How Trout See Flies at Night

In an article about anglers’ odd obsessions in London’s Times Online, author Brian Clarke explains how his research for his book The Trout and the Fly led him to discover the reason that surface insects are easily visible to trout at night. “We had our answer at once. It was that wherever part of a fly — feet, body, wings — touched the surface tension, they dented it slightly. This distortion, when viewed from below, acted rather like a lens — it gathered and concentrated any light remaining in the night sky. The result was that, from the position of a trout looking up, each fly on the surface was brightly outlined against the darkness all about it.”
The Trout and the Fly on Amazon.