This is one of my favorite winter fish delicacies, a fish commonly referred to in English as rainbow trout, it is a red-spotted masu trout. Caught in the local waters in Shizuoka prefecture, the rivers here are abundant in fresh cold water, and valleys produce the finest wasabi. Local rivers are famous for its rich fish stock; iwana (char), yamame, niji-masu (raibow trout), as well as other kinds of sweet water fish.
Extraordinary in taste, this small fish has plenty of flesh to eat. It is prepared over sumi-bincho at the kitchen of Yagyunosho, my favorite onsen in Shuzenji. Amago in the winter are more hearty and have more body fat as opposed to the summer when they are younger and leaner.
These river fish have a particular taste due to their diet, hence the taste is more accented by what they eat. Feeding on crustaceans and other fish in coastal waters so in the summer they taste can vary due to the local climate.
On the Pacific Ocean side of Japan, from Hokkaido through Honshu, Shikoku and Kyushu, Amago are commonly found in mountainous rivers and streams. These fish are very well-preserved in the waters below 15°C.
Amago remain in rivers for the entire life cycle, but some migrate to the ocean. They undergo physiological changes to adapt to salt water, and return to the same mountain streams where they were spawned. Unlike other species of salmon, most amago don’t stray far, and mostly Juveniles migrate to the sea in autumn, and return to their home streams the following spring.
When the fish finally reach the stream where they were hatched, the female digs a nest in the stream bed and lays 2,00 to 7,000 eggs. The male then covers the eggs in milt (sperm) to fertilize them. Both sexes are exhausted and then die.