Blowfish Ovaries Pickled in Rice-bran Paste

What are blowfish ovaries pickled in rice-bran paste?

In Japan there is a type of pickle called nukazuke, or rice-bran pickles. Rice bran is a powder that consists of the seed coat and germ that is removed from brown rice when it is turned into white rice. It contains nutrients such as protein and vitamin B1. Vegetables or other foods pickled in a fermented mixture of rice bran, called nukadoko, and salt for flavoring, are called nukazuke
"Blowfish ovaries pickled in rice-bran paste" is a food that has been aged at least three years. It is said to be "unique in the world" and "a miraculous food".
This is because they contain so much deadly poison that, although the strength is different depending on the type of blowfish, if you put the ovaries in your mouth as they are, you will be poisoned to death. Pickling the ovaries in salt and rice bran de-poisons them?they become safe to eat and very flavorful.
The only places in Japan where "blowfish ovaries pickled in rice-bran paste " is made are the Mikawa district of Hakusan City, the Ono and Kanaiwa districts of Kanazawa City, and Wajima City, all in Ishikawa Prefecture. It is not clear when people started to make this type of pickle in Ishikawa. Also, there is no scientific explanation for why the poison in the ovaries is removed during by pickling?the de-poisoning process is still a mystery. Therefore, none of the producers can change their method of production. "Blowfish ovaries pickled in rice bran " is still being made using the same traditional methods as ever.

• What are blowfish ovaries pickled in rice-bran paste?
• How are they made?
• How can the poison be removed?