The satsukimasu salmon, red-spotted masu salmon or amago (Oncorhynchus masou ishikawai) is a salmonid fish in the Pacific salmon genus Oncorhynchus

Oncorhynchus

Oncorhynchus is a genus of fish in the family Salmonidae; it contains the Pacific salmons and Pacific trouts. The name of the genus is derived from the Greek onkos and rynchos , in reference to the hooked jaws of males in the mating season .-Range:Salmon and trout with ranges generally in waters...

. It is endemic to Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

.

It was initially described as a distinct species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 and was cited as such by IUCN, but it is more lately often considered a subspecies

Subspecies

Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

 of the masu salmon or seema (Oncorhynchus masou). Others, including FishBase

FishBase

FishBase is a comprehensive database of information about fish species . It is the largest and most extensively accessed online database on adult finfish on the web...

, and Catalog of Fishes do not consider it taxonomically distinct from O. masou masou.

The Iwame trout

Iwame trout

The iwame trout or markless trout, Oncorhynchus masou var. iwame, is a variety of salmonid fish inhabiting some fresh waters of Japan. Suspected to be not a real species since some time, it was recently confirmed to be a particular intra-specific morph occurring in some populations of the masu...

 in turn was recently confirmed to refer in part to an unspotted recessive morph of the amago.