Fishing THE Foam.
MOST EXPERIENCED FLY FISHERS know that a line of foam floating down a stream tells them something about the location of trout. Unfortunately, that's usually about as far as their knowledge goes. That's too bad, because if anglers learn to recognize and read foam lines and foam mats, they can find more fish and make more effective presentations.
Here's an example of how it works. Jackson Streit and I fished the upper reaches of Colorado's South Platte River in the high, broad valley known as South Park. It's mostly meadow water in South Park, and except for a fine late-summer/fall run of brown trout out of Spinney Mountain Reservoir, the river holds few large fish. But, there is a resident population of browns in the 10- to 14-inch range, and they have a soft spot for dry flies.
We walked the river for a while, watching closely for risers, but no fish showed. Eventually, we came to a clump of grass that had fallen off the bank and stuck out into the current. A barely perceptible ripple and current seam formed off the point of grass. It was flecked with foam. Jackson touched my arm and quietly said, "Here." I knew what he meant.
I had a #12 grasshopper imitation on my line. This was, after all, meadow water with high grass, grasshoppers, and predictable winds that blew the bugs into the river. Jackson pointed at the foam line, and I cast quartering upstream to just below the grass clump. The hopper didn't drift a foot before a chunky 11-inch brown slashed it.
"It never fails," Jackson exclaimed. "We don't need risers. Where there's foam, there's fish!"
What is Foam?
FLY FISHERS SEE FOAM on the water's surface all the time. It's often caused naturally by decaying plant matter that adds tannins and lignin to the water. In rivers and streams, it collects in lines in slower currents. Large mats or rafts form when foam collects in eddies, swirls, and backwaters, and in lakes the wind creates foam that forms in lines and mats.
Get in Line
THE TROUT IN MY EXAMPLE was there because the clump of grass that had fallen into the current created a seam between the fast water in the main current and the slow water downstream of the grass. Trout gather along these seams to feed on drifting foods that become trapped in the water that wells up where the two currents meet. It's a trout cafeteria line and the foam on the surface outlines its location. If you're into reading the water, the line of foam is like an important underlined sentence.
Fish that linger in the foam line to feed seldom step out of line to eat a natural, or your fly. They usually hold in a narrow lane under the foam line, but sometimes, if many bugs wash into the calm water behind the main current, they may feed there randomly or methodically. It's as if the trout go from table to table, picking up leftovers after they've been through the main line.
If the fish are in a lane under the foam line, present your fly at the head of the foam line so it drifts naturally with the foam. Watch the foam for signs of microdrag (unseen) on your fly.
Where you position yourself around the foam line or mat (the two often occur together) will determine the best presentation tactic. There are many options, but seven casting positions and presentations cover most situations (see illustration on previous page).
Glides and Flats
IN ANOTHER SCENARIO, consider a line of foam coursing through an otherwise featureless glide or meandering through a featureless flat. The foam line gives you a general guide to where the main current flows and where the channel is. Fish both sides and down the middle of the foam line. A well-defined channel may also have a ripple line. On a flat, the channel may be as little as six inches deeper than the surrounding area, but it's enough to attract trout.
Trout hang around channels because the slight difference in current velocities along the channel might kick food out of the main current. Also, the deeper channel water provides cover and food. Trout often hold along the channel's edges where the streambed slopes into the channel. The surface foam highlights the current that carries subsurface food to trout.
It doesn't stop there, either. You can bet that when a hatch comes off, no matter what the insect species, bugs that spend much time on the water's surface emerging from their nymphal or pupal shucks will float downstream and get caught in a foam line. The foam line shows you exactly where to find the trout chow line. Use it as a guide to position yourself for the most productive drag-free drift, and you'll hook more trout.
Under the Mat
FOAM MATS ARE LARGER, more contiguous foam formations. A foam mat is almost always found in dead water, backwaters, swirls, or eddies. The mat forms when lines of foam floating downstream become trapped together and are unable to return to the main flow. As more and more foam is trapped, the mats become larger and more dense until high water or wind breaks them apart and moves them back into the current. Foam mats can be as small as one square foot or as large as 15 or 20 square feet, or larger.
The mats attract trout for several reasons. They provide excellent cover, where a fish can stay close to the water's surface but remain undetected. In backwaters, eddies, and swirls, one edge of the foam mat lies typically along a seam or foam line that can be a food line. Trout often lie under the mat, positioned near the surface, and ease out toward the main flow to pick off subsurface foods that drift by (similar to an undercut bank). Sometimes food becomes trapped in the foam, where it is easy pickings.
I once saw three trout rising methodically along the edge of a large foam mat on the Colorado River. There was a Trico spinner fall in progress upstream, and these fish were picking spent spinners out of the foam. The foam is sticky enough to trap insects as large as grasshoppers, so a trout stationed under a foam mat can usually find something to eat. It's a sweet deal for the fish, and in my experience, the largest trout in a section of stream often occupy this prime water.
Strategies for Foam Mats
THE TACTICS USED TO CATCH trout in foam mats are not unusual; however, success around foam mats can require innovative twists of standard strategies.
If you see trout moving out from under a foam mat to take either subsurface or surface foods, use a standard nymphing or dry-fly tactic. The trick is to figure out the drift and get the fly as close as possible to the edge of the mat. During a hatch or spinner fall, try to time the feeding rhythm of the trout as it moves back and forth from under the mat. Present your fly so that you set the table for the fish just when it's ready to emerge for a bite.
