Let’s Talk Bugs
by Tom Lager

Saturday as I walked along the Peshtigo River to one of my favorite salmon fishing spots, I noticed how extensively summer has given way to autumn. The asters had only a few heads of purple left, ferns were dried, aspen leaves blanketed the trail and floated down the river driven by a sharp wind. The whole terrestrial landscape was in transition toward dormancy, a time of slow down and completion of natural events.

Not so for the aquatic landscape. Although at first look, the riffle I fish from appeared stark as a strong steady flow swept over the rocks and cobble. But what were not readily evident were the hundreds of thousands of new lives underway. Fall is a time of abundant growth for bugs and the renewal of life for the fall salmonid spawners. Picking up rocks and gravel, especially those partially buried in the river bed reveals the harbor for tiny insects - mayflies, stoneflies, caddisflies and midges. Yes, occasionally you will see the large stoneflies and dragonflies that take several years to mature; but by sheer numbers these new lives dominate the biomass of fall.

A key stimulus for this growth comes from the dormant terrestrial habitat in the form of leaves. Leaves entering the streams and rivers become entrained in the currents, saturated with water and gather on obstacles and in the crevices among rocks. The sugars within the leaves attract bacteria and fungi which colonized the surfaces of the leaves preparing them to be shredded by insects that consume both the bacteria / fungi community and the leaf. There is tremendous activity here, we just have to know where and how to look. To me this is awesome creativity on His part… the poet John Gray wrote:

“Mark well the various seasons of the year, How the succeeding insect race appear; In the revolving moon one colour reigns, Which in the next the fickle trout disdains.”

Speaking of fish, on queue, the salmon are on the riffle. The wakes disclose their maneuvers. I carefully swing a chartreuse winged Barteau Minneaux that drifts through the pool above the riffle; now it races downstream and I set the hook. In a matter of minute-parts backing is whipping off the reel - the disk brake is applying a steady stress as the rod bounces to the rhythm of the run. Tail-walking is managed, another run across river is made and a stubborn tug-of-war pursues. The rod is bent in a strong arch and the wind wines across the taught backing like a cellist’s bow across strings. This is the “tune of pure pleasure” and exhilaration! I forget the sharpness of the wind and work the salmon back to the riffle cautiously maintaining tension during more tail-walking and cross river drives, until it is over and salmon and fisher are free - released to our respective stations.

It is amazing how “bugs” enable these emotional encounters. In this case it has been the bugs or invertebrates called Mysis relicta in the Great Lakes that provide for the salmon. Between casts, take the time to maintain and enhance your knowledge of bugs by turning rocks and peaking under to see who is looking back at you.

Now that we are out of the small inland streams for most of the autumn and winter, what is going on there? It is a time for renewal for many insects. They have either hatched from their eggs in late summer or early fall and are now growing to eventually be the food of trout – not that it is their plan to be eaten, but we know what trout like. In order for the bugs to grow they need energy and calories just like we do. The greatest source of energy, in small streams, this time of year comes from leaves that fall into the stream.

This is especially true for small streams like the upper reaches of the Thunder and Pine rivers. I had the pleasure of catching many brook trout there over this last summer. These small headwater areas are being recharged with energy from the leaves, as we speak. The leaves fall or are wind blown into streams and accumulate in pools, around and under logs. From a “bug’s” point of view this is great. Actually, it is just like eating peanut butter and jelly on crackers. Well that may sound far fetched – but in reality it is not. You see, as leaves fall into the streams, the sugars within the leaves attract bacteria and fungus to grow on their surfaces, forming a layer of protein and “carbs”. This layer is like the peanut butter and jelly on a cracker; the bugs go after the good stuff on top as they eat cracker. Fortunately for us and trout, bugs don’t worry about the “carbs” - more “carbs” mean more bugs, then more trout and more trout mean … I think you know what that means.

This type of bug is referred to as a shredder, they shredder the leaves and break them down into smaller organic particles. Good examples of this are the Limnephilid caddisflies, that crawl along the stream bottoms in the “stick-like” cases they construct. Also the giant black stoneflies like Pteronarcids and some smaller ones as well are shredders. The small midge larvae also get involved.

So this fall as you hunt grouse, deer or just go out to enjoy the colors of autumn and fresh scents of fall, be aware of the transformations that are occurring. Those beautiful colors are soon to be transformed by the bugs into trout food throughout the fall and winter, while the streams prepare for our return in the spring.