Cherry Salmon

Cherry salmon (Oncorhynchus masou) is a Pacific salmon species native to coastal rivers of Japan, Korea, and the Russian Far East. It is notable among Pacific salmon for producing two distinct life-history forms from the same species: an anadromous form that migrates to sea and returns to spawn, and a smaller, non-migratory freshwater-resident form known as yamame that remains in rivers its entire life. The common name references the pinkish hue spawning fish develop, resembling cherry blossoms. Cherry salmon populations have declined in parts of their range due to river damming and habitat alteration, and some regional populations are subject to conservation and habitat restoration efforts.

Cherry salmon identification depends heavily on which life-history form is observed:

• Freshwater-resident form (yamame): smaller, silvery-olive body retaining oval parr marks along the sides into adulthood, with scattered small black spots on the back
• Sea-run form: larger and more uniformly silvery after time at sea, losing much of the parr marking, developing a pinkish flush and hooked jaw (kype) at spawning
• Both forms share a slender, streamlined salmonid body, small adipose fin, and forked tail
• Black spots are present on the back and dorsal fin but are generally smaller and less dense than in some other Pacific salmon
• Sea-run adults typically reach up to about 50 cm, while river-resident yamame are usually smaller

Cherry salmon are native to cool coastal rivers and streams of Japan, the Korean Peninsula, and the Russian Far East, including Sakhalin and Kamchatka. The anadromous form migrates from natal rivers to the North Pacific and Sea of Japan to feed and mature before returning to spawn, while the resident yamame form remains permanently in cool, clear headwater streams, often above natural barriers such as waterfalls that block access to the sea. Both forms require cold, well-oxygenated water and clean gravel substrate for spawning. River damming and habitat fragmentation have reduced access to historic spawning grounds in parts of the species' range.

Cherry salmon exhibit a flexible life-history strategy, with some individuals migrating to sea while others, particularly in headwater habitats blocked by natural barriers, remain resident in freshwater their entire lives as yamame. Sea-run fish feed on small fish, crustaceans, and other prey in the ocean before returning to their natal rivers, while resident yamame feed on aquatic and terrestrial insects. Spawning occurs in autumn, when adults migrate upstream to gravel-bottomed sections of river to build redds and lay eggs, after which most anadromous adults die, following the typical semelparous salmon life cycle. This dual life-history strategy helps buffer populations against environmental changes affecting ocean survival.