Hidden hatches...how do you find them?

The Savage River like many great wild trout streams can be very frustrating especially when there is no apparent hatches. We are in kind of a lull hatch wise with many different bugs on the water little BWOs, crane flies, caddis, and a few slate drakes, but none of them in appreciable numbers that would indicate the fish are keying in on any one insect. What I do in these situations is start a process of elimination to try and find what the fish are eating. It is not a true guessing game because I fish with what I see flying around. One thing that I did notice was that only little fish were rising meaning that something is keeping the bigger fish under the surface. I can at least eliminate dry flies from my choices now where in the water column are the fish feeding? When prospecting with nymphs I divide the water column into three sections the bottom, middle, and just under the surface film. You can easily determine if fish are feeding just under the surface by observation. These fish can usually be seen and sometimes look like they are porpoising out of the water (they look like what dolphins do when the swim near the surface). I didn't see any of this, so I focused on the bottom and middle of the water column. After a couple of fly changes, I tied on a size 22 rs2 to see if the fish where eating BWOs and after numerous cast had yielded nothing I was about to change flies when I got a strike and lucky for me it was a nice 13 inch rainbow that was big enough to pump. When I pumped the stomach what I found was surprising. The trout was filled with size 20 caddis emergers. There were small tanish grey caddis flying around but nothing that would lead me to believe the amount that this fish had in its stomach. I switched to the appropriate fly and had an incredible morning of fishing. I got most of it on video, but did not realize the lens had fogged up after I got some awesome underwater footage. Oh well at least you can enjoy this video check it out!