If you have read my blog posts or book you know that I’m always telling you to nymph in the bottom strike zone, meaning, the level in the water column from the river bottom to about a foot and half above the bottom. Trout spend the majority of their time in the bottom strike zone so it makes sense that you should spend the majority of your time nymphing in that zone. However, there are two occasions when nymphing on the bottom is not effective and you should elevate your nymphs off the bottom.
The first occasion that I would elevate my nymphs above the bottom strike zone is during an abundant aquatic insect hatch and you physically see trout rising at the surface. The key words here are “abundant” and “rising” because you only want to raise your nymphs off the bottom if trout are elevated off the bottom as well. Trout will elevate off the bottom to the middle and surface water column levels to more easily feed on surface insects, but they will normally only elevate in position if there are many insects to feed on. Currents are faster at the surface than at the bottom, so if a fish raises off the bottom it has to be an energy efficient trade-off. In other words, if it cost more energy for trout to fight the surface currents than their taking in by feeding on surface insects, it is not worth it for them to rise in the water column. Trout will occasionally rise to surface insects when an abundant hatch is absent, but these are the few aggressive trout that are most likely rising from the bottom strike zone anyways and nymphing in the bottom strike zone probably would have resulted in them biting as well.
Even when trout are rising on the surface, trout are often feeding on the emerging insect stages. Meaning, the insect stage between a bottom dwelling nymph and a surface flying adult. Many rises at the surface are actually trout feeding just below the surface on emerging insects. Often, a few trout will target the surface stage but the majority of trout are actually targeting the emerging stage. You want to elevate your nymphs off the bottom when trout are targeting emerging nymphs in the upper water column.
The second occasion that I would elevate my nymphs above the bottom strike zone is during the very early morning and very late evening in the first and last hour of day light each day. If the sun rises at 7AM, I’d raise my nymphs off the bottom from about 6:30 – 7:30 AM. You want to elevate your nymphs off the bottom during these times because trout have a hard time seeing your flies during these periods. Your nymphs will blend in with the river bottom if they are right on the bottom during these time periods, but will be more visible if you raise them up in the water column where there is more sunlight. In other words, the nymphs profile will stand out more to a trout with the blue or white sky as the background instead of the dark river bottom as the background.
More information on trout nymphing can be found in my guide book SIMPLE NYMPHING FOR TROUT IN RIVERS & STREAMS.
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