I'll mention again all the road salt that the city of Calgary started liberally laying down on icey roads all over the city for the last 5 winter's, for year's it was pea gravel but now it's a mix called pickile, road salt/pea gravel, when the snow and ice melt, the melt water with all of the salt goes into storm drains that run directly untreated into the river, the cities storm drains smell like the ocean in the spring.
The asphalt roads in this city are burnt by the salt, they use to be black, now they are white and grey from all the salt.
If the roads are burnt imagine all of the creatures that used to live in the water...it seems obvious, fresh water fish don't do well in salt water...I imagine the same is true for fresh water invertebrates.