Sheffield's industrial past saw the implementation of weirs on the River Don to power the factories. These flow control devices inhibit natural migratory paths for fish. To combat this, fish passes have been installed at the weirs throughout Sheffield. These are important for the movement of fish (particularly salmon) between habitats and breeding grounds. The Don Catchment Rivers Trust have been working on the River Don to bring back the salmon population to the area and now efforts are needed to maintain this. GoodGymers will be part of long term surveying and monitoring of the fish passes to ensure they have not been blocked and remain fully functional.