I woke up thinking I may have my first day of dry fly fishing in 2024. Two different friends reported hatches in the same week. A combination of moderate sized (14-16) brown stoneflies and small black stoneflies (18-22) were emerging from the river and inducing surface feeding from wild brown trout. Fishing dry flies for surface feeding fish is about as good as it gets for a fly angler. After back-to-back skunks, I felt like I was due an excellent afternoon on the river. 

Optimism filled me as I strung up my dry fly rod and tied on a black dry fly that could pass as a stonefly but was first imagined as a caddis fly. At 1:37 pm, I finished tying the laces of my wading boots. I was ready. I was focused and full of hope. 

Based on my friends’ reports, 2-3:30 pm was the likely window for the hatch. Wind had come overnight, and air temperatures had dropped a few degrees from previous days. Outside of the chilling gusts of wind, the air temperature felt close enough to previous days that I felt positive I too would be experiencing my first dry fly fishing of the year. 

Casting a dry fly on a fly line felt soothing and refreshing, reminding me of the first days of spring. There is something about feeling the line on my fingertips that is more satisfying than holding the mono-rig I typically use. It has been quite some time since I have cast a dry fly and I am thankful I have a few minutes to practice before I anticipate the hatch and feeding frenzy will occur. 

A Warm Winter Day on the River

I practiced different aerial mends, preparing for different water conditions and required presentations. Gary Borger’s book Presentation is fresh in my mind. While the explanations are clear, my skills are far from precise, but I manage to refresh my “reach” mends to allow myself to build slack to the right and left of my casts. Multiple currents across the stream can quickly pull a dry fly into an unnatural movement. Introducing some slack into the line allows for additional time for a fly to float drag free, before the line tightens. Within 20-30 minutes I had regained some accuracy and control over my casts and dry fly presentations. Now I was really ready. 

I scanned upstream, intently staring at the water surface, looking for any disturbance near a large boulder or fallen tree. On the glass and smooth surface, the rings of a rise would be relatively easy to spot, but all I saw was the reflections from swaying trees. My eyes moved from the water to the air, trying to find fluttering insects. Another gust of wind rattles the branches in the trees overhead, breaking my stare. No insects appear in the air or on the water. 

Over an hour into my vigil nothing has changed but my confidence. I make my way upstream, hoping a change in scenery reveals a change in conditions. I know that emergences of insects can migrate upstream and optimal conditions are generated for the broods. No such luck. 

Around 3:15, I resigned myself to the idea that today will not be my first dry fly catch of 2024, but the water looks deep, clear and fishy. Time to change things up. Changing my rig to add two nymphs, I notice several rocks near my feet covered in tiny bubbles. The nerd in me cannot resist hypothesizing potential causes. I ran through as many memories as I could muster of similar accumulations of bubbles. All my recollections included periods of time when ice was on the water. My guess is that water temperature was increasing through the day and the ability of oxygen to stay dissolved was decreasing, forming bubbles that eventually are released to the air.     

Bubbles gathered on the cobbles

After 20 minutes fishing with nymphs under an indicator through the slower, deeper water, I hooked and landed a nice brown. I was relieved the skunk was over. As the sun fell behind the trees, I packed up and headed to the truck. Why did the stoneflies hatch two days ago, but today were nowhere to be seen?

Skunk breaking brown trout

I looked up the stream gage and found temperature data for the previous days. Low temperatures generally occurred around 6:30 am and high temperatures were almost uniformly at 4pm. On the day of the confirmed hatch the low temperature was 37.6 degrees Fahrenheit, and the high was 42.1. Later in the evening, I checked back to see the temperatures when I was on the river, 37.8 and 42.8 were the low and high temperatures, respectively. The day in between, temperatures were 37.0 and 41.7. So, if water temperature is the trigger for aquatic insect metamorphosis, is one degree enough to shut off a hatch? Or did all the brood emerge in the days before I was there?

There is always something to learn on the stream. Being present in the moment can help you focus on collecting data and solving the puzzle in front of you, but sometimes you need more data, to understand history, or you need to change your perspective. Evaluating hatches is a part of fly fishing I would like to know a lot more about. Looks like I need to track more data and spend more time on the river! I recognize there are things about life in a stream I may never understand, but it sure is fun to try.

Keep Mending…     

One Reply to “What Does It Take for An Insect to Hatch?”

  1. I am surprised insects hatch during these winter days! How long is their life span?
    I like the part of the bubbles!
    So much to learn!

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