Its not necessarily an error. I grew up in the area and the reservoir had wild brown trout in ( a small burn provided some spawning) and a mayfly hatch some years! Later it was stocked with rainbow trout but occasional big brownies came to the fly especially near to the rocky deeper section in the corner distant from the dam. Recently I've heard its run as a coarse fishery and shocked this was allowed by the Environment Agnecy if they are stocking with coarse fish. It always had some perch but they are native to the UK.

This is obviously an error as this appears to be Lockwood Beck Reservoir.