Minding the Column: Match The Hatch on the San Juan River

The weather patterns and bug cycles can vary wildly through the seasons on the San Juan and you need to be able to adapt to the prevailing conditions and trends. So what should you be thinking about when fishing?

About Trout on the San Juan

While this seems painfully obvious, we need to think beyond the mundane. Trout are:

• cold blooded
• generally like to “drift feed”
• keen to bug cycles
• move depending on conditions in water, weather, & food availability

The colder the water, the more sluggish and slower the fishes metabolisms become. While the San Juan is a tail water, ambient air temperature affects water temperature the further you get away from the dam. Even a change in a couple degrees can have an impact on where the fish are holding.

When asking yourself where they are, you want to consider the water column. As guides, we generally break it into thirds. Lower, middle, and upper third are the terms you want to get familiar with. Trout will are generally lazy fish and if there is no reason for them to fight the current (i.e food), they will generally hold deeper where the water is slower. River current is not congruent in these thirds. The closer you get to the bottom, the slower the current as the river is slowed down by friction.

Where the trout hold is greatly impacted by bug activity and the intensity thereof. While there are aquatic worms, scuds, and other macro invertebrates present in the Juan, the two bugs we get most excited over are beats (mayflies) and midges.

Bugs

Scuds and aquatic worms are preyed on by trout in the lower third of the water column as that’s where they spend their life. Baetis and midges both have life cycles that start in the lower third of the column (nymph/larva) and move through the middle (emerger/pupa) and upper third (emerger/pupa/adult) at the end of their life cycle.

The San Juan has beats and midge activity daily at varying degrees throughout the year. It is important to understand what form of the insect the trout is eating and tailor your rig accordingly. Many times I have seen huge hatches of baetis and midge adults and the trout were just a few inches below the surface feasting on the emerger stage of the insects. Rather than “match the hatch” try and “match the column”.

Midges

Midge patterns make the up the bulk of my guide boxes and chances are I’m fishing some form of their life cycle throughout the day. Usually before the water warms and the hatch is going, I fish deeper with larva patterns. As the hatch intensifies, usually a lighter rig, fishing mid column with pupa is the ticket. If I see trout backs and tails but no heads eating adults, a shallow light rig in the first 2ft of the water column is usually a standard. Sometimes you can force feed “midging” fish a dry, but sometimes you can’t. Paying attention to where you see trout in the water column can clue you in on what they want and how deep or shallow you should be fishing.

Mayflies/BWO/Baetis

Just like midges, baetis or blue wing olives are a staple on the San Juan. Also like midges, trout will be feeding on various forms of their life cycle throughout the day. Again, earlier in the morning the nymph stage will be important. As bugs begin to hatch using the emerger stage or adult (dry fly) will be productive.

Putting it all together

Next time you make it out to the San Juan, think “trout first” and then mind the column. By letting the trout and insects tell you how to rig, it will greatly help in demystifying the river. One thing I have learned as a guide on the Juan is that it’s more important to change your depth and weight before you change bugs. Fishing the “wrong” fly in the right way is more productive than fishing outside of a trout’s feeding zone or water type. One final note is that I’d rather be over a trout than under them. Trout are more likely to tilt their head up to feed than drop their head and eat below themselves. While there are many exceptions, this is a generality that I often come back to when rigging clients. Next time you’re on the river and she throws you a curve ball, remember to mind the column. I hope this little piece helps put a few more trout in the bag on your next visit to one of Americas greatest tail waters.