Pretty much not a bad place to fish right now in Montana! Water levels are slowly dropping on rivers and streams. The snow pack is not completely gone so the flows are still at higher levels and the water temps are still on the cool side. Trout love falling waters and the rising water temperatures are triggering a cascade of aquatic insect hatches. Peak activity this time of year coincides with the emergence of aquatic insects during the hatches. The peak hatch times depend on the fishery, on cold mountain streams, spring creeks, or some rivers that just cleared but still have a lot of snow melt water feeding them the hatches don’t begin until late morning and often run from 11am until 3pm. On warmer fisheries that have already been clear for a while, or ones at lower elevations, the emergence is early in the morning, sometimes as early as 8am and things are wrapped up by lunch time. Make sure you are on the water when the bugs are because that always coincides with the best fishing. If you arrive before the hatch try streamer fishing or deep nymphing. Make sure you have imitations of the insects that are hatching. Depending on where you are this could be pmds, yellow sallies, golden stones, salmon flies, caddis, etc. Also play close attention to the insects on the water at a given time, often PMD’s hatch before yellows sallies for example. On highly fertile fisheries with thick hatches like spring creeks and tailwaters the trout become very selective during the hatch and you must imitate the correct species as well as life cycle of the insect that the trout are keying in on. On less fertile freestone streams it is more of a potluck and the trout will feed more opportunistically. On spring creeks plan on match the hatch but if you are fishing waters with sporadic hatches try big attractor dry flies on top or large streamers down under to move fish farther than smaller patterns. Expect to fishing to slow down abruptly once the insects are gone but you can often continue to pick fish up later in the day. In the evenings there is often another flurry of activity just before dark.
We are experiencing a rare event of awesomeness in its totality at the moment where everything is awesome in the Montana fly fishing universe. This doesn’t happen every season and it doesn’t happen for long…but it is happening right now. You simply can’t find a bad place to fish right now. The Smith River is low but still floating for another week and fishing great. The Yellowstone River is a little high but runoff is over and it is of course fishing awesome. The Missouri is in its abundance of mayfly hatch nirvana as a parade of PMDs grade the water each day….and fishing is of course AWSOME. Damsel flies are popping on ranch lakes, the Firehole in the park is close to the end of its run BUT still awesome in the mornings. The Yellowstone inside the Park has just dropped to fishable levels and maybe only 85% awesome, but still not too shabby. Salmonflies are even popping on the Upper Madison. So there you have it - sheer and complete awesomeness.
Overview
Stonefly nymphs are going to be getting more and more active as water temperatures warm. Fishing the banks and "walking speed" water will be the primary focus for the next couple of weeks. Target bankside structure like rocks, logs, etc. On rivers like the Madison this is the time of year to focus on the banks. On the Gallatin and Yellowstone this is the time of the year be sure to use shorter leaders and stout tippets because you are not likely to be able to see the structure and if you snag up you want a stout enough leader so you don't lose too many flies.
If you want to fish crystal clear water and try some more technical fishing--either dry fly fishing or shallow water/tight line nymphing action, choose the Paradise Valley Spring Creeks or the Missouri River.
Hatches
Caddis, stoneflies, golden stones, yellow sallies, and PMDs.
Fly selection
You basically have to determine if you are going to match the hatch or bust the hatch this time of year. When you can see fish actively rising on the surface it is generally best to match the hatch. The same as true before a hatch, nymphing with the imitation of the nymph or emerger that the fish will see later is a good bet. When the hatch starts if fish are on the surface it is best to match the hatch or try a “cripple” or “emerger” pattern behind an adult imitation. If the hatch gets to a blanket stage then try a size or two larger than the natural. If fish are not taking flies off the surface then the nymphing game can be tougher during the peak of the hatch unless you are sight casting. There can be so many naturals underwater that your imitation has beat the odds that are often 100:1 with so many real bugs in the water. If you are nymphing during a strong hatch it is often better to switch to much larger patterns or streamers dead drifted or stripped rather than compete with naturals.
Interestingly when a hatch is sparse we flip flop are strategy. On the surface you can still catch fish with an exact imitation but you can often be even more successful with a large attractor fly that will move fish farther. The trout aren’t so keyed in on the natural that they won’t switch gears and eat something even bigger like a fat albert or chubby Chernobyl. When nymphing it is nice to continue to have an exact imitation but consider trailing it behind something larger like a big stonefly nymph, crayfish or sculpin.
Parachute Adams in sizes 12-18
Comparaduns in sizes 12-18
Royal PMX in sizes 10-12
Beadhead Little Green Machines in olive or natural in sizes 16 to 22
Pat's Rubberlegs in contrasting colors in sizes 6-12
Beadhead Pheasant Tails in flashback or natural in sizes 12-22
Firebead or hot bead SJ wormies in sizes 8-12
Beadhead Perdigons in natural, olive, peacock, black, in sizes 16 to 22
Sawyer Pheasant Tails in sizes 16 to 22
Home Invaders in darker/contrasting colors in size 2 - 10
Sculpzillas in black, olive, or brown in size 2- 10
Sparkle Minnows in a variety if colors in size 2 - 10
Elk Hair Caddis in sizes 10-18
Buzzballs in sizes 16-22
Your favorite go-to streamer pattern
Reading water
Flows are all over the place right now on different rivers. On fisheries that have already dropped significantly trout are already moving into deeper runs for protection but on the rivers with higher flows they are in the safe havens that have slower current speeds like along banks, behind rocks and on the inside corners of bends or slower tail-outs. On our freestones reading water right now it relatively simple--fish the banks and bankside structure and find slow water near the structure. On our tailwaters and spring creeks, the game is a little bit different. It is important to pay attention to a river's pockets, seams, riffles, runs, and pools. Because the main hatches right now are caddis and PMDs, fish are going to be scattered. Caddis are going to hatch from riffles or along the banks and PMDs are going to hatch at the start of runs or in shallow riffles. The place to look for trout during these two hatches are where two speeds of water mix. Focus on current speed and depth changes. The composition of the bottom is also important on tailwaters and spring creeks. This can give you a clue to the type of insects that might be hatching...especially in a spring creek or tailwater. PMDs most likely will hatch from streams with small cobble or tiny gravel.