Step one is don't let companies dump industrial waste in your local water supply. It happens every fucking day, because no one takes out a camera literally in their pocket all the time! and takes a picture of it happening so it can be reported.
Step two is push your mayor to do better water sanitation. All your poop is collected, mixed with a buffer, and sprayed into nearby rivers with little to no treatment. This kills your water supply. So start writing letters to mayor.
Step three is get a fishermans license or join a fishermans club and begin pestering the club to engage in restocking. If they can't afford restocking, get them to think about roughing up the shoreline. Fish love rough shorelines, with semi-aquatic trees, shrubs and grasses to provide cover for the newly hatched fry. Your fishing club can do as little as buying a few bags of seeds from marsh loving plants and emptying them out in a few choice spots along the riverbank.
Do these 3 things and you got yourself a ready made food and water supply next to every city.