When trout pick flies out of the edge of the mat or feed under the mat, you may be able to place a dry with a pile, slack-line, or reach cast so that it sticks in the foam at the edge of the mat for a moment--long enough to induce a take. You can enhance the presentation by casting down-and-across-stream so that the fly bumps along the foam edge or gets embedded in it momentarily.
A drag-free presentation made across the main current to a foam mat on the far side of a seam can be an especially difficult challenge, depending on how fast the water moves. You can make a slack-line or reach cast, but a better tactic is to reposition yourself directly downstream from the foam and cast directly upstream to the inside of the seam. A slightly across-and-downstream presentation from the same side of the river as the foam can also put your fly inside the seam.
Flies cast into the edge of the mat are nearly invisible. So use parachute patterns when you cast drys at mats. I modify my parachute patterns by adding a bright, fluorescent-colored polypropylene or hair post. A parachute dun can be trimmed to imitate a fallen dun, spinner, or a stuck-in-shuck emerger. If you're stumped on what the trout are eating, scoop a handful of foam and examine it for insects. Match the naturals' size and color.
What do you do when trout rise in the foam mat's interior? If the mat is thin, cast a parachute dun directly at the rising fish or to an opening in the foam near the fish. Casting accuracy and the brightly colored post are crucial. If the foam is so thick that the fly gets lost, set the hook when you see a slight bulge or any movement in the foam near your fly.
Trout in the middle of an eddy can face any direction or cruise in the relative calm of the swirl's interior. If the foam is broken, you may be able to pick a fish and work to its feeding idiosyncrasies, but more often you'll just have to cast the fly into the center of the eddy and hope the trout come to it before it drags.
Eddies that trap foam in the center can make dense foam mats that are a few inches high. Although the foam hides the circular eddy current, you may need to fish the mat using the same strategies that apply to eddies without dense foam, especially if you use nymphing tactics.
If a single dry fly won't entice a strike, try using a dropper. I prefer trailer flies like the Hare's-ear Soft Hackle because they imitate a wide range of aquatic insect life stages--nymphs, emergers, crippled adults, or drowned adults. Of course, if you can match the color and size of the prevailing naturals, do it. A bead-head nymph works well because it sinks beneath the foam. You can also attach weight to your tippet to sink the trailer through the foam, but remember that any presentation that disturbs the foam mat can also disturb the trout.
You want the dry fly to become embedded in the foam and the trailer to break through the foam and dangle underneath it. Use the dry as a strike indicator, and set the hook if it goes under. This is not easy to do if the eddy has a strong circular current, but it is effective in the calmer center of the eddy. Manage your fly line by holding it up off the current, or use a slack-line presentation to prevent the line from dragging the fly across the foam, which will put the trout down. If you put the fly on the foam properly, leave it there until it begins to drag. Trout cruising under the mat may take a few moments to find the suspended fly.
You can also use streamers to draw trout from under foam mats. Cast a streamer onto the foam mat, let it sink below the foam, and retrieve it to imitate a fleeing baitfish.
ALL FOAM MATS have two important ingredients that attract large trout-- hiding cover and access to food. Don't forget the simple adage, "Where there's foam, there's trout." As Norman Maclean noted in A River Runs Through It, the backeddies where the foam collects are the Lazy Susans of the trout's world.
ED ENGLE, author of Fly Fishing the Tailwaters, is FLY FISHERMAN'S Southwest Field Editor. He lives in Manitou Springs, Colorado.
Casting Positions & Presentations
CHOOSE ONE OF THE FOLLOWING casting positions to make dry-fly or nymph presentations to fish in different areas of a foam line or mat. You'll need to know how to make upstream, up-and-across, down-and-across, and down-stream presentations with reach, pile, and slack-line casts, and line mending techniques to avoid drag. [Information on these casts is available from many books and at the Virtual Flyshop, www.flyshop.com(Improving Your Skills) THE EDITOR.]
IF a fish refuses your fly before it drags, allow the line and fly to drift away from the foam before picking up carefully for another cast. If you disturb the foam, you'll disturb the fish. False-cast away from the foam to avoid sending line spray over the fish and putting them down.
1 Cast across (1a) or up-and-across (1b) with a reach, pile, or other slack-line cast to put the fly and tippet in the foam line, or along the foam mat and the leader and line in the faster current outside the foam line.
2 Make a down-and-across pile (2a) or reach (2b) cast to place the fly and leader in the foam line or on its outside edge. Shake line out of the rod tip to lengthen the drift.
3 Make a slack-line cast straight upstream to put the fly inside the foam line next to the foam mat. This is upstream fishing in a narrow lane.
4 Treat the bank side of the backeddy as a separate tiny stream flowing in the opposite direction as the main stream. Cast from an "upstream" position to present the fly to the fish without drag.
5 Make a downstream reach slack-line cast to put the fly and leader inside the current seam next to the foam mat. Put the line in a side current and feed out line for a longer drift, If a fish doesn't take, a sloppy pickup can spook it.
6 Cast directly to cruising or rising fish in the interior of the foam mat, or cast to the mixed currents in the center of the eddy and wait for a trout to take the fly before it drags. A slight twitch can induce a take.
7 Make a slack-line reach cast to place the fly on the inside edge of the foam line and the line in the calmer mat water. Retrieve and mend line to avoid drag as the fly drifts toward you.