The Rede is one of only two rivers in the North East of England that has the freshwater pearl mussel in its waters.

The source of the river is on Carter Fell, part of the Whitelee National Nature Reserve.

[1] It flows in a south-easterly direction and is the main feeder for the Catcleugh Reservoir which was impounded in 1901 and completed in 1905.

In the lower reaches, the landscape changes slightly to grassland and upland heath with underlying boulder clay, alluvium and peat.

The fish were bred at the Kielder hatchery and had microscopic pearl mussel larvae attached to their gills.