Fly fishing a stream is unique in that there are many factors that go into success. Water conditions, temperatures, fly choice and so on all come to mind. One of the more basic issues is the contrast of dark and light on the water. Specifically, fish have a thing about the light from above.
In general, fish avoid areas of water exposed to the sun. Yes, you can find them in a sunny part of a stream or river, but they prefer to swim in the shadows. The simple reason is they are more visible in the areas of water exposed to the sun. Since most fish predators are coming from above, evolution has taught the fish that the sunny areas are dangerous areas. When the fish do stray into the sun, they tend to stay deep since birds have difficulty diving deep.
When looking for fishing spots, try to stick to the shadows. This is typically along the shore with over grown foliage. Other optimal areas can be under trees, rocks or banks along the shore. If you take the time to look around, you will start to see unique spots that offer excellent prospects. As you might guess, early morning and late afternoon are also excellent times to cast given the fact the light tends to dim.
Regardless of the above, there is one area where you should always avoid shadows when casting. No, you will not see them when sizing up the shoreline. Instead, you need to look at your feet. Yep, your own shadow. When on the shoreline or water, you need to control the direction of your shadow. If you are fishing in overgrown vegetation off the shore, your shadow cannot fall across it. If this occurs, the fish are going to associate it with a moving predator such as a bear or, in the case of smarter fish, humans!
When you head out for a bit of fly fishing, take note of the light. Understand it and you will do well. Misunderstand it and, ironically, you will end up in the dark.
