The Angler is a Predator
Trout are scared. All the time. The Osprey, Heron, Otter, Kingfisher, angler, and other fish constantly have them paranoid. You would be too. Mature trout don't risk it. If suspicious shadows, sounds, or errant casts/drifts are noticed... a big trout will shut down feeding and lay low. While we can't control all factors, but we can control how we approach trout water to avoid being seen, spooking fish, and not fighting against unwillfull currents.
A "spooked" trout isn't necessarily one that flees the pool at 120 miles an hour. It's a trout has simply become "aware" of some outside forces and elects to discontinue feeding. Which is pretty easy for them to to do. Just lay low, don't eat the stranger's candy. As you head out on your next adventure, keep in mind that a wary ol' mature trout only has to suspect something is wrong and they win!
Tips on Approaching and Reading Water
- Use the fewest number of casts to catch the most possible fish.
Your goal should be to show the fly to the fish only 1-2 times. Larger trout typically aren't fooled by repetive drifts.
- If you are casting over slow water toward faster water, approach by casting and wading upstream. Assuming you are fishing nymphs or dry flies. Inversely, if you are casting over the top of fast currents toward slower currents, your best approach is angling downstream with your cast, drift, and wading.
- Shadows are scary. Pay attention to the sun angle.
- Move slow. If you need to move in close to the fish, like when Euro Nymphing, just move slow. Be the tree.
- Walk quietly. Don't splash, kick rocks, etc. Give the fish some credit. They are prey.
Try to catch a fish every cast. This may sound stupid yea, but if you treated every presentation like it was the only one you get it would change things.
- One cast, one fish. Perfect drifts, in slightly fresh water every time.