Baetis & Caddis – Spring Dry Flies

As I’ve blogged about before, spring is one of my favorite times of the year to fly fish in our valley for a number of reasons. While every angler is different, few would argue that throwing a dry fly at rising fish is one of the most fun things you can do with a fly rod in hand. That’s certainly true for me, and perhaps the biggest reason I enjoy the spring so much here in the Roaring Fork Valley. So let’s talk about the most prominent hatches we see in the Spring and how you can have a blast throwing dries to eager fish!

Blue Winged Olives (Baetis)

Starting sometime in March, we begin to see our first true hatches of the year in the form of blue winged olives (also known as baetis). As the water temps start to come up and the days get longer, BWOs start to come off in large numbers. They especially like overcast days where the clouds roll in, which is great because it’s those conditions where trout are most likely to feel comfortable rising to bugs on the surface.

A beautiful rainbow trout caught in March during a BWO hatch

What time of day do they typically start hatching?

As you hopefully understand, bugs don’t wear watches and follow specific schedules. That said, if you’re on the water in March & April and hoping to fish a BWO hatch, the most likely time for them to start coming off in big enough numbers to warrant large numbers of rising fish is somewhere around 12 or 1 PM. Some hatches only last an hour, while other times they’ll come off in waves until the late afternoon. Again, your best bet are overcast days that aren’t too windy. If you hit it right, a feeding frenzy can occur that makes the water look like it’s boiling as fish after fish after fish rise to the bugs.

What flies should I use?

I’ve always felt like our spring baetis were about a size 17. With that said, what I usually do is tie on one #16 baetis fly and then trail it with a #18 baetis fly. Everybody has their favorite patterns, and truthfully I’m not sure it matters much what bug you use in the spring. The reality is the fish haven’t seen much pressure in awhile and they’re really hungry. A proximate imitation with the right presentation will usually elicit a take.



Oh boy…caddis, caddis, caddis. Perhaps one of the most prolific hatches we see all year in this area is what is known as the Mother’s Day Caddis hatch. If you haven’t put it together yet, it usually occurs some time around Mother’s Day. To put it bluntly, our rivers explode with millions of caddis larva hatching consistently during the mid-day hours, resulting in some truly epic hatches.

Generally speaking, you can expect these spring caddis to be around a size 16, and they typically have a darker body than some of our caddis hatches that occur later in the season.

What flies should I use?

I usually fish 2 dries at one time, much like with the olive set-up I mentioned above. My point fly is typically a dark bodied caddis imitation like a “never sink” caddis or a traditional deer hair caddis. Behind that, I usually tie on a ginger variant colored body that has a lower profile in the water and mimics a female caddis sitting on the water and laying her eggs.


A couple of notes…

Spring weather…to say that it’s unpredictable in the spring would be an understatement. As I type this, it’s April 17th and there are snow flurries outside with wind gusts above 50 MPH. Tomorrow the forecast is 60 degrees and sunny. There’s simple no telling what to expect if you’re planning a spring fly fishing trip in the Aspen area. I will warn you that it’s not uncommon for there to be quite a bit of wind during the spring which can make trying to throw small dry flies a challenge, to put it nicely.

Some times it’s not unusual for both olives and caddis hatches to occur at the same time. When this happens, fish tend to key in on one species of insect over another. You can either fish a double dry rig with one caddis and one baetis pattern, or you can try and decipher which insect they’re eating. One simple trick is to take note of how they are eating. When trout are eating caddis, the takes are typically splashier whereas when they are eating baetis they ‘sip’ the bugs off the surface. Caddis are much more active bugs in and on the water, so trout know they have to act quickly to eat them before they scurry off. Because of that, they’ll rise more quickly and create more of a splash on the surface. With olives, the takes can be tantalizingly slow and deliberate. So take a few minutes to see how the trout are eating and that will usually give you some indication of the best flies to throw at them.

My final note has more to do with a tip that you might find helpful when fishing an olive or caddis hatch in the spring (or any time for that matter you find yourself trying to catch “rising” fish). Often time inexperienced anglers see a fish ‘rise’ and assume that fish is rising to the surface and eating bugs off the top. In reality, what often happens is fish will be keyed in on emergent insects that are attempting to make it to the surface to dry out their wings so they can fly off and mate. If you notice a fish making a disturbance towards the surface, take a few minutes to watch the fish to see where it’s actually eating. If you see it’s mouth coming out of the water, that’s a clear indication it’s eating on the surface. But if upon closer inspection all you see is its back, that’s a sign it’s eating just below the surface. In these instances, you’ll want to fish a decent sized dry fly that floats well, but then below it (off the bend of the hook tie a 12-18″ section of tippet) fish an emerger pattern with a small amount of weight for whatever hatch is coming off. When doing this, you’re using the dry fly as your indicator, such that when it disappears under the water you know to set your hook as the fish has eaten the dropper fly that was floating just below the surface.

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