Powerful Pennine spate river rising at Cross Fell — wild, dramatic water that demands respect. Upper Tees above High Force is spectacular: fast boulder-strewn runs with muscular wild trout that feed aggressively. Below Barnard Castle the river calms into longer pools with good grayling and recovering salmon. Nymphing (particularly stonefly) is often more effective than dry fly in the heavy water; when hatches are on, trout respond to big, bushy dry flies that float well in turbulence. Heavy tippet and wading confidence matter more than delicate presentation. Wild brown trout fishing is the main draw; salmon and grayling secondary. Spring-fed limestone underlies this river. Atlantic salmon are assessed by the Environment Agency against each river's Conservation Limit — many principal rivers are classed 'at risk' with mandatory catch-and-release byelaws; check current rules before fishing.

• Limestone

• Ecology: Moderate
• Chemical: Fail