The Fishing Bug

By | March 2, 2004
From Missouri Conservationist: Mar 2004

Standing knee deep in the Gasconade River trying to decide what fly to tie on to my line, I was startled by the nearby splash of a feeding smallmouth.Soon, I started spotting lots of floating mayflies, and fish began rising regularly around me to sip them from the surface.

After identifying the specific mayfly hatching, I tied on a #12 Mahogany Quill dry fly to my leader. The artificial dry fly was the closest match I could make to the Isonychia bicolor mayflies the fish were eating.

I picked out a rising fish and cast to it. The fly landed about 4 feet upstream from where the fish had splashed and drifted into the feeding lane. Water and flashes of bronze erupted as a smallmouth attacked the fly. The fight was on. My reel buzzed as fly line stripped from the spool. When I finally landed the fish, I held it up and admired it, before releasing it. My imitation had worked. Smallmouth bass are suckers for mayflies.

The Isonychia bicolor mayfly lives among the rocks at the bottom of streams. The I. bicolor, like all of Missouri's mayflies, is an invertebrate. It has no backbone. Since it can be seen without a magnifier, it is considered a macro-invertebrate.

I. bicolor remains at the bottom of the stream in its nymph al stage for a year. As the nymphal stage nears completion, the nymph swims to the surface of the water, and a transformation takes place. When the mayfly reaches the surface of the stream, its exoskeleton cracks open much like a cocoon.

The winged subimago (young adult) struggles to free itself from its final aquatic nymphal shuck. It then sits quietly on the surface of the water drying its wings before taking its first flight, which will take it upstream to mate. It is at this point that the insect is most vulnerable to fish.

When I started tying flies 37 years ago, I had no idea that mayflies and smallmouth bass often occupied the same stretches of streams because they had similar needs. Most Missouri mayflies are very sensitive to organic pollutants and require high oxygen levels. Smallmouth bass also do best in clean water with high levels of oxygen. Both the insect and the fish that eats it require the same environmental conditions.

That's why the upper reaches of the Gasconade provide such good smallmouth bass fishing. The headwaters of the Gasconade River are in mostly rural areas in the Ozarks. Cattle farming and some row cropping contribute only a small amount of nutrients, pesticides and herbicides to the stream. Even though the Gasconade is one of Missouri's longer streams, it doesn't flow through any major municipalities and is not impacted by municipal water treatment plants.

If you spend much time wading rivers and streams looking under rocks, you'll soon learn that water quality and insect populations are usually connected. In some streams, you won't find a mayfly nymph, nor will you find a stonefly nymph or a caddis fly larva. These bugs are sensitive to pollutants and will not live in a stream that has a history of pollution.

A successful fly fisher understands the relationship between the insects represented on a hook, the fish, and the condition of the stream or water body he or she is fishing. The next time you visit a new stream or an old favorite, walk out into a riffle and look at the bottom of some of the rocks.

If all you find in your stream are pollution-tolerant insects like aquatic worms, leeches and black fly larva, it is likely that fishing won't be good. The absence of the sensitive species and the presence of only the tolerant species indicates long-term exposure to pollution. Sensitive macro-invertebrates mean clean water and healthy fish populations.

Leeches, aquatic worms and black flies also may live in clean, unpolluted water, and there are some excellent fly tying patterns for these creatures. However, a healthy aquatic ecosystem should harbor a diversity of macroinvertebrates, including the sensitive ones.

Some streams are polluted by lagoon spills, leaking septic systems or myriad other pollution sources. If the problems are intermittent, the stream might still be healthy enough to support macro-invertebrates that are somewhat tolerant of disturbances. You may find crayfish, or sow bugs, or those wild and crazy, side-swimming scuds.

Fortunately, there are patterns in fly tying books for all of them. It is good to be able to identify various macro-invertebrates like the mayflies, caddis flies, and stoneflies. Until you can identify them, look in your fly tying pattern book and try to match the insect you see in size, color and shape.

How to stock a fly box.

When you sit down at your fly tying station, you should try to imitate what you saw on your last trip to the stream. Carrying a journal on the stream is a good idea for jotting down important tidbits of information like the color and size of the insects,the weather conditions and the time of year. Journals are also a great way to relive fantastic fishing adventures.

Pick it up--Pack it out

If you enjoy fishing, you probably already know how important it is to keep our streams clean and healthy. Everyone should pack out their own trash, but it's also helpful to pick up trash that others may have left behind.

Become an official caretaker of a section of your favorite fishing stream by joining the Missouri Stream Team program. Find out more about the Stream Team program online or call (800) 781-1989.

This Issue's Staff

Editor - Tom Cwynar
Managing Editor - Bryan Hendricks
Art Director - Ara Clark
Artist - Dave Besenger
Artist - Mark Raithel
Photographer - Jim Rathert
Photographer - Cliff White
Staff Writer - Jim Low
Staff Writer - Joan McKee
Circulation - Laura Scheuler