The River Calder flows through the heart of West Yorkshire, England, winding through a landscape shaped by centuries of industrial history and ongoing ecological recovery. Originating in the upland Pennines, the river passes through towns including Huddersfield, Mirfield, Dewsbury, and Wakefield before joining the River Aire near Castleford. Once heavily degraded by textile and chemical industries, the Calder has undergone significant improvement in water quality over recent decades, and today offers a surprisingly diverse range of fishing opportunities across its length. The river is a dynamic, mixed fishery — transitioning from cleaner, faster-flowing game fish habitat in its upper reaches to productive coarse fishing water through its middle and lower sections. The return of otters and kingfishers to the river is a testament to how far the Calder's ecological recovery has come, and salmon have even been sighted in the lower river, signaling continued improvement.