Is the "noodle fish" thunderfish a sea fish or a river fish? Is it an irradiated fish? How do you cook it?

Thunder fish is the general name of many kinds of translucent fish of the family Silverfish in Japan. it is a kind of high-protein and low-fat food, which is also suitable for patients with hyperlipidemia. Is it a sea fish or a river fish? Is it an irradiated fish? How do you cook it? According to the data of the silverfish family,