Where to Fly Fish for Trout in Rivers: Explore the Riffles
What are Riffles? And Why Should You Try Fly Fishing There?
Standing along a river bank, you can recognize riffles by a few characteristics: Riffles are a shallow section of river that run anywhere from a few feet deep to just a couple inches. The river bottom is comprised mainly of pebbles, stones, and the occasional boulder. As it tumbles past you, the water will look swift and choppy.
Maybe you have tried casting your dry fly into that choppy water only to become frustrated with how quickly it gets pulled under the water by the current. You might even think that the water looks far too shallow to hold any trout, and if there are any trout they would be no longer than a couple inches.
Well as the summer months heat up, trout (and sizeable trout) move into riffled water for a number of reasons. If you pass by this water you just might be excluding some of the best water to fish during those hot summer days and even into early fall.
When and Why do Trout Hold in Riffles?
When water temperatures increase (think June through mid-September), riffles play a more important role for trout. As the water temperature heats up, the amount of dissolved oxygen in the water decreases which forces trout to seek out areas that have higher amounts of dissolved oxygen. Riffled sections of river churn up the water and this increases the amount of dissolved oxygen so trout will gravitate to these areas.
A trout's metabolism also ramps up with higher water temperatures making them feed more. These riffled sections of river are great habitats for aquatic insects, and as the current tumbles through those rocks, the insects become dislodged. This provides a nice conveyer belt of food for trout that are holding in the riffles. So trout are getting a nice meal and some decent dissolved oxygen to breath.
Lastly, riffled water provides protection from overhead predators like ospreys and eagles because the broken water makes it difficult for those birds of prey to peer through and nab trout. That riffled water also makes it frustrating for otters, minks, herons, and mergansers to travel through and hunt for trout. So, riffles give trout a place to feed, it has higher dissolved oxygen levels, and some protection from predators. Hopefully, riffles are beginning to sound more like an appealing place to fly fish, but let's continue.
Beyond the hot summer months, you can also explore the riffles during early fall when daytime temperatures are still steadily warm. Until the weather becomes routinely cold, trout will move in and out of the riffles to continue feeding. So from early summer to early fall, you can focus on fly fishing riffled sections.
Large trout will also move into riffles, but I have found this to be more the case when it is during low-light hours (dawn, dusk, and night) or even overcast and rainy days. Those larger trout move into riffles because there are plenty of aquatic insects in the riffles, smaller fish (like minnows, small trout, and sculpins) feed on those insects, and the larger trout will hunt those other fish (or feed on the insects themselves). This lends riffled water as an area to streamer fish as well (more on that below).
Key Things to Look for with Riffled Water
Now, before you go charging out and making cast after cast into the riffles, there are a few things that can help increase your chances of connecting to trout. First, you should look for a current that is of moderate speed. Riffled water can be really fast, but you will want to focus your efforts on water that is just bit quicker than walking pace speed. If the current looks like you would have to sprint in order to keep up with it then it is probably too fast. You should be able to stand and wade in the riffles.
Look for Small Depressions
Second, you will want to focus on riffled sections that are anywhere from a foot to three feet deep, but more importantly you should check for areas where there are variations in depth. These depth changes are formed by small depressions in the river bottom. Small depressions could be a few inches to a couple feet deeper than the rest of the riffles, and the length could be a few yards to just a few feet. These depressions are ideal spots for trout to hunker down in to stay below the swifter overhead current. They can hold some of the larger trout, so make sure you scan the riffles for those features.
Small depressions can be a bit tricky to locate at first, but a good sign to look for are any color changes in the water since deeper water will be darker colored or more blue. Small depressions can be near the banks, in the middle of the river, or anywhere in-between so take your time scanning for them. If these depressions are near the bank that has some overhead cover (like tree limbs or a cutbank) then that adds protection for trout and increases the likelihood of trout being there.
Boulders and Logs
Next, check for boulders or logs. Trout can sit downstream of these objects, but they usually will not hold right behind the boulder or log. Instead they will be a few feet downstream where the current is not so turbulent. Trout will also station themselves right in front of boulders and logs since there is a cushion of water that makes it easy for them to hold their position and feed from. Drifting a dry fly or holding a nymph right in front of a boulder can produce some surprisingly explosive takes. These boulders/logs can also create seams or bubble lines in the water that channel food which make it an ideal spot to float a dry-dropper.
Lastly, look up or down river for transitional zones. These transitional zones are where riffles meet slower or deeper water like pools, runs, or glides. Trout can hang out in a pool, swim upstream into the riffle to feed, then quickly turn around and bolt back to the deep water for protection if a predator attacks. This is definitely the case for larger trout that want nearby security. Trout will also hold along the drop-off between the riffles and deeper water. As the riffle heads into deeper water, trout will sit at the tailout of the riffle or right where the deeper water is. Work those transitional zones methodically.
How to Fly Fish in Riffles
Using Dry Flies in Riffles
Dry flies are a great way to fly fish the riffles, but the difficulty with dry fly fishing the riffles is keeping the fly floating once it lands on the water. The riffles are swift and can have numerous conflicting currents as they pass by boulders and logs, or flow over small depressions. This presents challenges to keeping the dry fly drifting along and not getting submerged. A key reason why a dry fly gets sucked under the current (or excessively dragged all over the place) is due to poor fly line management. Luckily, there are some ways we can minimize this from happening.
Line management is paramount when in riffled water and the first tip is decreasing how far you actually need to cast. In riffled water, the best way to get a good drift is to get yourself close to where you want the fly to land. You don't have to be super slow or quiet while getting into casting range, but wade thoughtfully. The trout cannot see as well in riffled water so use it to your advantage. You may also be able to utilize boulders or other objects to hide behind in order to stay hidden and close the distance.
Once you make a short cast, strip in any excess line, then hold the rod high (called high sticking) in order to keep as much of the fly line and leader off of the water. Keep that rod high and parallel to the ground during the drift, and continue to slowly strip in any slack line. This will help to keep the fly line from aggressively pulling on the dry fly while it floats along.
If I have to make longer casts in the riffles, then I typically find myself casting quartering upstream or parallel to the current. When casting in those directions, I will either make an aerial mend or will immediately mend the line upstream once it lands (and then make continuous small mends thereafter). If you don't mend the line immediately then it will pull the fly around and maybe even under the current thus limiting the chances of a trout taking it.
When it comes to the leader, you will want to use a shorter leader (around 7 feet) because this will aid in being able to high stick. When fly fishing riffles for most the day, I prefer a 7 foot leader that tapers down to 3 or 4x tippet. I like 3-4x tippet because I usually float larger "attractor" dry flies in riffled water (think Stimulators, Amy's Ants, Humpy's, Hippie Stompers, etc.). These large flies will also stay buoyant longer which helps to keep you in the action (and be sure you apply plenty of floatant to the fly before sending out that first cast), they are also good to use for dry-dropper rigs.
Using Dry-Dropper Rigs in Riffles
Taking our dry fly set-up from above, you can easily add a dropper and fish nymphs subsurface. I like to tie 12-18 inches of 4-5x tippet to the eye or bend of the dry fly hook. Tying the tippet this way allows me to easily clip the nymph off if the trout are mainly hitting the dry fly. The shorter length of tippet also helps to keep both the dry fly and nymph in the same seam/current of water rather than being pulled in two different directions, and the shorter length minimizes the number of hangups I have in the shallow water.
For nymphs, I like lighter weighted nymphs that are flashy and colorful, something to quickly catch the eye of a trout. You can even try using emerger style patterns that will float just below the surface. Always be ready to set the hook quickly, especially if that dry fly plunges under.
Wet Fly and Streamer Fishing in Riffles
Wet fly and streamer fishing are two other effective techniques to use in riffled water. A regular 9 foot leader (tapered down to 3-4x for small streamers or 4-5x for wet flies) works just fine since you will not need to be concerned with drag.
When I use wet flies, I will run 1-2 wet flies (either weighted or unweighted) and tie them onto the leader via a triple surgeon's knot. I like the triple surgeon's knot for wet flies because it allows each fly to move more independently from the other.
For wet fly fishing, most of your casts can be made parallel to the river's current or quartering downstream. Allow the wet flies to swing through the current, follow them downstream with the rod tip, and then hold them downstream of where you are standing. You can then slowly retrieve them back to you by stripping in a little bit of line at a time. Do this in front of any drop-offs/small depressions, boulders, logs, or cutbanks.
If I am streamer fishing then I prefer to use just a single small streamer (sizes 8-12) that is lightly weighted. It might seem strange to streamer fish in such low and choppy water, but since there is a higher abundance of insects in riffles, smaller fish (like sculpins and minnows) will move into these areas, followed by larger trout. Some of the best times to fish small streamers is during low light times or cloudy/rainy days.
If streamer fishing, casts can be made parallel or quartering downstream just like a wet fly, and even upstream. But after you make a cast, make sure to strip in the slack in order to maintain connection to the fly. A belly might form in the fly line due to the current pulling it downstream, this is fine if the streamer is still upriver of the fly line. What we don't want is for the streamer to overtake the fly line since that will create excessive slack and reduce any chance of feeling a bite. Using a floating fly line and weighted streamers (lightly to moderately weighted) should minimize this from happening and help to keep the streamer from zipping past the fly line.
Tightline Nymphing (Euro Nymphing) the Riffles
Tightline (euro) nymphing is a very deadly way of fly fishing riffles, but the subject could take up an entire article all on its own. So if you are already familiar with tightline nymphing, then try employing this technique in the riffles. I see plenty of tightline nymphers wading past shallow riffled water because it looks far too shallow and they are concerned with hanging their flies up on every cast. To prevent this, there are a couple quick tips:
Shorten up the tippet length from the sighter to the first fly.
Use lighter nymphs, dry flies, and/or emergers.
Keep the sighter high off the water, and practice watching for any movement in the tippet. Maintain a very high rod by keeping your arm up and out, and manage that slack line with your left hand.
You can also try greasing the sighter and tippet (with something like Loon Payette Paste) all the way to the first fly and then cast the line out. Keep your eyes on the sighter/tippet for any twitching or staling motion. This trick is best used for dries, emergers, and very lightly weighted nymphs when fishing the riffles (heavy nymphs will immediately plummet and snag to the river bottom).
Final Thoughts on Fly Fishing Riffles
Hopefully this article has given you the impetus to go out and fly fish the riffles if you have never tried it before. From early summer to early fall, the riffles can really be a great spot to connect to trout on the fly.
Before we end this article though, there are just a couple last things to keep in mind: Always be ready to set the hook. Trout that are stationed in riffles are more aggressive and opportunistic since they have very brief moments to grab a meal before it zips past them. Dry flies, streamers, nymphs, emergers, whatever, as soon as it hits the way you could have a trout immediately take it. Cast your fly line and manage that line so you have connection to the flies once they land on/in the water.
Finally, continue to explore the riffle and don't get hung up making twenty or more casts to the same spot. Trout won't school up in the riffles like they do in pools so it is best to venture out amongst the entire riffled section. If you do hook into a trout, then after landing it, really take a moment to examine where the trout was holding. Maybe even wade over to that spot and look at it. Was it deeper than the rest of the riffled area? Was it upriver or downriver of a boulder? Was the current near the river bottom significantly slower than the current near the surface? If you take the time to do this then you will rapidly progress your skill set at fly fishing the riffles.
Have fun out there!