Appetite for Extinction – Invasive Lionfish of the Bermuda – Robert S. Zuill (2013)

Lionfish are popular aquarium fish native to the Indo-Pacific region. The lionfish invasion in the western Atlantic began in the mid 1980s off the southern coast of Florida, USA. From Florida, lionfish have spread in all possible directions. By 2000, individuals had been sighted off the coast of North Carolina and Bermuda. First lionfish were reported from the Bahamas in 2004, where they quickly dispersed throughout the archipelago by 2007. The range of lionfish has increased further southward. Lionfish now occurs across a huge range from Rhode Island in the North to Venezuela in the south. This short documentary is one of the few to raise awareness to this ecological problem.

While two species of lionfish (Family: Scorpaenidae) have been found off of the eastern US (Red lionfish – Pteroides volitans and Common lionfish Pteroides miles), only P. volitans has been found in the Caribbean and Bahamas. In the Mediterranean a similar story may be brewing since Pteroides miles have also been sighted in Lebanon and Cyprus.

Results of field surveys along the U.S. Southeast coast and the Bahamas suggest that lionfish densities are similar or greater than most native grouper species (Serranidae). In some locations densities of P. volutans are reported to be more than eight times higher than densities reported from the lionfish’s native range.

Lionfish will have catastrophic consequences for marine life in the Carribean including already vanishing coral reef ecosystems. Once reproductively mature, they breed incredibly fast capable of reproducing every 55 days and during all seasons producing over a million eggs a year. During the mating period male lionfish will aggressively attack other males who attempt to invade their territories.

Lionfish have an unusual feeding behavior that appears to confuse many native Atlantic species and allows for efficient capture of small fishes. As they slowly approach their prey, lionfish produce a jet of water that is directed towards the smaller fish. This causes the fish to turn toward the predator, into the direction of the water flow, which may make it easier for the lionfish to swallow it. They eat anything that will fit down their mouths, wiping out entire populations of juvenile reef fish wherever they go. They are nocturnal predators and compete with top predators such as sharks.

Appetite of lionfish is a concern because a single lionfish can consume dozens of juvenile fish every day. Among those that fall prey is the social wrasse (Halichoeres socialis) which is an endemic reef fish to Belize. Social wrasse was discovered very recently. Extinction of social wrasse may trigger a chain of events that would negatively influence the tropical reef habitat. Most reef inhabitants feed on animals and plants found on the reef itself. The social wrasse almost act like the sponges. They feed on zooplankton in the water column. By doing so and they broaden the base of nutrients for animals higher up the food chain in the reef. This is very important in clear nutrient poor tropical waters. Absence of the social wrasse can narrow the resources. Wrasses form a significant functional group in every reef system and have evolved quite diverse survival behaviors including third party punishment.

Although lionfish are solitary predators and may live alone for the majority of their lives, they also display social behavior and have been observed to shelter together especially when they are juveniles and during spawning. During the day, they often retreat to ledges and crevices among the rocks and corals. They will fiercely defend their home ranges from other lionfish and other species of fish.

There’s one predator of lionfish reported from the Red Sea. The blue-spotted cornet fish has been reported to contain juvenile lionfishes in it’s gut content. Blue-spotted cornet fish also has migrated to the Mediterranean through Suez Canal pretty much the same way Pteroides miles did and is suspected to be one of the predators keeping lionfish population under control in the Mediterranean. Groupers in the Caribbean have been seen eating injured and dead lionfish speared by divers, but as yet they don’t appear to be active predators.

Lionfish are generally found at depths of 100 to 330 feet (30–100 meters). Juvenile lionfish may be found in shallow, nearshore habitats. Adult fish tend to be at deeper reef sites. Lionfish have been found in water as shallow as 3 feet (1 meter). In August 2010, a private submarine diving off the Bahamas filmed a lionfish in 1000 feet of water. In the Caribbean, lionfish have been found in a variety of habitats, including seagrass beds, mangroves, patch reefs and deep reefs. Their venomous spines keep predators away and the population numbers are increasing unchecked.

How does this poor swimmer fish disperse so effectively all over the Carribean in less than a decade? The origin of the lionfish invasion in the Bahamas has been a curious matter. Even though the Bahamas is very close to Florida, there appears to be a barrier for most reef species in between. A genetic investigation using the mitochondrial DNA from specimens collected across the Bahamas, North Carolina, and two sites within their native range (Indonesia and the Philippines) showed no significant differentiation between the Bahamas and North Carolina specimens (see the genetic relatedness tree constructed from this data below). This genetic study also confirmed the presence of only Pterois volitans (no Pterois miles were detected in the genetic analysis). The source of the Bahamian lionfish is egg and larval dispersal from the United States east coast population. The delay in arrival of lionfish is indeed due to a barrier between the Bahamas and east coast of Florida making it rather difficult for reef fish to move.

One way to protect reef communities is to spear them. There are many volunteer organizations who spear and collect lionfish on a regular basis. The smell of speared fish can attract and instigate a feeding behavior as this interesting footage captured:

Some restaurants are now including this fish on the menu. Once the poisonous spines are removed lionfish become edible.

Biological invasions are causing problems globally in terrestrial, freshwater, and marine ecosystems and there’s even a dedicated scientific journal publishing work done on invasive species. Ecologists are working to understand dispersal, colonization and proliferation of invasive species and advise legislators, economists and managers on how to tackle problems they cause.

 

5 Comments

  1. It is stated in the above discussion that only P. volitans is found in the Caribbean and Bermuda. I believe that this is just a mix up and it should say that only P. volitans is found in the Caribbean and The Bahamas. Both P. volitans and P. miles are found in Bermuda. The story might actually be more complicated than this and hopefully more detailed genetic analyses by other researchers will bring this to light.

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