All good trout rivers are full of rocks. Bankside and midstream, big ones and small ones — rocks are everywhere. Unless the bottom is gravel or sand for long stretches, the composition of the riverbed is a series of boulders and stones scattered in various sizes. Trout thrive in these places because rocks create structure and current seams. That structure offers protection, while the seams provide feeding lanes. And to the fisherman, those lanes are everything.
Downstream of every rock are three obvious seams: the left seam, right seam and the slower seam in the middle. That part is easy. But the most productive seams are more hidden, and many anglers seem to miss them altogether. These are the two merger seams, where each fast seam meets the slower part in the middle. And if I had to pick just one target area, day after day and season after season, I would surely choose the merger seams.
Anywhere faster water meets slower water is a merger point. The old adage that foam is home applies here, as merger seams certainly are the collecting point for those bubble lines. But only a small percentage of merger seams form bubbles, and the attentive angler finds merger seams behind literally every rock.
The merger seams behind every rock are easy to find. Look for the three main seams: fast left, fast right and slow center. Now find where the slow water meets the fast water, and treat those two strips of water as their own seams. These are the mergers.
Most often, merger seams are narrow strips, from just a few inches wide to twelve inches or better. Sometimes these lanes are ten or twenty feet in length and easy to follow, and other times the merger is very short — just a foot or two — before it blends in with the neighboring seam or is overtaken by the next lane. But the mergers are there, and trout know it. Fish sit with their bellies on the bottom of these seams, because they have the best of everything — softer water to sit in, and food drifting by. Often, that food is concentrated in a skinny seam and drifting directly to the waiting trout.
Anglers of all types quickly understand that accuracy is imperative if any consistent success is to follow. So most beginners develop the necessary skills to place the fly in an area. But the next-level angler continues to refine that accuracy until true precision is achieved. The first goal is to fish all three main seams that are downstream of a rock (left, right and center). And a step beyond that is to target the merger seams. That’s hard, because the fly and tippet must cooperate enough to hold a narrow strip of water without drifting into the neighboring seam, fast or slow (assuming the goal is a dead drift).
Such skill comes with time and persistence. But the payoff can be extraordinary. Suddenly, a pocket that produced nothing with an area-approach can turn up a handful of fish with a tediously targeted multi-seam approach — especially when focusing on the mergers.
Pocket Water Advantage
An abundance of rocks combined with a high gradient creates a fisherman’s favorite — pocket water. And whether I’m fishing dry flies, nymphs or streamers, I’ll choose the broken pocket water every time I’m given the chance.
With endless seams and oxygenated water, boulder strewn runs are the food factories of a river. Add in the extra cover and the fact that many anglers avoid the challenge of such places, and pocket water is the perfect chance to catch a pile of trout.
Mixed into every stretch of pocket water are countless lanes that mix and blend with each other. And downstream of every rock are five seams — not just three. Fish the mergers. Find the trout.
Fish hard, friends.
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Enjoy the day.
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