Hybrids of the deadly Japanese delicacy pufferfish linked to climate change

Pufferfish, or fugu, are a Japanese delicacy that can kill a person who ingests it within hours if it is not prepared properly. The Japanese have eaten fugu for thousands of years, and after it was outlawed by Toyotomi Hideyoshi, the samurai general who unified Japan in the 16th century, peasants continued to eat it in secret and died in multitudes. The ban on fugu was lifted after World War II following years of petitioning by fugu fans. Despite its deadly nature, the fish has an almost comical face and, with its puffed cheeks and open mouth, looks as though it’s perpetually surprised to be so sought after for special occasions.

A kilogram fetches as much as 30,000 yen at Japanese fish markets, and in the December holiday season a luxury fishmonger in Tokyo can sell up to USD $88,000 worth of the fugu on any given day. Earlier this year, a supermarket in western Japan accidentally sold five packets of fugu without its poisonous liver removed the town used its missile alert system to warn residents. Now, fishermen are discovering an unprecedented number of hybrid species in their catch as seas surrounding the archipelago, particularly off the northeastern coast, are experiencing some of the fastest rates of ocean warming in the world. With pufferfish heading north to seek cooler waters, sibling species of the fish have begun to inter-breed, triggering a sudden increase in the number of hybrid fish.

Of approximately fifty species of fugu around Japan, twenty-two of them are approved as edible by the government. Chefs and fish butchers handling pufferfish are specially trained and licensed to remove its liver and reproductive organs, which contain tetrodotoxin, a potent neurotoxin. Confusingly, the location of the deadly neurotoxin differs in certain types of pufferfish; it can sometimes be found in its skin or muscle, as well as its reproductive organs. Hybrids are as dangerous than regular fugu and difficult to distinguish from established species. To avoid accidental poisonings, Japan prohibits their sale and distribution, but with the rise of these unclassifiable hybrids, fishermen and fish traders are discarding a sizable share of their catch.

Associate professor at the National Fisheries University Hiroshi Takahashi first noticed the increase in hybrid pufferfish six years ago when he started receiving calls from a scientific facility on the northeastern coast of Japan’s main island that had buckets of fugu it couldn’t identify. In the fall of 2012, nearly 40 percent of fugu caught in the area were unidentifiable, compared to less than 1 percent studied previously. “It wasn’t one out of a thousand as it had been in the past; this was on a completely different scale,” he says. To an untrained eye, hybrids are barely discernible. Even veterans in the industry say it’s nearly impossible to tell apart “quarters,” or second-generation offspring of hybrid fish. At the end of June, more than 20 percent of pufferfish caught in a single day off the Pacific coast of Miyagi prefecture, 460 kilometers northeast of Tokyo, were hybrids.