One of the many reasons I traveled to the Bahamas recently was to film an invasive species that is creating serious ecological problems in coral reef communities there. I'm referring to the red lionfish (Pterois volitans). This species is native to the warmer waters of the western Pacific Ocean and I have observed it there in its natural habitat. I will soon head to the Philippines to film it. However, it is out of place in the Caribbean and SW Atlantic.
I wanted to observe it in Bahamian waters to add another example of the impact of invasive species in environments where they are not native. My readers are well aware of the terrible infestation of the Asian seaweed Sargassum horneri that has infected our local kelp forests since 2006. When species from another region enter an area where they have no predators (or herbivores for the seaweed), they often proliferate and impact the natives.
In their place, these lionfish can be quite beautiful. They have very showy fin rays and are very colorful. However, don't venture too close as the fin rays carry a serious toxin that can cause an unwary diver (or predator) to perform a major "hurt dance." Lionfish are relatives of the scorpionfish we see in our waters as well as stonefish from other areas, all of which use employ toxins to protect them from harm.
The arrival of an invasive species often involves a substantial "leap" geographically. For example, the lionfish went from the Pacific to the Atlantic (and not via the Panama Canal) and the seaweed from Japan to Long Beach, California. It is rare that a species can make such a leap without a little help in the form of intentional or accidental human actions. The Asian alga impacting our kelp forests arrived in southern California via a commercial vessel from the Seto Inland Sea in Japan. On land about a third of Catalina's plant species are non-native, with some arriving from Europe, Africa, South America and Asia over the centuries.
I've stated that the red lionfish did not swim into the Caribbean via the Panama Canal (although some marine species have done so in both directions). Just how did it get to places like the Bahamas? In this situation humans are not entirely to blame. It is believed that Hurricane Andrew "released" six lionfish from an aquarium back in 1992. DNA studies have suggested the current infestation throughout the Caribbean, Gulf of Mexico and Atlantic had its roots in those few individuals although others have probably been added to the mix when aquarium enthusiasts released their own "pets."
How did lionfish spread so quickly? I've mentioned that they have no natural predators in their new surroundings. Another factor is that the local prey species have no inherent defense against these voracious munchers. The fact that a female lionfish may produce up to two million eggs a year certainly provides an answer to the puzzle as well! Prodigious reproduction is a key to many species... and you thought my emphasis on "munching" and "mating" was the product of an overly "fertile" mind!
This species is also found as far north as Rhode Island. Fortunately, at these northern limits of distribution the water is often too cold for reproduction, and in winter may prove deadly to them. In areas where their populations are at highest density, NOAA scientists report as many as 1,000 lionfish per acre!
The diet of the lionfish is generalized. It does not not focus on a few individual species for its food, but will gobble up just about anything it encounters. Kind of like the good "Doc" although I wonder if it, too, would turn down asparagus and peas (yuck). Because lionfish are not picky eaters, they have a virtual buffet of things to munch on around the reefs. I used to mortify my Mom when we'd go to an "all you can eat" buffet. Once she retired to the car while my grandfather egged me on! The lionfish has been observed swallowing up to 20 small fish in half an hour and they can even gobble up one that is more than half their size! At least I can't do that (well, not in a single sitting).
By doing so, lionfish significantly impact populations of the native fish on Caribbean reefs, including devouring the young of many species that have already been overfished commercially. This may limit breeding stock for the next generation. In addition, by gobbling up these prey species, they substantially reduce the food supply for native predators.
My dive trip on Blackbeard's had advertised an effort to control the lionfish on our cruise, but that didn't happen because the government was requiring new permits. I had looked forward to filming it. Initially, control efforts focused on spearing as many of these pests as possible. However, they may live down to depths of 400-500 ft, with the deeper water individuals soon replacing the ones removed from the shallower reefs. Many have turned to a method of control used by humans to wipe out many other species... catching them for food! I hear their light, flaky meat is rather tasty and many lionfish recipes are out there for you to try. Control in some areas may be possible, but total eradication of this invasive species is probably unfeasible. Just as the lion is known as the king of the beasts, the lionfish has now become the king of the Caribbean reefs.
© 2013 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!
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The voracious red lionfish in the Bahamas.
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Dr. Bill Bushing.
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