Winter is dragging… Ice forces you to new waters.  Instead of blindly grabbing your favorite nymph from your box and fishing an entire reach without as much as a look, you are actually lifting rocks, digging through mud and vege, and collecting insects you eagerly hope to identify.The day is young, steam rises as the sun creeps over the ridge into the canyon.  Fishy noses are likely going to be non-existent, but you assume they are eating something subsurface.  You pull another freezing, slippery rock from the streambed crawling with tiny buglets you don’t recognize…   Not a big deal.  Really.

I remember those days.

Since those moments of uncertainty and psychosis, I have concluded that fundamental and basic principles that can be simplified are key to understanding aquatic ecology and ultimately lead to more fish in the net.  Not that I don’t want to teach everything I know, but rather, I have prioritized some tips and entomology basics that will help you make leaps and bounds in a buggy-bug world as opposed to tiny, baby steps.  The first step of entomology and ultimately catching more fish is determining GENERALLY what type of bugs are in the drift … Get it? The drift?

Here’s a few generalizations that are fundamental to understanding why drift is so important.  

  • Fish in a stream aren’t constantly moving around, actively searching for food items (in a general sense).  They let the food DRIFT to them.  As fish feed on items that they see often, they begin to key on those items making it harder to catch them on less recognizable entrées. Like when you throw a seemingly giant, delicious stonefly when fish are eating midges.  You are like, “come one Eugene!  Just eat it!”  It’s exactly like you eating burgers everyday then some dude throws you a pile of  Blanquette de veau, and you are like, “what the heck is that?”    So…..
  • Ask yourself, what are the most abundant items in this stream?  Depends on the stream, but there are usually some assumptions that can be made.   Making a general synopsis of relative abundance of the bugs in a particular stream can make fly selection much easier.  Think simple and you will be rewarded.   Even if you don’t know the genus and species of an abundant bug in the river, look at it generally. Most of the bugs are light? Go light.  Most of the bugs are BIG and DARK?  Go big and dark. You have all heard the saying, “Size, then profile, then color.”  = FACT

For you experts out there, here’s a couple more random, bonus, interesting, and yes, applicable facts and tips:

  • Many mayfly nymphs (baetis especially) drift behaviorally (that is, they let go of their rocks on purpose to distribute, find food,  space, etc).   They do so more often just before dark, and throughout the night to avoid predation by trout. Mayflies can detect/smell if fish are present in a stream.  If the stream is fishless, mayflies will drift more during the day. No kidding…
  • Use a stomach pump!. (See Brian Chan’s video posted in comments for last entomology post HERE).    I will forever continue to stress the usefulness of  this.  Just Friday, I was on a local river curious about what the fish were eating.  I pumped the first fish I caught which produced a handful of 30+ sowbugs. Game over………. 35+ fish in a few hours. (Remember the rollie pollies, potatoe bugs, and pill bugs as a kid? Here’s the aquatic version).  NOTE* These are NOT scuds!
If you have helpful info to share or specific questions please leave them in the comments section and we’ll reply with answers or cover them in future posts!


About The Author

The Professor

Phil Tuttle is a Fisheries Biologist, a Guide, Loop Global Team Pro Staff Member, Fly Innovator, and a skilled Videographer/Video Editor. His passion for conservation, travel, youth fishing programs, and fly fishing drive his desire to promote the sport in diverse and out-of-the-box ways.

6 Responses

  1. Spencer Cook

    I think these simple observations are overlooked by sooooo many fly fisherman. It is crazy how simple figuring out bugs can be. So is behavioral drift something that only mayflies do? I have only heard it discussed briefly some some experts. There are a lot of interesting ideas out there.

  2. Phil

    As far as I know Spencer, mayflies are the most significant behavioral drifters… I do know that some caddis also drift behaviorally at times if overcrowding is an issue to simply disperse. Plecoptera drift rarely if ever from what I understand. Most of your bigger stones (excluding Pteronarcys, salmonflies) are predators that crawl all over rocks simply gobbling up smaller inverts… Large strong legs = easy dispersion by crawling. Also, no need to run when you are the big dog.

    • Paul

      I believe that all aquatic invertebrates are affected by the drift. Just as fine sediment, rocks (both large and small) and other debris that are found in rivers. This is why all hatching insects migrate up rivers to lay their eggs and re-populate the system (i.e. Salmonflies).

  3. Brandon Scott

    Thanks this is great! I started following your blog last summer after I bought a beginner rig. I have loved the stories and great photos! This however is what I NEED, Subsurface is a mystery to me thanks for the insight!


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