There are smaller triangles within the bigger triangles. These pockets, as anglers call them, are caused by seen or unseen obstructions and riverbed features. A fast-water pocket, viewed from the surface, can seem a torrential, hostile environment, but all are fishholding areas. Fish view their multipaced environment differently to us. They know all about feature, structure and flow; a triangle to a fish is prime territory and even in the fastest flow a small boulder can give them shelter under a broken turbulent surface. A key difference between the mainflow triangle and the pocket triangle is the reversal of fast- and slow-flowing water. In the main flow of a pool, fast water is central with slow water on the edges. But in a pocket triangle, slow water is completely surrounded by fast water and turbulence. However, both triangles have the same fish-holding feature: the crease. In a small pocket, fish will tend to be in ones or twos, sitting centrally and moving off station to take food. In large pockets, behind bigger obstructions, or multiple breaks in flow, you will find more fish, due to less competition for food over a larger area. Broken water like this can hold large numbers of fish and to fish effectively you need to cover numerous areas with your flies.
Pockets with slow centres