We have all had the experience of seeing and fishing a hatch it can be productive to fish but they only last so long. About 12 years ago I was doing some stream sampling for a water quality survey on a local river. I had fish there the day before and had gotten into a good Hendrickson hatch with some sized 18 blue winged olives mixed in. It had only lasted about an hour or so but the fish seemed to be active even for an early part of the year. When I did my kick surveys I found that about 60 to 70 % of the nymphs I picked up were of the two species that were to hatch later that day. I guess that is when the light went off and I have been fishing hatches “bottom to top “ever since. The next day I would fish the “Complete” hatch. Having studied aquatic bugs for some time I knew the type of water the nymphs would be living in so I put on a pheasant tail nymph size 18 and a larger brown colored nymph. I fished the heads of pools and the transition from riffles for about an hour and a half before the hatch was to happen. I did not make more than 3 drift when I hooked and landed a nice rainbow and managed a bunch more before the trout started to rise and key in on emergers.
Armed with a little bit of knowledge of the bugs to be hatching and type of water the nymphs inhabit can make for a good day. I now carry boxes with nymph, emerger, dun and spinner for most all the hatches. So if your on a favorite stream or even a new place try to find out if anything has been hatching and then try fishing from the bottom up.
One big thing to remember is that when nymphs are getting ready to hatch they are not some inanimate object just floating in the current they will move and swim to get to were they want to go. Some of the large stones will let go of the bottom and tumble into a pool to slower water and crawl to the bank. For year I tried to imitate them crawling along the bottom with little success. So I then changed my attention to the point at which they are tumbling thus the “Riffle stone” pattern was born and boy it can be a killer at times. So just don’t sit around a wait for the hatch to begin fish the unseen hatch below.