The star of a Japanese dish called fugu is a puffer fish that produces toxins so deadly that it can kill if prepared improperly. Yet the delicacy is so popular that overfishing may be pushing one species of puffer to the brink of extinction, according to a report by an environmental group. The Chinese puffer, Takifugu chinensis, is one of the top four puffer species used in the dish in Japan, according to the International Union for the Conservation of Nature.

Like most types of puffer, it ingests toxin-producing bacteria that it uses as a defense against predators in the wild. The fish stores these toxins in organs such as the liver — one fish can contain enough toxin to kill up to 30 people. The IUCN is not connected to a government and doesn't have any regulatory power, but maintains its Red List as a resource to inform people about species it believes are under siege. Japanese chefs typically train to prepare the fish safely, and often need to be licensed. But even with these precautions, accidents happen. In 2011, a two-Michelin-starred Tokyo restaurant served up some fugu that almost killed a diner.Nevertheless, the fish is prized in Japan and elsewhere for its subtle flavor, and often the dish does not come cheap. A meal at Tokyo's Tsukuji Yamamoto (two Michelin stars) averages about 35,000 yen — roughly $300.

SOCIAL

'If you're eating fugu and your lips turn numb, you're well on your way to being dead' http://t.co/hhMLN0lVZ9 pic.twitter.com/2rGxqk1KYU — Chicago Tribune (@chicagotribune) November 19, 2014

Bluefin tuna and pufferfish (Fugu) threatened with extinction http://t.co/sQO8mW6Cbv via @TIME — Elizabeth Auerbach (@ElizabethOnFood) November 18, 2014

— Robert Ferris, CNBC