The Caribbean War against Lionfish


This week, Anjani Ganase, marine biologist, tells us what we need to know about the presence of lionfish on Caribbean reefs. With no natural predators in the Atlantic, lionfish feed voraciously upon juvenile fish that are essential to healthy coral reefs. Introduced carelessly in Atlantic waters, man must take on the responsibility to stem the invasion.
This article was first published in the Tobago Newsday on Thursday, November 10, 2016.
Follow Anjani on twitter @AnjGanase
 
Lionfish in its native home, the Great Barrier Reef. Photo by Richard Vevers, The Ocean Agency, XL Catlin Seaview Survey 2012.
Lionfish Invasion
Naturally present in the Indo-Pacific tropical waters, the lionfish is a common ornamental fish in the aquarium trade. In the 1980s, two species of lionfish - red lionfish (Pterois volitans) and the devil firefish (Pterois miles) the less common of the two - were introduced into the marine waters along Florida’s east coast, a notorious “hotspot” for marine introductions. Lionfish is one of over 30 introduced marine species off the coast of Florida. By the 1990s they expanded their range farther along the east coast with sightings as far north as New York. Fifteen years later, in 2005, there were regular sightings in Bermuda and Bahamas and parts of the Gulf of Mexico. After this, the invasion of lionfish to the rest of the Caribbean accelerated. Lionfish continued to expand southward into the western Caribbean, invading the Greater Antilles, Cuba and Hispaniola, Belize and Mexico and parts of the Central America. By 2010, the invasion continued into the islands of the Netherlands Antilles west of Trinidad and Tobago, and the Lesser Antilles, St. Maarten and Guadeloupe to our northeast. By 2011, Barbados spotted their first lionfish so its southward track was inevitable, and Tobago had its first confirmed sighting in 2012. Although lionfish have invaded most of the Caribbean, experts don’t expect that they would be stopping here. Considering their environmental range, they predict that they will continue to spread further south along the coast of South America, to Guyana, French Guinea and eventually to Brazil inhibited only by colder waters. However, with warming climates they might even expand further.

Lionfish Strategy
In their native habitats, lionfish are uncommon and relatively unknown. On the Great Barrier Reef, an encounter with a lionfish was one to check off; but sighting these got old pretty quickly when they saturated your reef view. Lionfish are relatively rare in their native region in the Indo-Pacific; and they’re generally not considered a preferred meal because of their venomous spines. Adults are hardly considered prey, except by Cornetfish in the Indo-Pacific and Nassau Groupers in the Bahamas.

On the other hand, lionfish are incredible hunters. In one study that compared the hunting strategies and prey choices of lionfish in the native and introduced territories, they are generalist feeders, feeding typically on juvenile and small fish species. Their banded coloration helps them to blend in while hunting. They mostly hunt in low light, at dawn and dusk or overcast conditions, which is common for most predators including sharks. During daylight, they hide in cryptic environments such as under rocky crevices. They have two main strategies for hunting. They fan out their pectoral fins - similar to how batman fans out his cape before he descends on the bad-guys – to herd and corner small fish. Lionfish also have a blowing strategy where they propel water onto the prey to confuse and disorient them. Although it was found that the techniques and feeding times did not change much between the regions, it seems that the success rate is higher in the Caribbean because they are not perceived as a threat. In the Caribbean, they have been able to feed on larger fish. The blowing technique also seems to be unnecessary, as prey is more easily caught. Pacific fish species seem to be more aware of their presence.

The broad range of tolerance to different environments, occurring across significant temperature and depth ranges, has facilitated lionfish presence in the Caribbean. Lionfish can be found down to 100 m deep. They also mature quickly, have fast reproductive rates and long life spans.

Ecological Impacts
What lionfish feed on is the main cause for concern in the Caribbean. One group of fish – the parrotfish – are important grazers of macro-algae on Caribbean reefs and crucial in maintaining low cover of algae, which are the main competitors against hard corals for space.  Lionfish can feed heavily on the juvenile populations of these crucial herbivores; and on coral reefs where populations of parrotfish are already severely compromised the impacts can be disastrous for the health of our coral reefs. They also undermine the predator population by feeding on the already heavily depleted juvenile populations of groupers and snappers, reducing their recruitment levels on coral reefs, even as they compete with them for food.

What eats Lionfish
Island states have taken up the responsibility of hunting and killing lionfish in an effort to limit their populations at least within the diving limits in shallow coral reef environments. Special tools were made: a polespear and a canister were designed to kill lionfish safely while minimising damage to the reef and other marine life. The spears have to be used in close range with the lionfish. At this time, lionfish seem to be unaware of humans as a threat; but don’t miss, because they’re also quick learners. In the Bahamas and other countries throughout the Caribbean, lionfish tournaments have been organised in an attempt to cull their populations, while creating the opportunity to monitor lionfish size, numbers and distributions. Once enough are caught, the lionfish can be used in culinary competitions, and people can learn how to safely prep this fish for eating. There is a lionfish cookbook produced by REEF.org and is available on Amazon.


Invasive lionfish cruising in the daylight on the Belize Barrier Reef. How many can you see? Photo by XL Catlin Seaview Survey, Global Reef Record.

What can we do to restore balance in our marine ecosystems? The observations that Nassau Groupers were feeding on lionfish occurred within one of the best marine reserves in the Caribbean, where the grouper populations are in the top one percent compared to the rest of the Caribbean (Mumby et al. 2011). Unfortunately, groupers are delicious food fish for humans; and healthy grouper populations may be as unlikely as finding another readily available bio-control on lionfish.

Unless we drastically curb the high levels of overfishing occurring throughout the Caribbean by setting up marine protected areas and regulating fisheries, lionfish will continue to be a threat to our coral reefs. Properly managed marine protected areas offer the best solution to many of the problems of the marine environment, including a natural means of curbing lionfish. Protected coral reefs will be more resilient to ecological and human induced changes.

References:
Schofield , P. J., (2010), Update on geographic spread of invasive lionfishes (Pterois volitans [Linnaeus, 1758] and P. miles [Bennett, 1828]) in the Western North Atlantic Ocean, Caribbean Sea and Gulf of Mexico Aquatic Invasions (2010) Volume 5, Supplement 1: S117–S122
Mumby PJ, Harborne AR, Brumbaugh DR (2011) Grouper as a Natural Biocontrol of Invasive Lionfish. PLoS ONE 6(6): e21510. 

Cure, K. Benkwitt, C.E., Kindinger, T. L., Pickering, E. A., Pusack, T. J., McIlwain, J. L., Hixon, M. A. (2012) Comparative behavior of red lionfish Pterois volitans on native Pacific versus invaded Atlantic coral reefs, Marine Ecological Progress Series, Vol. 467: 181–192.
Morris, J.A., Jr., and P.E. Whitfield. 2009. Biology, Ecology, Control and Management of the Invasive Indo-Pacific Lionfish: An Updated Integrated Assessment. NOAA Technical Memorandum NOS NCCOS 99. 57 pp.


 



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