Did I Spook Him?

As a fishing guide, I'm asked a million questions by my clients.  "Why this fly?" "Why approach from that angle?"  "What's wrong with my cast?" and so on.  Some questions are easier to answer than others, of course, and many of the the best questions come from clients who don't necessarily agree with my contrarion trout theology:  trout are stupid, lazy, and their eyesight ain't all it's cracked up to be, among other sacrilegious teachings.  They challenge me to PROVE to them that I'm right, and the debates are usually a lot of fun -- generally because I win.

The question above is one I've been asked many many times.  Actually, all the questions are asked repeatedly, but this is one question with an answer I have not been able to prove until now. Here's the origin story:

The Meramec River is the primary destination where I guide clients, and Meramec trout are NOTORIOUS for super-quick bites.  And since they're generally hesitant to look to the surface for food, that often means nymphing deep water and setting the hook on nearly invisible hits.  Over the years, I've discovered that one fairly common challenge for the typical trout fisherman is (1) seeing the hit, and (2) responding quickly enough.  In practice, it turns into a lot of missed hook-sets.  And when a client sees what looks like a hit and sets the hook to feel nothing pulling back on the end, a common question is: "Did I just spook that fish, or should I keep casting to him?" 

My answer has always been the same:  if the fish didn't feel any pain from the hook, then he'll keep biting until the experience begins to make him nervous.  In other words, even after you start thinking "that must just be a clump of weeds grabbing my fly," keep casting to the same drift until the river proves that it's not a fish. Need proof?  Here y'ar. And you're welcome.