The TGA carried out a number of Invertebrate Samplings on the rivers Ericht, Ardle, Shee, Lochay, Dean and Lyon in 2021. 2022 and 2023. These samplings are done under the auspices of the WildFish charity which is a major advocate of ensuring our rivers are clean and unpolluted to ensure the survival of wild fish.
A typical sampling report (this one from the River Lyon) is here
SmartRivers-Lyon-autumn-2023-1.pdf
A description of what the results mean is here
Our rivers appeared to be in a healthy condition as summarised in the WildFish Report for 2022
2022-SmartRivers-data-update-1.pdf
Snapshots of where we stand against other rivers are in the following images:

