When & How to fish Mop Flies

For reasons I could never fully understand, mop flies are seen as “controversial” and “trash flies” by many anglers. If you are an individual who falls into this category and refuses to fish the mop, great. Don’t use them and stop reading now. For the more open minded, I’d like to share some of my experiences with mops below, including when mops work very well (and when they don’t) and how I typically fish them. These techniques are mainly targeted towards fishing with a mono-leader (Euro-nymphing) and I feel in the majority of situations will work far better with this approach, but they could absolutely still be used with a standard fly line or indicator set up.

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When to fish a Mop

High Water

The first, and probably most well-recognized, situation in which mops can excel is in high or dirty water. In addition to fishing streamers on a mono rig, mops are one of my go-to strategies in these conditions. When visibility is limited, mops present a large profile and bright coloration (chartreuse is my favorite for dirty water) that fish can key in on. I also believe there is a second reason that mops work so well under these circumstances. Due to their mass and the way they soak up water, mops tend to drift slowly once they have reached the strike zone, near the bottom. These slow drifts give fish more time to see your fly, which can be the difference between catching a fish and not in dirty water.  

Something that I constantly have to remind myself when fishing in high-water is to use less weight than usual. The vast majority of the fish I catch when the water is high and dirty are tucked in right along the banks, often in water less than a foot deep. Since this water is shallow and usually not flowing very fast, a lightly weighted fly is all that’s needed to get deep enough. The fly should be drifting, not dragging bottom.   

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Runoff season in the West is perfect mop conditions. In some of the worst visibility I’ve ever fished in, mops and streamers in shallow water along the bank provided some nice browns.

Low Water

Another situation where mops can be a deadly change-up is when the rivers are low and clear. In many of the Vermont rivers I fish, trout love to tuck up under rocks and logs as soon as water levels drop. One of the most successful methods I’ve found for pulling fish out of cover in conditions like this is to drift a mop as close as I possibly can to undercut rocks, banks, logs, etc. I find that mops are able to draw fish out of cover when a smaller nymph might not. I’ll most often fish a mop on its own in these scenarios, to get a better drift and to avoid having a dropper hang up on cover. I have a lot of confidence in a cream/tan mop in low water. I love the natural look, and the trout seem to also. 

In low, clear water when fished are tucked under cover, mops can have much more pulling power than a smaller nymph.

Spring Creeks

I can’t claim to be a spring creek expert, but in the ones that I have fished cream mops have been far and away the most effective pattern. I’ve been most successful dead drifting them, both sight-fishing and through likely holding water, but I’ve caught fish stripping mops and crawling them along the bottom. The slow sink rates of mops are great in flatter spring creeks where the current isn’t very strong. A nymph that sinks quickly, like a perdigon or other slim-bodied fly, can often times attain depth too quickly and ruin the presentation, even when lightly weighted. On the other hand, a mop will sink slower and provide a more natural drift. Because mops are so visible to the angler, sight fishing with mops is certainly an advantage, as it allows you to see if your drifts are actually going in front of fish.

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This was a day of mopping I’ll always remember. Between my two brothers and I, we caught around 100 nice cutthroats, almost all on cream mops in a heavily pressured spring creek.

Deep, Slow Water

Another circumstance where the slow sink rate of mops is an advantage. The weight of the mop also helps keep contact with the flies in this water type. When fishing the deep and slow stuff, don’t be afraid to even just let your mop sit for a long period of time. Sometimes I’ve caught fish after over a minute of the mop sitting in one place, twitching it every few seconds. My friend and fellow mop-enthusiast, Franky, also likes to fish mops like you would a jig streamer in water like this. Because the tail of the mop moves so much when jigged, he’ll get reactionary strikes from fish in slow water with this technique. It can also be very effective when sight fishing to uncooperative fish.

Windy Conditions

When fishing a mono leader, nothing is more frustrating than a windy day. Wind can ruin drifts and drastically reduce contact to flies. My go-to approach in windy conditions is to fish streamers or indicator nymph, but if these don’t seem like productive options than a mop can save the day and allow you to keep tight line nymphing. As I mentioned before, mops soak up a lot of water and like to stay put once they have reached the slower water near the bottom. Because of this weight, they help anchor your rig when wind is affecting your leader. I also like to fish a heavier mop in wind than I normally would and run a shorter section of tippet under my sighter. In order to keep contact, I will then lead my rig significantly more than I ordinarily would. All of these changes help ensure a decent degree of strike detection.

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Another victim of a cream mop sight-fished.

Pressured Fish

This is a scenario when a mop is certainly hit or miss. Some tailwaters or otherwise heavily pressured rivers I fish the mop catches hardly any fish, while on others it’s lights out. For instance, on one East Coast tailwater I’ve fished a handful of days a chartreuse mop absolutely cleans up. No other pattern or presentation I’ve used even comes close. Because the mop can be such an all or nothing fly under these circumstances, it’s worth giving it a few minutes to see if it will work. If nothing happens, don’t spend too much time with it and move on to something different.  

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This 20.5” brookie from a pressured tailwater aggressively took a mop.  

Migratory Fish

Fish running up from lakes can act pretty weird, so at times something weird like a mop can do the trick. I’ve caught some kings from the Salmon River on mops and hooked a good number of Vermont steelhead and landlocked salmon. It can be hit or miss but worth a shot.  Don’t be afraid of a swung mop either!

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My friend, Franky, with a king that he watched move several feet to eat a mop.
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A LLS that I recently got on a cream mop under very windy conditions.

When not to fish Mops

I’m a strong believer that anything can work at any time, but there are some situations in which mops don’t offer a strong presentation. I find that in water when a fast sink rate is necessary to get down to the strike zone a bulky mop, even if heavily weighted, does not fish well. For instance, in rapid pocket water, mops don’t really have the ability to get down to where the fish are before the pocket ends.  When this is the case, I find  more traditional nymphs to be far superior.  

Other times fish really don’t want to eat mops. It will be pretty easy to tell if this is what’s going on because you won’t be catching anything, even if you’re drifts seem great. The mop is a good fly, but it certainly works more sporadically than typical attractor nymphs.

Leave a comment below if you have something mop-related to add. I’d love to know if you’ve found similar results to what I’ve experienced, or something completely different.

A Note from the Editor: 2 Additional Mop Scenarios

Do not underestimate mops, I’ve caught some of my personal best fish on them, and have seen them work when nothing else could fool a fish. I’ve even had one of my mop flies come unfurled from the abuse it was receiving from fish, in this state it honestly looked like a small mop-variation of Mangum’s Dragon Tail Tarpon Fly. The mop material was unraveled and tapered off the back of the hook about 3 inches. I decided to keep fishing it and continued to land fish with this mangled mess. Needless to say, I’m a mop enthusiast and would like to offer a couple more ideas for when and how to fish these strangely effective flies;

Winter Tailwaters

Fishing a tailwater in the winter with a mop can be a great way to euro-nymph while still fishing appropriately sized bugs. If you’ve ever tried forcing your typical euro nymphs on picky tailwater trout in the winter, you’ve likely struggled to connect with these pressured fish. With most commercially available jig hooks a size 16 is about as small as you can go, which isn’t close enough to the naturals to be all that appealing to a wary tailwater fish in the winter. The majority of nymphs fish are keying in on during the cold months are quite a bit smaller than that. In fact, when in doubt, it is advised to err on the side of being undersized with most midge patterns. A good solution to this situation is using a mop as an anchor. By fishing a 2 or 3 fly rig on a euro-leader, you can use a mop fly to bring the whole rig down to depth while still presenting your staple wintertime midge patterns. Not to mention, in rivers with a strong population of craneflies (think Colorado’s famous South Platte) a cream colored mop is actually a great imitation of these protein-packed grub-like bugs. Next time you’re out winter fishing, try throwing a heavy mop with 1 or 2 size 18-24 nymphs tied onto tags. You can fish the mop either as a dropper fly or the point fly, I have tried multiple configurations and have had success with all of them.


On stillwaters, a mop can be used to imitate a cased-caddis or sedge. tan, cream, and chartreuse have all worked for me. In my experience, these patterns are best fished when crawled under an indicator on any lake, pond, or reservoir with trout. Heavier mops will be effective at probing the depths but a lightly weighted mop will be more neutrally buoyant and can seal the deal on a trout cruising the middle of the water column intercepting emerging insects on their way to the surface.

About the Author

Calvin McClellan@jah_eel_vt

I’m an Environmental Science major at the University of Vermont who spends way more time fishing and tying flies than I probably should.  Although I do enjoy a good dry fly or streamer take, I most often can be found using European-nymphing techniques to target the wily wild browns, ‘bows, brookies and salmon of the Green Mountains and neighboring states.  While I’ll always have a love for the challenging (and sometimes frustrating) streams of Vermont, I often migrate West during the summer to fish remote rivers and alpine lakes.

2 thoughts on “When & How to fish Mop Flies

  1. I live 400 miles south of the San Juan River and the drive is agonizing. If you don’t fish on a regular bases trying to figure out the water and fish is more agonizing. I was introduced to the “crane fly larva fly” and it saved my day. I caught fish on other fi lies but the mop was outstanding. Call it a trash fly but it can turn a bad day into a good day. I did notice that it attracted smaller fish but I only fished it for a couple of hours (50 fish +). When I got back home I ti d up and 20. RainX mop tan

  2. My experience and opinions are almost identical to those described in your article. The information provided was helpful because of greater familiarity with western rivers and fly fishing with nymphs, streamers and dry flies. After moving to the New England area recently I’m in the middle of the learning curve for the nuances of eastern rivers and Northwoods lakes. A mop fly is a new pattern that I have fished with so far for only just one season.

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