Lionfish (Pterois volitans and P. miles) populations have drastically exploded in the western Atlantic and the Caribbean in the past decade, and not without attracting some attention. The trouble is that these gorgeous fish sporting an array of venomous spines are invasive species. They naturally occur in the Indo-Pacific but have been introduced to Florida via aquarium releases and are now potentially causing significant changes to marine ecosystems, the inhabitats of which have not evolved with this fish. They can now be found from Costa Rica and Venezuela up the US eastern seaboard to Rhode Island, a truly impressive extent considering the first individual was found offshore of Florida in 1985. Recently, I was fortunate enough to dive in Roatan, Honduras on my honeymoon and lionfish were a relatively common sight, despite their efforts to hide among the barrel sponges on the benthos. They could potentially spread well into the southern hemisphere, along the the coast of South America, based on the lethal minimum water temperature [pdf] for this fish (10 C). Lionfish feed upon the larvae of reef fishes, undercutting the next generation of fishes. They can spawn year-round and release buoyant egg masses that can float in the currents for weeks, ensuring a wide distribution.
The complete removal of these fish is unlikely, though decreases in abundances in small areas could be seen with intense fishing effort. Lionfish have been found in the bellies of groupers in the Caribbean. Groupers indeed seem to function as a biocontrol, with lionfish numbers decreasing when grouper numbers are high. However, this only would be the case in areas with large grouper populations, and sadly these areas are so chronically overfished that this is not a tenable solution.
All signs point to lionfish remaining abundant in their newfound neck of the ocean for the foreseeable future, so why not at least get some use out of them? We’ve shown a remarkable ability for unsustainable, chronic overfishing in general, so why not use this usually unfortunate skill and eat them? However, lionfish (as well as grouper), can accumulate ciguatoxin, which can cause problems for humans, so this is not an option where this toxin is found.
Dr Ricardo Betancur-R. and colleagues in a recent paper published in the Journal of Biogeography thought to use their successful invasion and expansion to test theories of how marine organisms are connected throughout the Caribbean and the western Atlantic. Using genetic methods and tissue samples of lionfish, the researchers analysed mitochrondrial DNA and analysed their data with previous work from lionfish in both an invasive context and within their home range. Genetic diversity was much higher for both species of lionfish within their native ranges than their non-native stomping grounds (1 versus 38 haplotypes for P. miles, and 9 versus 36 haplotypes for P. volitans). This reduction in genetic diversity, in this case caused by a founder effect, lends strong evidence for a single introduction and dispersing out, rather than multiple independent introductions. Even with reduced genetic diversity, clear differentiation as seen between northern populations of P. volitans and the those in the Caribbean. Interestingly, P. miles appears to be limited to the northern areas samples (North Carolina and Bermuda) while P. volitans occurs throughout the western Atlantic and the Caribbean.
This introduction is believed to be caused by aquaria releases. Yet this event was not associated with Hurricane Andrew, a popular myth that the authors seek to dispel. The idea is that the storm caused 6 individuals to escape from a aquarium in Florida. The storm, which occurred in 1992, postdates the first lionfish seen in the region by seven years. Additionally, the researchers calculate that the minimum number of founding individuals to explain the current diversity would have be at least eight.
Using both the known chronological progression of the invasion and genetic data, these scientists tested multiple hypotheses concerning how connected the Caribbean is, both within itself, and with the western Atlantic. You see, the ocean is not a uniform environment, even in surface waters. Dispersal barriers can exist in the form of circulation patterns or other environmental barriers. In the Caribbean, many of these phylogeographic breaks are thought to exist, and thus explain some of the differences in marine fauna throughout the region. This study mostly validated these potential connections. For example, previous work supported the idea that the US east coast and Bermuda are well-connected via circulation patterns. Both the chronology of the invasion (lionfish showing up in both placed simultaneously) and the genetics showing no differentiation between the populations provide strong evidence for this. Support for a biogeographical break between the US and the Bahamas is also present, and suggests that the western/southern Caribbean (Columbia – Panama) is not as isolated as the eastern Caribbean, contrary to earlier thinking.
Invasives are reshaping ecosystems, either by human introductions, like the lionfish, or by a changing climate creating opportunities for species to move in. In this case, lionfish are likely here to stay, at least in some capacity, so we might as well use them to further our knowledge about how the ocean is organized.
Live on the coast? Check out a lionfish cookbook here.
Edit: 16 August, After a reader pointed out (correctly, it appears) that in some areas lionfish can carry the ciguatoxin (along with other high-trophic level fish that we eat), this post has been amended slightly.
Barbour AB, Allen MS, Frazer TK, & Sherman KD (2011). Evaluating the potential efficacy of invasive lionfish (Pterois volitans) removals. PloS one, 6 (5) PMID: 21572951
Betancur-R., R., Hines, A., Acero P., A., Ortí, G., Wilbur, A., & Freshwater, D. (2011). Reconstructing the lionfish invasion: insights into Greater Caribbean biogeography Journal of Biogeography, 38 (7), 1281-1293 DOI: 10.1111/j.1365-2699.2011.02496.x
Mumby PJ, Harborne AR, & Brumbaugh DR (2011). Grouper as a natural biocontrol of invasive lionfish. PloS one, 6 (6) PMID: 21731769