Artist's impression of what Jomon river weir looked like
Yomiuri Shimbun (9/28/2002)
Seventeen fishing traps or weirs believed to have been placed in a river about 4,000 years ago have been discovered at an archaeological site in Ishikari, Hokkaido, the Ishikari City Board of Education said Thursday.
The site, Ishikari Momijiyama No. 49, is said to have the oldest and largest remains in the nation that indicate fishing took place in ancient rivers.
Heritage of Japan 