May is perhaps the most dynamic times of year to fly fish in Montana, yet it flies under the radar for most visiting anglers. It is a month of significant change; river levels, weather patterns and insect hatches can change quickly from one day to the next. As water temperatures warm quickly the trout really start putting on their feed bags and the fishing can be downright explosive at times. Fishing pressure is relatively low during May, and coming off the long Montana winter, the fish haven’t seen many flies yet. May offers great hatches as well as some excellent nymph and streamer fishing. It is the favorite time of year for many local anglers and guides.
One of the most exciting things about fishing in May is the variety and intensity of the hatches. While the Stonefly hatches of early summer and hopper fishing later on garner most of the fame, a strong case can be made that the best dry fly fishing of the year takes place during the spring. Strong mayfly and caddis hatches take place on most waters throughout our region.
Blue Winged Olives
The BWO’s, or Baetis, are the first major hatch of the year. By May, BWO’s will hatch most consistently on cloudy days. The hatch usually comes off mid-morning lasting until early afternoon, although this timeline can be pushed back on the coldest days. I have noticed that the trout, especially the Rainbows, tend to pod up during this hatch. You will often go through a stretch of water where nothing is happening only to round a bend and encounter a pool or eddy with dozens of fish rising enthusiastically. While you want to carry some specific Beatis patterns, you can often get away with a mayfly attractor like a Parachute Adams or Purple Haze. The spring Beatis are usually a bit larger than those in the fall, so #16 and #18 flies are your best choices.
The March Brown is the first “big” bug to hatch each season, as these mayflies typically come in a #12 or #14. Despite the name, March Browns are important hatch during the month of May. You won’t often find a blanket hatch of the March Browns, but they will be found in scattered pockets on many rivers. The March Browns are particularly interesting because the fish will often get keyed in on them. I have been in situations where there were thousands of caddis flies floating down the river unmolested yet every single March Brown on the water was being devoured. Trout often take these large mayflies with abandon, creating large splashes with each rise. To match this hatch, I prefer a specific imitation rather than a general attractor. While a Parachute Adams or the like will probably do in a pinch, I like to stock up on some March Brown patterns from the local fly shop each spring. If there are March Browns on the water, I want one on the end of my line.
Mother’s Day Caddis
This is the main event, folks. The Mother’s Day Caddis is a legendary hatch, and my personal favorite of the entire year. There can be a literal blizzard of caddis in the air, appearing as huge oscillating waves over the water. While every year is different, the first week to ten days of May is usually the best timing for this hatch. It seems that when the water temperature creeps above 50 degrees is when things really start to happen. When the hatch is really cranking you can have dry fly fishing all day long, although afternoons and evenings tend to be the most consistent times. For flies, I like an olive or tan imitation in a #14. Sometimes I drop to a #16 if the water is exceptionally clear. Popular patterns include the Elk Hair Caddis and X-Caddis. I will often fish an emerger or pupae as a dropper behind my dry fly.May Fishing Destinations
Recent rule changes in Montana have really opened up the options for fishing in May, especially early in the month. The state has eliminated the general fishing season, meaning that most rivers and streams are now open year-round. Previously, these waters opened to fishing the 3rd Saturday in May, meaning we now have many additional options for pre-runoff fishing that didn’t exist before.
Fishing on the Upper Madison will greatly benefit from the new regulations. The entire river between Hebgen Lake and Ennis lake is now open year round. This opens up some fantastic fishing opportunities for both wade and float anglers. Wade anglers can now fish the famous “Slide” and “Channels” section year round. Both of these sections will fish very well. Float anglers will now have access to the stretch between Lyon’s Bridge and McAtee Bridge year round. This tends to be the most crowded part of the float section, so anglers will now have the opportunity to float this stretch in relative solitude during the spring.
