The River Fergus is a 37-mile limestone river flowing through County Clare in the west of Ireland, draining a rich catchment of 402 square miles that includes numerous interconnected loughs. Rising northwest of Corofin in the Burren — Europe's largest area of limestone pavement — the river winds slowly and clear through Kilnaboy, Corofin, Ennis, and Newmarket-on-Fergus before entering the tidal Shannon estuary. The Fergus is a gin-clear, slow-moving river that is nationally recognized as a noted brown trout dry-fly fishery, while its lower reaches offer a worthwhile spring salmon fishery. The limestone geology gives the water exceptional richness, supporting dense invertebrate populations and producing trout that grow deep and fat. The river passes through Inchiquin Lake in its upper reaches and Ballyallia Lake just north of Ennis, with several other small lakes along the way contributing additional food sources for the river's trout population.