When discussing fly fishing in Montana, May can be a double edged sword. On the positive side, the angler is presented with abundant hatches, ice free rivers, and hungry trout that are eager to feed and put on body mass. On the other hand, mountain snowpack is beginning to melt resulting in increasing flows and diminishing visibility on some of the area rivers resulting in rapidly changing conditions which can vary significantly from one fishery to the next. Because of these dynamic variables, anglers need to pay close attention to temperatures, weather patterns and the subsequent changes in water flows.
In general, the first half of May often provides the greatest diversity of fishing opportunities. On an average year, runoff hasn't taken over on the freestones yet and tailwaters are still seeing prolific hatches. As May grinds on, high water and poor visibility become more significant factors, especially on freestones, but quality fishing options still abound. We will discuss five of our favorite May fisheries and the various hatches of spring baetis, march browns, and Mother's Day caddis below, as well as some tips for getting fish in the net when conditions aren't as "hatchy".
Keeping all of these factors and nuances in mind, it is always challenging and inherently subjective to label anything "the best". We have selected five of our favorite fisheries on which to focus, but this is not an exhaustive list by any means.
1. The Yellowstone River
The Yellowstone can produce prolific hatches of spring baetis (blue winged olives), March browns, and caddis. Baetis and March browns will be found early in the month when the wet and cloudy weather moves in. The legendary Mother's Day caddis hatch can produce blankets of insects on the river in the first half of May. Typically the caddis hatch on warmer days. There is a bit of a "Goldilocks" requirement to enjoy good fishing over this hatch on the Yellowstone since you need warm enough weather for the hatch to commence, but cool enough to prevent runoff from beginning. Dry fly fishing is never consistent on the Yellowstone in the first half of May, but when the stars align it can provide some of the best match the hatch fishing of the year. Nymphing and streamer fishing can also be very productive on the Yellowstone in May.
Blue Winged Olives are the first major hatch of the year on the Yellowstone, generally appearing in late March or early April and persisting into early May. Look for BWO to start coming off the water around lunch time through the warmest part of the day. Hatches tend to be more prolific on cloudy days so the more cloud cover the better. Basic mayfly attractors like a Parachute Adams or Purple Haze will likely get the job done, but it's never a bad idea to have a specific baetis pattern in sizes #16 and #18. As with most hatches, to maximize catch rates you will want imitations for each cycle of the hatch from nymphs to duns.
March browns are a large mayfly common to our cobbled western rivers and is the first "big bug" hatch of the year. You are more likely to see march browns hatch in scattered pockets throughout the river as opposed to a blanket hatch. They emerge rapidly shedding their nymphal shucks on the bottom and ascending to the surface. Swung fly presentations can be deadly in waters that contain these neat mayflies. Generally, duns begin appearing in the early afternoon followed by the spinner fall in the early evening. Though a parachute and a cripple dropper will sometimes entice strikes, trout can be picky with this short-lived hatch so I try to load up on specific march brown patterns in the spring.
It seems most years that right as the excellent numbers of caddis appear the river huffs and puffs and blows right out. However, the weeks before the appearance of the caddis can be some of the best dates of the year. Look for cold fronts to arrive that will temper the snowmelt and allow the river to drop and clear. When decent visibility couples with water temperatures sneaking above 50 degrees, anglers will have the perfect recipe of quality dry fly fishing for up to a week. Many anglers choose to focus on the Paradise Valley stretch of the Yellowstone, with the goal of fishing upstream of tributaries such as the Shields which can dump mud into the river and subsequently reduce visibility. When targeting the caddis hatch, a size #14 elk hair caddis in tan, light brown, or olive is a go to pattern. Because trout will often key in on a specific stage of the hatch, it is savvy to fish a caddis emerger or pupae as a dropper behind the dun, enabling the angler to target multiple stages of the hatch at once to potentially increase catch rates. A majority of the feeding activity will take place along the banks in softer water, allowing the float fishing angler to cast to rising fish while drifting. When a pod of feeding fish is located, consider anchoring below and working the productive water on foot.
