Comment by RajT88

The river I live next to had the same thing happen. The mussel populations aren't what they once were (said to be hundreds per square meter back in the 1800's). There was also button factories along the river, and they briefly tried pearl farming. The big problem was pollution, dams, etc. as you say. The river is better now than it's been since I was born - and more dams are being removed year by year.