In the Yesanpo Scenic Area in Laishui County (also known as Yi County) in Hebei Province, it is said that before and after Guyu every year, the mountain springs here will spew out a large number of fresh fish. Each fish weighs about six to seven taels, has black spine and white belly, delicious meat and hard bones. The locals call it "stone mouth fish".

According to expert observations, this "stone mouth fish" is a multi-squamous mandibular fish.