Small Stream Structure- Woody Debris and Other External Features

1 comment / Posted on / by

Photo by Louis Cahill

By Jason Tucker

Wood is good!

In the two previous installments I’ve discussed fluvial stream structures (holes, runs etc.) and substrate types. If a stream were a house, then the substrate would be the foundation and floors, fluvial structures would be the walls and rooms, and the woody debris and other structure would be the cabinets and furniture. If that helps. Understanding woody debris, and how it relates to the other features is key to your fishing success. The geography of where you’re fishing greatly affects its importance and utility to the fish. In Appalachian mountain streams a lot of woody debris simply gets swept away or pushed to the margins in slack water; in northern trout streams it is very important.

Woody debris. Trout use woody debris for structure and cover. It also provides homes and food for a lot of aquatic insects and is part of the basis for life in a stream. Don’t underestimate the power of woody debris to create fishing situations. Logs lodge across the currents and create pour-overs. Those pour-overs then create holes. Conversely, logs can lodge higher in the water column, forcing the current down and routing out the bottom. That also funnels food into the spot, a double whammy of food and shelter. 

Brush piles and log jams. Brush piles and log jams are trout hotels and provide vital escape cover from predators. As far as fishing goes they are some of the least interesting features in a stream to me. Look for fish to move out from them to feed on hatching insects. You can often tempt hiding fish into striking a streamer around the edges, and look for trout feeding on surface flies right on the leading edge where the current is sweeping insects into the wood. It’s a tricky spot to fish, and even trickier if you hook up. Be ready to put the cork to any fish you hook up on near wood. 

Individual logs. Here I’m talking about logs parallel to the current. Trout love these, especially if it’s slightly undercut or has a deeper channel next to it, whether it is fully submerged or breaks the surface. Try to spot submerged logs far enough away without disturbing fish. They’re great places for picking off individual fish. Often current is funneling food to the fish on and below the surface.

Man-made structures. No discussion of wood would be complete without discussing man-made stream improvements built by state agencies and conservation groups. Some of these are dynamite, some are duds. I’ve caught good fish from structures only to return to find the fish quit using them because the water level dropped. On some of the small streams I fish the nature of structures has changed. Instead of building hotels for the fish they’ve switched to placing trees and brush in the current to deepen the channel or change the current direction. Narrow and deep will hold more fish than wide and shallow. Fish will still associate with the structure, so always fish the features of the structure. They vary enough that you’ll have to decipher that. Some days a hopper placed right next to a structure in the current is just the ticket. 

Other man-made structures such as docks placed in a stream can likewise be dynamite or duds depending where it is placed in relation to the current, how deep the water is and so on. Landowners tend to place a dock where it is convenient for them to launch watercraft, or provide a good view for quiet meditation. Or drinking. A dock placed in shallow slack water won’t hold much; a dock in the current with good depth can work as a good fish holding structure, either to fish a streamer to, or float a dry fly down the outside edge.

Beaver structure. Beaver dams probably merit a whole chapter on their own. Trout tend to stack up on both sides of a dam. Fish the downstream side as you would any plunge pool/riffle area. Look for the deepest channel coming out of the dam to hold the biggest fish, but don’t ignore smaller chutes. Fish any dark moving water below the dam no matter how small the pocket. The upstream “pool” side of the dam will vary depending on water depth, age of the structure and whether there is structure and food above it. If there’s good current at the dam look for fish right on the dam in front of the out flow. If the water is slow and deep look for them upstream where there’s still some depth but the current first becomes perceptible again. This deeper water with current will remain good until it shallows out or you hit the next structure in the river. 

Beaver houses and muskrat lodges. On the streams I fish, beaver houses are more common than muskrat lodges, and also better places to fish. I list these separate because they’re not always associated with dams. If you find a beaver lodge randomly on a river bank by all means fish it.  Beavers will rout out the river bottom to create an underwater entrance to the home. Between the deeper water made by the beavers and the structure provided by the beaver house, these are popular spots for fish to hang out. For some reason baitfish are always gathered at a beaver lodge, adding to the appeal. Stand back and observe, look for some action, and if you can, drift a fly down the bubble line drifting past or into the structure. 

Beavers also make large caches of limbs to eat in winter or any time they don’t want to go to shore. It can be easy to confuse these with a beaver lodge. It will look similar but smaller, with most of the long branches piled up parallel to each other. These food caches also attract baitfish and trout.  Fish the outside edge of it.

Bushes and overhanging brush. Tag alders dominate brook trout streams in Michigan. They often form a solid wall on the banks, and sometimes a low, claustrophobic canopy overhead. They provide vital shading for the water, in-stream structure for the fish, and protection from aerial predators. This includes you if you think of flies as an aerial attack. During midday you can often hear fish feeding constantly, but the only rises you’ll see are deep in the tag alders. They often will move in and out of the tag alders or brush to avoid direct sun. Some streams have virtually no chance of ever being fished out due to having many miles of unfishable stretches of tag alders. The upper East Branch Fox River in Michigan’s Upper Peninsula is like this- miles of good water full of big trout, and so choked with tag alders it is not wadable or fishable.

Early, late, on overcast days, and during hatches like tricos the fish will leave the tag alders and feed midstream. Sometimes you’ll want to fish right along the edge of the alders. As vexing as tag alders can be, they are probably the key to life in northern brook trout streams. As easy as it is to hate them, tag alders may be the main or only reason that these small streams hold fish.

In Appalachia you can swap out tag alders for rhododendron and mountain laurel, both for their fish holding and sheltering capabilities, and also their angler confounding powers. On eastern mountain streams there tends to be a tall overstory of hardwoods, with a shorter understory of rhododendron and mountain laurel. Rhododendrons especially tend to grow out over the water more than mountain laurels. They serve the same functions as tag alders- shade, cover, structure, and protection. They present the same challenges to anglers. You’ll try and fail to avoid them while casting; look for fish to hold around them for the cover they provide. 

Grassy banks. Grassy banks are one of my favorite sights on a small stream. In the tag alder swamps of the north there is a tall variety of wetland grass that carves out chunks of riverbank for itself. It can be a small patch, or two hundred feet of riverbank. This grass tends to be undercut and thus provide cover for fish, food in the form of terrestrial insects, and possibly some open casting for the angler. Whenever I see a grassy bank I fish it hard, especially if it is undercut. Fish will be sitting right along that edge waiting for insects to fall in. They are great places to fish at night with mice too. Grassy banks are one of the most productive places to fish on any stream, so pay close attention any time you come across one.

Dams and waterfalls. I’m lumping these two together as they can provide the same opportunities and handicaps. One is natural, the other is not. They both provide fishing opportunities. This is a discussion of small streams, so we’re not talking about fishing to giants below Navajo dam. Waterfalls punctuate small mountain streams on a regular to continuous basis. A lot of small streams in other areas frequently have old man-made dams, either still working or broken or torn down. The downstream side of these will often cause fish to stack up, and you can either cast to rising fish on the tail-out or strip a streamer through the deeper water. Fish in mountains streams stack up in the plunge pool below a waterfall.  They will be hanging out at the edge of the boiling whitewater, and then in the tail-out below that. Sometimes I try to get my nymphs into the falling water, letting my indicator land below on the flat water so that the flies are driven down by falling water, but the indicator remains floating. Waterfalls that attract tourists can be surprisingly good fishing holes if you go when no one is there- early, late, or in the off season.

Jason writes the fine blog Fontinalis Rising

Jason Tucker

Gink & Gasoline
Sign Up For Our Weekly Newsletter!

Follow Gink & Gasoline on Facebook:

One thought on “Small Stream Structure- Woody Debris and Other External Features

  1. I will attempt to describe the alder lined section of water that I discovered years ago, that was full of 14-16 inch Brook trout. I began by dropping out of the forest into a fairly large river inhabited by browns and Rainbows. I waded across the deeper run under the trees until it shallowed up in the center, turned, and began fishing the run, getting my casts right under the overhanging branches. While fishing, I noticed splashes behind me in the shallow water, so I cast over toward the far shore and pulled in a small brookie. I began working the entire area, and got several small brookies in the shallows. I worked my way down, and noticed what appeared to be an offshoot entering the alders below me. As I neared the offshoot, the fish got larger. Right where the first alders hung over the water, I picked up a fat12-13 incher. Sweet! The water slowed and deepened as I entered the offshoot, and I had to slide tightly along the alders to keep the water from entering my waders. The center was easily 5 feet deep. I got another brookie out from under the alders across from me,14 inches. I worked my way down the offshoot, and came to a small island, about 10 feet long and 3 feet wide. Below the island I noticed a small brook flowing out of the jungle of alders and entering the offshoot on the far side of me. It created a hole where it entered, and I caught 5-6 more fat brookies from the hole, all 13-15 inches long. This was as far down the offshoot as I could go, as it got too deep to wade. I would have loved to explore further, but without a kayak it was not possible. I got hung up in the alders several times, but when I was able to get a drift, I had a blast fighting fat huge Brook trout. I went there several times after that, and got a ton of brookies, until one day I returned, noticed evidence of a canoe having been beached on the small island. I never got a single fish out of that offshoot since then. I’ve always felt that someone discovered the great fishing spot, caught and kept all the fish, and cleaned the spot out. What a bummer. So ended my only experience with fishing the alders. It’s not easy, but very rewarding.

Leave a Reply

Your email address will not be published.

Captcha loading...