Just because you might be sacrificing space and stability in a canoe, you don't have to give up helpful modern technology. You could consider adding a fish finder to the side of your canoe.
These handy tools work by using sonar -- a technology developed for the purpose of detecting enemy submarines in war. Essentially, the technique involves emitting sound waves underwater and measuring the echo response. A transducer clamps to the bottom of the boat and sends information to the display on the boat.
It can be easy to rely too heavily on a fish finder device instead of enjoying yourself or even using other effective, time-tested techniques. But if used well, the fish finder can help you bring back a bigger haul. Keep in mind that good fish finders tell you a lot more information than just the location of fish. They can measure the temperature of the water and depth levels, and provide other details about the bottom. So, using your knowledge of fish behavior and preferred locations, the fish finder will help you scout out the best locations for casting a fly.
Fish finders come in many shapes and sizes (as well as costs). For a canoe, find a compact model with a display that clamps to the side of your boat. You'll also need one with a transducer that easily slips out of its clamp so you can take it out in shallow water [source: Mitchell].