randyflycaster,

Just had another thought on your question which may or may not explain the "how and why" I fish the way I do. I do not just cast the fly out there and hope to catch a fish. I "fish the fly" and fish it hard. I try to visualize where I feel the fish are holding and try to get my fly down to them because they may not come up for the fly. In moving water, the "better" fish will hold closer to the bottom where the current is not moving as fast as the current towards the top and they will not have to work as hard to hold their position. Fish seem to hold down close to the bottom at the beginning of a hole waiting for the food to come to them. This food, at the beginning of the hole, will be closer to the bottom because the riffle at the beginning of the hole will be driving the food down towards the bottom. Fish will also hold closer to the bottom at the end of the hole because their food will be coming up the incline to the riffles at the end of the hole. I hope this makes sense. I feel most fish and food will stay closer to the bottom due to the water current is slower than the current at the top. This is why I try to get my flies down as deep as possible where I feel they will present a more natural presentation. This "hugging the bottom" technique will cause you to lose more flies due to hang ups but the rewards are great. I guess that is why I tie my own flies instead of purchasing them. Kinda keeps the cost of flies down plus, when you tie your own, you will not be afraid of losing a few since you will have more and can replace the lost ones when you get home. So, mending a lot on the upstream cast puts the fly down deeper at the beginning of the cast and keeps it down there through the drift plus makes the fly stay closer to the bottom as it comes up the incline at the end of the hole. When I am fishing a very fast shallow seam, I will use a "high stick" technique and hold as much of the fly line out of the water as possible through the drift. When you give some thoughts to "high sticking", it is very similiar to the constant mending on the upstream cast because in both techniques you are trying to keep the floating fly line from pulling your leader and fly up.