Nymphing without the aid of a strike indicator is all the rage in the fly fishing world, but there are plenty of times when tying on that Thingamabobber is the correct course of action.  

The trouble is, the assistance of a strike indicator doesn’t necessarily mean easy times ahead for the nymph fisher. There are things we can do, and things we shouldn’t do, to make sure we fish our flies properly and use the indicator to our full advantage.

The idea behind a strike indicator is simple:  attach one onto your leader and use it as a method of detecting strikes on your flies underneath.  

It all seems easy enough, but the trouble is there are many factors at play and fly anglers must take most, if not all, into account.

Above all factors, an angler must take notice of the depth of water, and the current speed and direction in which they are fishing.  Those two variables play a huge role in determining our success nymphing under an indicator.

Calculating Depth & Placement of Indicator

Starting with the depth, we should strive to fish nymphs almost twice as deep as the depth of water being fished.  

Why 2x as deep? Why not make it exactly the same depth?

Here’s why. As your nymphing rig drifts down stream, everything below your indicator will adjust to the speed of the current underwater, which may be differen than the speed you see on the surface.

Eventually, the current will push your flies downstream of your indicator, thus, creating an angle as it leads in front. As a result, you must factor in more line to compensate for that angle so that your flies are still near the bottom.

Here’s a simple guide to adjusting your indicator based on depth and current speed:

  • 2x depth – Medium fast to extremely fast currents
  • 1.5x depth – Medium fast currents
  • 1x depth – Extremely slow currents

That’s sometimes difficult if it’s a particularly deep hole of say, five or six feet. If you’re not entirely sure, it’s better to go a bit too deep rather than too shallow.  After all, nymphs are designed to mimic bugs that would be crawling around on the stream bottom, so it’s imperative those flies be fished on the bottom.  

When fishing a new spot, set the strike indicator a little higher than your instincts might call for. If the first few casts get snagged, adjust, but odds are fishing a little deeper will yield excellent results.

Adjusting for Water Currents

A more difficult challenge is how to adjust the indicator for water currents.  Everyone has heard of the drag-free drift, and its importance to nymphing, but the variable not often talked about is the role of the strike indicator.  If currents are swirling and it’s anything but a straight-forward upstream to downstream drift, take notice of the indicator in relation to our flies.

On guide trips, I’ll spend the first few drifts in a spot watching nothing but the indicator.  

Does it push or pull in previously unforeseen directions?

Is it moving faster or slower than anticipated?

Once those things are determined, anglers can artificially adjust to play into the current. In particularly swift currents, that can mean going to a larger size indicator.  In slower currents, or extremely clear water, using a more discreet pinch-on indicator can help limit our impact on the fish.

Be willing to adjust throughout the day.  Before flies, leader size, tippet size, or weights are changed, adjust the indicator.  Observing how it behaves can be an excellent representation of how the flies are moving just underneath!  Pay attention to the push and pull of currents along with the depth of the water, and use the assistance of a strike indicator to help catch more fish on nymph rigs.