The toxin is in tiny concentrations of the fish's muscle which is normally eaten. The parts that can't be eaten are mainly the liver and ovaries, where the toxi

The toxin is in tiny concentrations of the fish's muscle which is normally eaten. The parts that can't be eaten are mainly the liver and ovaries, where the toxin is most concentrated. Interestingly, there are traditional fermentation processes by which the toxin level in the liver and ovaries can be reduced to similar levels to the normal edible parts over a couple of years, which have managed to survive despite prohibition of fugu in Japan during the Edo period.