Even when the river is off color and fish aren't rising to caddis or BWOs, subsurface fishing can produce some outstanding trout. When nymping, anglers don't need to get too technical with their rigs; a stonefly nymph such as a Pat's Rubberlegs in black or brown with a caddis attractor dropper like a Prince or Lightning Bug will get the job done. Depth is important, especially to avoid a whitefish rodeo which can occur when fishing too high in the water column. Employing the right amount of split shot or other sinking agent and adjusting the location of your indicator is probably more important than the precise pattern you are fishing.
Though many anglers associate stripping articulated streamers with fall fishing, some of the best trophy tout of the year are caught on the Yellowstone in the spring on streamers. Usually, streamer fishing is a low numbers game, but can produce aggressive strikes on some truly large fish. weather can be a key factor here, with large browns notoriously wary on bright and sunny days. Take advantage of cloudy or rainy spring days to swing for the fences with your favorite sculpin or baitfish patter.
2. The Paradise Valley Spring Creeks
The Paradise valley spring creeks offer consistent fishing and clear waters in the month of May. Predictably clear water and strong hatches of baetis and caddis make DePuy, Armstrong and Nelson spring creeks great May options. Baetis (aka blue winged olive) hatches can still be strong in early May, especially on overcast days. As we move into late May and the days get warmer and longer, keep an eye out for the Mother's Day Caddis. The caddis hatch heavily on the neighboring Yellowstone River and on windy days will into the creeks. Although the spring creeks always produce a technical fishing environment. The fish, while wary, can be taken with a proper pattern and presentation. When the fish aren’t rising everything else remains on the table; streamers, mice, and nymphs all play. Patience, persistence and observing the insect and fish behavior while you fish is key on the spring creeks in May.
The smaller ranch lakes in Big Sky country can provide quality fishing for quality trout. As the ice has recently receded the fish have gained solar warmth and are on the prowl for food. As with the spring creeks, stillwaters offer the angler consistent and predictable conditions through May. This is one of our favorite times of year to target some of our private ranch lakes in the area. While small insect imitations can work, this is the prime season to take fish on stripping leeches. Explosive grabs and trout measured in pounds not inches characterize the still water scene.
4. The Madison River
We consider the Madison to be the centerpiece of May fishing. The Madison provides 31 days of quality trout fishing in May. While symptoms of runoff do present on stretches of the Madison in May there is always fishable water. The waters from Hebgen Lake to Lyons Bridge provide the best opportunities for numbers and the greatest diversity for angling opportunities. Additionally, this stretch is closed to fishing from the boat forcing an intimate angling situation. Some years the river provides solid fishing from Hebgen to Ennis. During especially wet springs the tributaries will contribute significant color, usually this occurs sporadically. The river below Ennis Lake produces consistent fishing to Cherry Creek without fail. Sporadic pushes of dirty water will temporarily shut down the water that exists below.
5. The Missouri River
The Missouri River tailwater near Craig offers consistent flows during the month of May. Early in the month some of the rainbows in the system are still in the spawning tributaries such as the Dearborn and Prickly pear but there are still plenty of rainbows in the main river after the spawn as well as some large browns. The Prickly Pear can add a bit of color as runoff begins later in the month but generally not enough to interfere with fishing. The Dearborn is a larger system and in mid late May it can flow high and dirty. Below the Dearborn the Missouri loses clarity. Keep in mind that even if the river looks dirty, it often still has good enough visibility for good nymph and streamer fishing downstream of the Dearborn. Early in May baetis hatches are still lingering, especially on cloudy days. Caddis begin appearing later in the month. Dry fly fishing tends to be centered around hatches, especially the baetis early in the month. Nymphing can be especially productive in the month of May and the weedbeds that can complicate subsurface fishing later in the summer are still sparse in the spring.