Black and brown leeches. Tied on lightly weighted, but smaller (#12-4x thin wire) hooks. A marabou composition, with just a couple of folded wraps at the eye to give it a slightly thicker profile. No flash. When fished in the slow current, retrieval is a medium fast hand twist.
It then comes alive, wriggling its way through the water back to you, unless attacked along its way.
I had the good fortune several weeks ago to witness this natural (a real leech) attempting to make it to a destination under a clump of overhanging weeds, and, to be honest, I was amazed at (1) the shape, and (2) its ability to navigate through the water column, until it was intercepted, by a large rainbow just before reaching safe haven.
Having nothing even remotely close to resembling that in my boxes and film canisters, I fumbled about, and dug out the closest imitation I had. A bunny-strip leech. I submerged it, squeezing it until it was soaked, and dragged it through the water, observing. I was not thrilled with what I saw. My leech looked like 3 or 4 real leeches glued together. But, since it was all I had, it was given a chance to perform. Several, in fact. And then it was cut off, discarded, and I went back to what I'd originally been fishing.
About an hour later, 2 gentlemen set up nearby, and immediately each was on a fish. This event repeated itself several times in the following hour as my level of frustration crept higher and higher. Finally, able to cope no more, I reeled in, and set out for points downstream or anywhere away from this area. On my way past the second, I sought information.
"Black leech?" I queried, as he nodded in my direction.
"Brown one, actually", he replied. " Lost all my black ones earlier."
"Rabbit strips?" I probed.
So my observation had lead me to the right conclusion. Funny, for as much as I have fished there, how long it took me to finally attain visible proof of the details of a food source so highly prized by these trout. A protein payload. I'd captured scuds, chironomids, sowbugs, BWO and damsel nymphs, but had never had the opportunity to view one of the primary food sources available, and when I did, it was a real awakening. Oh, I'd have tied some anyway after seeing it, but having those gentlemen there underlining it the way they did sure put an exclamation point at the end of this particular sequence.
On my next visit, which was 2 weeks to the day later, I came armed with my usual box full of area-specific flies, and a collection of newly-tied marabou leeches. The day was overcast, threatening rain, with a rather langorous breeze slowly gaining strength out of the southwest. I looked at my 4-weight and grabbed the 5. More pop into the wind if I needed it, especially with the leech.
Anyway, it didn't take long. I went straight to my usual starting point, stripped line from the Evolution, and cast, across and a bit downstream. Here, the current was very gentle, allowing my lightly weighted leech ample sink time as it traveled slowly downstream. I think I got about 4, maybe 5 slow handtwists completed when there was a strong pull. The rod bent, and then recoiled. Then nothing. but,as I've learned from countless similar experiences, I continued retrieving maybe 3, or 4 more. This time the pull was fierce, and he was hooked. So was I. Tight to a fresh one with my new weapon, and grinning like an idiot.