AN INVASIVE pufferfish is causing havoc for Mediterranean fishers, and the toxin it carries is turning up in native shellfish.
The silver-cheeked toadfish (Lagocephalus sceleratus, pictured) is native to the Pacific and Indian Oceans. It has thrived in the Mediterranean since arriving this century, apparently via the Suez Canal.
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It is a pufferfish, the group eaten as the delicacy fugu in Japan. Some of its organs contain tetrodotoxin, a lethal poison.
But so far its toxicity isn鈥檛 the main problem. Instead, the fish bite through fishing nets that cost thousands of pounds to get at the catch inside.
鈥淲e showed the fishermen photos of fish and we asked which one do you come across, and they identified [the pufferfish],鈥� says Vahdet 脺nal at Ege University in Turkey. 鈥淭hen we asked how much damage this species causes to their fishing gear.鈥�
脺nal has repeatedly surveyed hundreds of Turkish fishers. From 2011 to 2013, the losses reported by small-scale fisheries more than doubled, from about 鈧�2 million to 鈧�5 million. His latest unpublished data offers no respite. 鈥淭he problem is increasing,鈥� he says.
The EU鈥檚 BlueBRIDGE project is investigating how far the fish will spread. Its unpublished results suggest the population will rise further before levelling out. However, the species could establish itself in the western Black Sea: a key fishing area troubled by rising pollution.
However, 鈥渋t will not expand completely in the Black Sea because it seems to prefer quite hot waters,鈥� says team member Gianpaolo Coro at the Alessandro Faedo Institute of Information Science and Technology in Italy.
Toxicity could become a problem. Tetrodotoxin is turning up in Mediterranean species such as shellfish, as are the bacteria thought to make it for the pufferfish, says Chris Elliott at Queen鈥檚 University Belfast, UK. 鈥淲e鈥檙e pretty sure that pufferfish are the carrier,鈥� he says, but this hasn鈥檛 been conclusively shown.
The toxin is spreading. A 2015 survey of UK waters recorded it in molluscs. A follow-up published in 2017 found it was widespread in UK waters, including in edible species like mussels (Marine Drugs, ).
鈥淸Tetrodotoxin] is there in low amounts, it wouldn鈥檛 make people ill,鈥� says Elliott. 鈥淏ut we would say in about one, two or three years, this will be very serious and there could be fatalities.鈥�
There are few options for removing the pufferfish, says Bella Galil at Tel Aviv University in Israel. 鈥淲e are always closing the door after the horse has bolted.鈥�
However, the trick could be finding a use for tetrodotoxin. It may be useful for pain relief, for example during chemotherapy.
鈥淚f you can find a way to extract [the toxin], that would create a market for the fish and there would be more removals of it,鈥� says Demetris Kletou at Marine and Environment Research Lab in Cyprus.
This article appeared in print under the headline 鈥淚nvasion of the toxic pufferfish鈥�
