White Spotted Char / Iwana or Ame Masu

2011/9/14 White Spotted Char / Iwana or Ame Masu

White Spotted Char / Iwana [jp]
Salvelinus leucomaenis (Pallas, 1814)


Once known as “phantom fish” in main island for reduced number of population, but they have become thoroughly available in mountain streams of Japan in recent years due to stocking.

Iwana came to Japan from Arctic Ocean during the Ice Age, then fish in southern habitat got landlocked as global climate warmed up and blocked them from returning to ocean.  They headed for the coldest water they could find, and it is why Iwana is often seen in very small mountain streams where water is only a foot deep, and they move about large distance in rainy season when water becomes deep enough or rainy day when they crawl from one stream to another.

Amemasu or Ezo Iwana: Dominant Species of Iwana

Amemasu are found in Hokkaido and part of Tohoku Province and they are dominant species of iwana who are found in both landlocked and searun. On the contrary to iwana who was regarded as “phantom” in other area, amemasu was considered low priority in game fishing for its high abundance.

Other Subspecies of Salvelinus Leucomaenis


1: Nikko Iwana: Salvelinus leucomaenis pluvius (Hilgendorf, 1876)

Most abundant iwana in Eastern Japan including near Tokyo, and  extending their habitats all the way to Western Japan by stocking.

2: Yamato Iwana: Salvelinus leucomaenis japonicus (Oshima, 1938)

Labeled as “endangered” or “vulnearble” speci on Red List due to over fishing and mix breeding with pluvius caused by recreational fishery. It is hard to preserve this subspeci due to indentity method is not widely known. Major difference between Yamato (japonicus) and Nikko (pluvius) is that Yamato doesn’t have white spot scattered on its back.

3: Gogi: Salvelinus leucomaenis imbrius (Jordan and McGregor,1925)

Local subspeci of Chugoku Province labled as “vulnearble” in Red List.