They are experiencing that here on the Yakima River in Eastern Washington. The Yakima is a slow moving river and most always dingy brown from sediment runoff from irrigation return water. Modern farming practices have removed the heavy sediment load and now the river is clear. A few years ago the Dept. of Ecology proposed to eliminate phosphorous in the in waste water returns to the river because the river is now full of algae and other aquatic plant life because with the new clarity and sun light is causing them to bloom.
Oh, those unintended consequences, ain’t they a bitch.
Interesting.
What green activists see as proper water is good for human consumption and not what the fish want.
Sort of like a parent covering up a sleeping child, because the parent is cold.