The Upper runs through a series of lakes, so runoff is delayed here and the river typically fishes well through the entire month of May. While the Upper will offer up some pockets of dry fly fishing, nymphing is the mainstay here and can be extremely productive, both in terms of numbers and size of fish. Rubber Legged Stonefly’s in a variety of colors and sizes are popular lead flies. Effective droppers include various Prince’s and Caddis Pupae in #10-14, and smaller Baetis nymphs in #14-18. The Madison is a very swift, rocky river so anglers will want to focus on the slower water created by boulders, islands, and shelves in the river.
The Lower will continue to be one of the best and most popular options during May. Ennis Lake provides shelter from runoff and the Lower typically fishes very well throughout the month. The main attraction on the Lower during this time will be the Mother’s Day Caddis hatch during the beginning of May. The Lower, along with the Yellowstone, is the premier destination for the hatch. The advantage of the Lower is that water clarity due to runoff is not an issue, which cannot be said for the ‘Stone. Swarms of caddis will be seen along the willows each afternoon and evening, and the dry fly bite can be fantastic. Cloudy, rainy days can see hatches of Blue Winged Olives.
During mornings and non-hatch periods, the nymphing is typically excellent on the Lower. Popular patterns include San Juan Worms, Crayfish, Prince Nymphs, and Pheasant Tails. The Lower is a fairly shallow river, so even during the higher flows of May you can fish the entire river. The banks will hold fish, but mid river structure such as boulders, islands, and weed beds will produce as well. Both wading and floating are productive during May.
The Yellowstone can be a dynamite fishery during May, but it is dependent on water conditions. The ‘Stone is a freestone river, meaning there are no dams along its course. The Yellowstone typically enters spring runoff towards the middle of May, but every year is different. There is typically a period off good fishing early in the month, but it can be day by day. Warm weather will melt snow and muddy the river, while cool weather will clear the water. The river will typically yo-yo in an out of fishable shape throughout the spring before runoff hits for good.
Like the Lower Madison, the Yellowstone is well known for the Mother’s Day Caddis hatch. If the water is clear, it can seem like every fish in the river is rising. The Yellowstone also has the best March Brown hatch in our area. This hatch is much more scattered and hard to predict than the caddis, but if you happen to catch it right the fishing will be lights out. Cloudy, cold days will typically see some blue winged olives around lunchtime.
During non-hatch periods the ‘Stone will see pretty good nymph fishing with Rubber Legged Stonefly’s and various Caddis attractors like Prince’s or Lightning Bug’s. The ‘Stone is a great streamer river, and May is a great time to swing for the fences. While most anglers associate the Fall with targeting large trout on streamers, many local fisherman and guides prefer the Spring.
May is a great month on our local Spring Creeks. They offer great fishing with the added bonus of being crystal clear and fishable every day of the month. While the famous creeks of Paradise Valley (Armstrong’s, Depuy’s, Nelson’s) are the main draws, there are many lesser known creeks in our area. Due to the recent regulation changes, these creeks are now available to us the entire month of May. Many of these smaller spring creeks become too weedy to fish effectively later in the summer, so we are now able to fish them under prime conditions.
During May, the Spring Creeks will see good hatches of Blue Winged Olives and Midges on cloudy days. You can always find sporadic hatches and risers on these creeks, but the best dry fly fishing this time of year will be on cloudy days. Nymphing is always good on these creeks, especially early in the season when the trout have not been pressured too much. Smaller patterns such as Scuds, Sowbugs, and various midges are the staple here.
Most freestone rivers in Montana generally enter runoff during mid to late May on a typical year, so our new regulations will allow us a pre-runoff season that we didn’t have before. This will allow our guides to get creative and really open up the options available to our guests. Many more well-known rivers such as the Gallatin, Boulder, East Gallatin, and Ruby will continue to offer great May fishing as well. We also have some excellent lake fishing during May. The ice is just coming off many ponds and reservoirs and the fish are feeding voraciously. May is a great time to strip a leach pattern and go for some of the biggest fish of the season. Some of the lakes that we fish have an average size over 18” with some trout pushing 26”-28”. The bottom line is that May has always been a great time to visit and fish and has now only gotten better with the additional options available.