last great ice age as a huge wall of ice moved across the landscape carving out what is now the Esk Valley as far as Lealholm. At its head it formed a massive dam blocking the flow of water from above and creating a lake running back up the valley to Commondale. As the ice melted, the river forced its way out carving the ravine we see today. In Victorian times, the Ghyll was home to a large rockery garden, open to the public, but long since washed away by flooding of the river. The small villages along the river were at one time of great importance to the north-east, with coal mined in the valleys, and iron ore dug from quarries on the surrounding moors. Today, all that remains are the deserted mine shafts, though potash is mined, near Boulby, with tunnels running six miles beneath the sea, some of the deepest in Europe. Of the major rivers in Yorkshire (as defined by the Environment Agency), the Esk is the only one to flow into the North Sea directly without flowing into either the River Tees or the Humber Estuary. River Esk Tideway Byelaw 1987 Since 1987 a byelaw has been in place to protect dangerously dwindling populations of salmon and sea trout. The River Esk Tideway Byelaw 1987, prevents fishing for salmon and sea trout along the stretch of the Esk between Ruswarp and Whitby known as the tideway. The Environment Agency enforces the byelaw under s210 and Schedule 25 of the Water Resources Act 1991. The byelaw was renewed in 1997 for 5 years, then again in 2002 for 10 years. After a peak of 924 rod-caught salmon per year in 1965, the number dropped to just 11 in 1989. This was due mainly to illegal poaching of stocks from this stretch under the guise of angling. Since the byelaw was introduced and enforced, the numbers of rod-caught salmon per year, further upstream, has increased each year (to 177 in 2010). The byelaw was due to expire in 2012, but was further extended to the end of December 2018. Recreation The river is used for boating in the lower reaches, especially in the upper and lower harbour areas of Whitby town. The two harbour areas also function as a port for commercial shipping and for the fishing industry. Sea-fishing tours operate out to sea from the harbours