Dave, Here is my two cents on the topic.
Having fished with a lot of fisherman of different skill levels over the years, I am convinced that three things really determine ones ability to figuire out the water. 1. As Kevin mentioned, understanding the food base in the stream is vital. It doesn't do much good to fish a Stone fly nymph in waters that don't have Stone flys for example though you would probably still get hits. I have never been one to use the screen but I know it works well. Especially when you are learning to identify the various nymphs. I tend to turn over rocks and observe what is swimming in the shallows and what is coming off the water. Both can be effective and I should probably combine the two for maximum effectiveness. A trip to the local fly shop can yield info on the regional patterns that work well too. 2. The ability to read the water and determine where the fish are is one of the areas I see a lot of fly fishermen lacking in. Most have the basics riffle, pool, tail concept down but they pass up a lot of pocket water. I know a river in B.C. that I fish and people are just starting to float it a bit. There is a hole that I hike back into that every floater I have observed has gone right over without stopping. That hole produces the biggest fish on that stretch of river! If they took time to look they would see the color difference in the water that denotes a deeper hole and notice that the current seams provide a perfect conveyor belt of food right by there. Another point to illustrate this concept is that I have just started fishing the St. Joe quite a bit the last two years. I have taken a couple of friends who have fly fished for years but put on foreign water, they just try to cover a lot of water to find the fish. A road runs along much of the St. Joe and you can see the river most of the way. One day I stopped at a long straight stretch. They asked why I was stopping here and I showed them the various pocket water, runs and log jams present in this stretch. All they saw was a straight stretch of water that didn't look very productive. We ended up having a blast in that stretch and hooked into a lot of fish. They are find fishermen but they haven't learned to really read the water. 3. Presentation is the third key. You can have all the right flys and local knowledge but if you don't serve it up right then you won't be as successful. I mentioned reading the current seams above. That is one of my primary presentation considerations. Can I get the fly to drift naturally by the hole. Sure you can plop the fly right behind the rock but rarely do the big ones come up. Drift it in the normal current seam and you will usualy get some strikes. On more open water it becomes a bit more difficult but finding what I call the dirty water is the ticket. You want the fly floating in that seam that isn't in the fast water but isn't in the super slow back pools either. Sometimes this seam is only inches wide but the fish respond well in this area. If the fish aren't taking the fly on the dead drift, mix it up a little. Try learning at what point in your downstream drift you can skate your fly on top of the surface. The takes on this type of presentation are incredible and it is often the big fish that hit. Also try letting your fly drag for half a second and then jerk it under the surface and proceed to strip it down and across from you. You will be amazed how many fish you can take this way. I may take some heat for this one as it is against everything taught by the book but it produces really well for me, especially with stone fly's. Finally, double your presentation by using a dropper system. On top use a dry that is easy to see and common on almost any water like an Elk Hair Caddis. Tie another piece of leader off the bend in the hook and use a bead head Prince Nymph or other nymph that imitates a lot of different insects (Golden Ribbed Hares Ear or Zug Bugs are two other good choices.) Now you are covering the surface and nymphing all at the same time. The fish will quickly show which level they are feeding at. Sorry about the dissertation.... I get carried away sometime, LOL. Mike W. Spangle
