11. Jun, 2016

To kill a lionfish

In the Red Sea  lionfish  species such as  Pterois volitans, Pterois miles  and Pterois radiata are  one the most popular subjects for the beginning underwater photographer. They can make beautiful shots, with suitable lighting and some branches of soft coral as a colorful background.  The lionfish is not shy and  easy to approach, it  may turn towards the invader spreading its beautiful  pectoral fins making it look even more impressive. Lionfish species are native to the Indo-Pacific, but are now established along the southeast coast of the U.S., the Caribbean, and in parts of the Gulf of Mexico. One speculates that this all might have started  with retired aquarium enthusiasts releasing them in  Florida waters.*

Since lionfish are not native to the Atlantic, they have very few predators which caused  their number to increase dramatically, especially through the South Florida Estuaries, the Gulf of Mexico and the Caribbean Sea. A lionfish can eat enormous  quantities of juvenile fish:  an estimation is that  a single lionfish can reduce juvenile fish populations by 79% in just 5 weeks.  They also reproduce rapidly, spawning  every 4 days year-round and producing around two million buoyant gelatinous eggs per year. In the Indo-Pacific Oceans were lionfish are native, groupers, sharks and coronet fishes are known to prey on lionfish. In the Atlantic however, groupers are severely overfished and struggling to fill this role. Their growth  in Caribbean  waters is therefore difficult to control. 

NOAA researchers have concluded that invasive lionfish populations will continue to grow and cannot be eliminated using conventional methods. Marine invaders are nearly impossible to eradicate once established. One currently used  method is based on the principle ‘Eat Em to Beat Em’.  So on some islands the hunt of the lionfish is encouraged and licensed.  At the  island of Bonaire Scuba divers can follow a crash course in effective harpooning of the  lionfish, and PADI has developed a  “Lion hunter’ certificate to stimulate the hunt. It’s even possible to eat your catch called ‘Lionfish burgers’ afterwards in special beach BBQs.  Eating lionfish is considered be the "ultimate in guilt-free eating - delicious, nutritious and eco-conscious".**

But likely these hunting & eating practices are impractical and probably unsuccessful. So the only solution might be to let nature take care of itself, and hope that on the  longer term the disturbed fish population will restore itself.  Calling the lionfish invasion  the 'greatest threat of our century' may be pushing  the argument a bit to far ****.  Such a statement seems more  appropriate for the massive pollution and overfishing of our oceans. That COULD be one of the factors underlying this sudden invasion of Pterois.  In areas were sharks are abundant such as the Bahamas and Honduras, sharks may switch to a different menu, and start eating the lionfish, even when it comes second to their favorite natural dish. For instance if the lionfish are outnumbering the native species in their territories.  In Roatan Marine Park of the coast of  Honduras divemasters are now  even training sharks to hunt lionfish, with moderate success.***  Finally, a comeback of other large predators like the Nassau and Goliath groupers in the Western Atlantic could also help to bring the lionfish population down to acceptable proportions. 

Lionfish invasion  in the Mediterranean?

Mediterranean seawater temperatures are steadily increasing, and alien species are spreading, causing community shifts and tropicalization. Alien species have mainly  invaded the eastern basin of the Mediterranean, probably through the Suez canal.****  Recent enlargement of the canal coupled with sea surface warming is raising concerns that this problem will get worse. Examples of some alien species are the pufferfish (Lagocephalus sceleratus) and the Lionfish (Pterois Miles). P. miles was first recorded in 1991 off Israel, but recently seems to have  now colonised almost the entire south eastern coast of Cyprus in a period of only one year. Both species feed on local species in the Meditarranean taking advantage of their naiveté, and may threathen its biodiversity in the coming years. The pufferfish eats the economically  important  Sepia officinalis and Octopus vulgaris.  One hopes that native groupers such as Epinephelus marginatus will learn to prey on lionfish and control their invasion.

 

Useful links:

*http://sailorsforthesea.org/programs/ocean-watch/lionfish-invasion

**http://www.npr.org/sections/parallels/2014/11/10/361155911/why-divers-in-bonaire-are-so-eager-to-kill-the-beautiful-lionfish

***http://news.nationalgeographic.com/news/2011/03/pictures/110404-sharks-lionfish-alien-fish-invasive-species-science/

****http://lionfish.gcfi.org/index.php

****http://mbr.biomedcentral.com/articles/10.1186/s41200-016-0065-y