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.
Robertson, A., Garcia, A. C., Quintana, H. A. F., Smith, T. B., II, B. F. C., Gulli, J. A., ... & Plakas, S. M. (2013). Invasive Lionfish (Pterois volitans): A Potential Human Health Threat for Ciguatera Fish Poisoning in Tropical Waters.Marine drugs, 12(1), 88-97.
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Lionfish are notoriously generalist with their prey. This may make them a good model for stomach analyses to identify the trophic routes by which ciguatoxin moves through ecosystems.
ReplyDeleteThere was a huge campaign by the National Oceanic and Atmospheric Association (NOAA) encouraging America and the Caribbean to eat lionfish as a way of slowing their invasion. Such a strategy could only be harmful to human health, unless we had better understanding of ciguatoxin's ecological dynamics, such as how it relates to dinoflagellate blooms or specific marine communities.
Being dietary generalists would allow the association between specific prey species and ciguatera prevalence to be tested, yes, though I think they do already have a good knowledge of which low trophic level fish are responsible for ciguatera transfer. I am surprised the NOAA have given such advice, perhaps the findings of this study will change that, at least in regions where ciguatera is prevalent. Eventually the local folklore will incorporate lionfish, as it warns against the hazards of consuming other species at certain times of year or at certain sizes.
DeleteWere the fish tested all of equal size/age? As this is a problem of bioaccumulation people could be encouraged to eat the juveniles or if there is a specific size where CTX exceeds 0.1 μg/kg. It does seem like the best way to deal with an invasive species would be to make them a delicacy so I understand where NOAA are coming from.
ReplyDeleteYeah I remember Colin saying that with some other species people know not to eat them once they reach a certain size, as lionfish are invasive and so relatively new they haven't learnt this from experience yet, though I'm sure they'll learn fast.
DeleteIn this study they used only lionfish 'yielding sufficient flesh to be representative of an edible portion' (>50g). They used a large range, 50-600g. They predicted CTX level would increase with size, they did actually test it though and found there was no correlation, oddly.