The River Esk is one of North Yorkshire's most celebrated salmon and sea trout rivers, flowing approximately 28 miles from its origins in the blanket bogs between Baysdale and Westerdale — an area known as the Esklets — through the heart of the North York Moors National Park before meeting the North Sea at Whitby. Along its journey, the river passes through a richly varied landscape of upland heather moorland, deep wooded valleys, and traditional stone-built villages, creating a diverse range of fishing habitats. The Esk is a freestone river, clean and healthy owing to its rural character, and supports a remarkable wealth of wildlife including salmon, sea trout, brown trout, and grayling. It is also the only river in Yorkshire known to hold freshwater pearl mussels, a critically endangered species that depends on clean, fast-flowing water and healthy salmonid populations. The Esk Fishery Association has been managing and fishing this water since 1864, currently covering around 8 miles of river bank with a membership of between 70 and 80 anglers.