Bruce Ajari: Water boatmen often overlooked by fly fishermen
An often overlooked aquatic insect for fly fishermen is the water boatman (Corixidae). It grows to about a half inch. It is an oval-shaped insect, black or brown in color, and swims using the most distinguishing feature ” fringed, oar-like hind legs. Air for breathing is in a silvery film on the abdomen. This air is obtained by touching the thorax to the surface of water.
I am sure that we have all seen these insects. All you have to do is look into a slow-moving section of the stream, or explore a pond, lake or reservoir. The oar-like legs move them downward from the surface in a jerking fashion.
They eat minute plants and animals gathered with comb-like front tarsi. Most important to fly fishers is that they are found at all elevations, which means they are quite a food source for trout.
There are around 500 known species of water boatmen worldwide. The most common genus is Sigara and Cenocorixa found in the Sierra Nevada, which have a number of different species. As with many other insects, it is not important to know the exact species to imitate the insect as a trout food. He or she only needs to know the size, shape and coloration of the insect in order to get a reasonable imitation the trout will eat.
These aquatic insects can be found in some of the most unlikely places. Have you ever seen these in a swimming pool? How about a decorative pond or even a bucket of water? I have as a kid. While many say that water boatmen do not bite and are often confused with the backswimmer, I am sure that the insects in the pool were water boatmen, so I would urge some care in handling them if you come across them and want to take a closer look.
Most people do not know that these insects do in fact fly. This explains why you find them in so many places. I really did not know this until I first moved to Truckee. It was a fall day and I was just finishing putting on a good coat of wax to my truck. I heard a thud on my hood and turned to see a large water boatman spinning around on my car hood. Apparently, it mistook the reflection of my hood as that of a body of water.
In the fall there are some lakes in which it will actually look like it is raining on a clear, sunny day. What is actually happening is that the dimples are caused by water boatmen crashing into the pond like the one did on the hood of my truck. When this occurs, trout will really key in on them as a food source.
Spend some time watching the behavior of these insects the next time you are fishing on a lake or reservoir that has them. Then go ahead and try and imitate their movements with your fly pattern and do not be surprised if you have some great results.
I can still remember the first time I gave them a try in the fall at Davis Lake quite a long time ago. I was pleasantly surprised with the results, and you will be too.
Bruce Ajari is a Truckee resident and regular fishing columnist for the Sierra Sun and other area newspapers.
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