is not suprising.
Freshwater? lol I dont think so
in NZ rivers are dirty too. we are told never to drink from them as risk of getting giardia. a lot of farmers never cared to fence them off to stop stock from going into them and had septic tanks and fertilisers running off into them like they were giant sewers.
People chuck supermarket trolleys in them and kinda treat it like the ganges in India where they dump dead bodies. Then they remove the mangroves and reeds and wetlands which are filtering the salt and everything coming the other way, Oh and BABY wipes block everything up.
Its disgusting. Fish dont wanna live in that mess.