Lionfish are native to the Indian Ocean, South Pacific and Red Sea, however, following their introduction into Florida waters in the 1990s they have rapidly spread across the northwestern Atlantic and Caribbean. They have spread so successfully due to a lack of natural predators, high reproductive rates and high growth rates.
This study focuses on the presence of lionfish in the U.S. Virgin Islands in the Caribbean, where lionfish were first reported in 2008. Their sudden abundance has caused dramatic ecological shifts as they outcompete native species of reef fish for resources. In an effort to reduce their numbers, they have become targeted by fisherman, and whilst this provides an economic opportunity for local communities, it may also pose a risk to human health if lion fish act as a vector for Ciguatera Fish Poisoning (CFP).
A brief description of ciguatera: there are 500,000 new cases of CFP annually, it is caused by consumption of reef fish that have accumulated the precursors to ciguatoxins (CTX) produced by dinoflagellates. Symptoms can be gastrointestinal, neurological or cardiovascular. Chronic symptoms that last for years are reported in 20% of cases, acute symptoms are the result of CTX binding to cell membrane sodium channel and keeping them open, depolarising the cell, which can lead to cell death.
The risk of contracting CFP is minimised by local knowledge of which fish are hazardous and should be avoided in certain harvest areas. However, because lionfish are an invasive species and a recent addition to Caribbean fisheries, the level of risk they pose has not yet been established. Potential cases of CFP linked to consumption of lionfish instigated this study.
Lionfish were collected from waters around the U.S. Virgin Islands, and area described as ‘hyperendemic’ for CFP. Samples were tested used in a Neuroblastoma Cytotoxicity Assay, which tests for sodium channel toxins. All positive samples were concentrated and analysed by liquid chromatography and mass spectrometry to positively identify CTX.
Of the 153 lionfish tested, CTX presence tested positive in 40% of fish. 12% contained a level of CTX higher than the FDA ‘guidance level ‘of 0.1 μg/kg. The average level of CTX in fish above this level was 0.2 μg/kg. These rates are similar to those seen in other predatory reef fish that are currently avoided by local fisheries. Individual lionfish apparently consume an estimated 50,000 reef fish per year, fish from lower trophic levels that are an important step in the conversion of dinoflagellate- produced precursors to CTX, so bioaccumulation is to be expected.
This study it the first to document that lionfish are a vector of CTX in endemic regions. They have highlighted a potentially hazardous fish species that is currently fished and consumed in regions that have learnt to avoid other CFP-associated species. The novelty of the fish due to its invasive nature has led to local knowledge playing catch-up. However, with this sound evidence of the CFP risk, hopefully now communities will learn to avoid consumption of lionfish in CFP endemic regions.