in actual fact their presence on here on our reefs could mean the total devastation of the reef fish populations over a very short period of time. In fact in the Bahamas the lionfish reduced the number of native fish by 79% over a 5 week period[1]. These fish have voracious appetites, picking juvenile fish at will that have not evolved any natural survival instincts against them. In many areas it is thought that the whole coral reef community may be decimated as a result of lionfish predation.
Photo of invasive and non invasive areas (taken from Florida Museum of natural History website).
Lionfish are native of the Red Sea and Indo – Pacific regions. This covers most of Western Australia, New Zealand, Malaysia, Japan and throughout Micronesia.
Photo of invasive areas
(ref NOAA)
The first documented sight of lionfish on this side of the Atlantic was in Florida in the late 1990s, but since then they have spread rapidly down the eastern sea board and are now been caught as far as Haiti and Puerto Rica.
Lionfish like to be in warm marine tropical waters like 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. It could be either coral reef, or hard pan. The author has also seen them around and in wrecks. They tend to like overhead areas like caves, so you have to look up rather than down !. Lionfish hide in crevices during the night, coming out to hunt in the morning.
Lionfish are conspicuous predators, slow moving, they seem to glide along the reef without a care. Like “boys in the hood” The spines are not used for killing but for cornering their prey. The bright colours; dorsal, anal and pectoral spines ward off potential predators, and as a consequence they tend to be the top fish in the food chain, indeed even the nurse sharks don’t like them and spit them out when they have been fed them.
Lionfish had thought to be brought into Caribbean waters in the ballast of cargo ships however; studies have shown this to be erroneous. It is now known that most of the lionfish in our waters now came from just 8 fish (1 male and 7 females!) that were accidentally released in Biscayne Bay, Florida when an private aquarium broke during Hurricane Andrew in 1992. However since then 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 has remained in balance for hundreds of years with the lionfish a part of it. 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, the bottom line is that these fish reach sexual maturity very quickly and breed all year around. The female release two egg masses that are then fertilized by the male. These float rise to the surface when, after a few days the larvae become free floating. The larval stage lasts between 25 to 40 days, enough time for them to reach far on the Yucatan and Caribbean currents [2]
In order to control and manage the invasion a culling program has been introduced here 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 had been tried but the most effective way is by using two nets and then, carefully grabbing the body using spine resistant gloves, and putting them into a clear dry bag. (see photo)
The lionfish are then collected by the DOE, the gill filaments are removed for DNA testing and their biological data collected.
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 people who attended the talk as local marine laws prohibit the taking of any marine organisms from protected waters.
These programs represent the front line in the defense against invasive species and the work of organizations such as REEF have been incremental in finding; not just lionfish but other invasive fish around the world.
At the time of writing this article some 60 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 not seen lurking in cracks and crevices ready to ambush defenseless species of fish that have never seen the like of these in their existence. They have no chance, adaptation and evolution takes hundreds of years and by then it will be too late for this population. All we can do is, like King Canute, try and hold back the tide.
Acknowledgements
Photos : Chris Burrowswood
NOAA
Bradley Johnson, Department of the Environment. Cayman Islands
REEF
[1] Albins MA, Hixon MA. (2008) Invasive Indo – Pacific lionfish Pterois volitans reduce recruitment of Atlantci 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.
