Iwame trout

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Iwame trout
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Salmoniformes
Family: Salmonidae
Genus: Oncorhynchus
Species: O. iwame
Binomial name
Oncorhynchus iwame
Seiro Kimura & M. Nakamura, 1961

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 for some time, it was recently confirmed to be a particular intra-specific morph occurring in some populations of the masu salmon or seema (Oncorhynchus masou). This morph is recessively inherited.

This morph occurs in the amago subspecies ((Oncorhynchus masou ishikawae) and apparently also in the nominate subspecies yamame (Oncorhynchus masou masou), if these are not identical.


  • Kano, Y., Shimizu, Y., Kondou, K. 2006. Sympatric, simultaneous, and random mating between markless trout (iwame; Oncorhynchus iwame) and red-spotted masu salmon (amago; Oncorhynchus masou ishikawae). Zoological Science 23:71-77. doi:10.2108/zsj.23.71
  • Kano, Y., Kondou, K., Shimizu, Y. 2009. Present status and conservation of the markless forms of stream-resident masu salmon Oncorhynchus masou (the so-called 'iwame') in Japanese mountain streams. Ichthyological Research 57:78-84 doi:10.1007/s10228-009-0130-1
  • Kottelat, M. 1996. Oncorhynchus iwame. 2006 IUCN Red List of Threatened Species. Downloaded on 4 August 2007.