The upper section covering about 20km from the township of Kyongsong County, North Hamgyong Province to Phoro Stream, a tributary of Kwanmo Stream, is the habitat of Dolly trout at Kwanmo-ri.

The trout is a species of anadromous fish which migrated up to the fresh water in the alpine region and survived in the ice age.

It was designated as a natural monument and is under protection and propagation as it adds more beauty to the landscape of rivers and streams in the Kyongsong area and is of significance in increasing the fish resources.