You bring up an interesting salmon. This little guy is found in Russia, Japan, Formosa and Korea. There are a number of sub species found through out the area. It was introduce to Washington State and Michigan and it did not take. I suspect that it had too much competition from our NW salmon and trout to thrive. It has even been tried for aquaculture-- I havent heard how that one went.
Anyone been to Lake Biwa?? Apparently there is a sport fishery for them in the lake.