The Fishing Bug

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Published on: Mar. 2, 2004

Last revision: Nov. 16, 2010

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

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