Holmengrå is the only place in Hordaland where we find traces of the abrasion that is supposed to have transformed Western Norway from a Himalaya-like high mountain landscape during the earth's Paleozoic Era, to a flat lowlands terrain during the Mezosoic Era. Just 400 million years ago, large and small stones plummeted down from the high mountains. Some of these stones became incorporated into the conglomerate bedrock on Holmengrå.
At the southern end of the bridge between Radøy and Fosnøy archaeologists found an unusual Stone Age settlement. There was a thick “cultural layer” here with the remains of the waste dumps of a hunting people. The place was called Kotedalen. Here they came, one group after the other, and settled for some weeks, some months, or maybe years before they went on, leaving the settlement deserted. Time after time it happened. At least 16 settlement phases have been identified, stretching over 5,500 years.
From times immemorial salmon and trout have been caught with various tools in the fjord and the streams here. Finds in the Stone Age settlements at Skipshelleren indicate that salmon was probably caught by angling. Nets, fish pots and traps have been used in the rivers right up to our times. In the fjords the use of nets was developed into a salmon seine around 1500, and later into what today is known as fixed seine.