We are in the midst of the pre-runoff part of the season here in early May. Most of the freestone rivers have a week or two of good fishing left before the brunt of runoff hits but fishing conditions can be day by day. Warmer than average weather will cause some rivers of the freestone rivers like the Yellowstone to rise quickly and become off color while cooler weather with freezing temps at night result in falling and clearing waters. We have some of our heaviest hatches of the year on many of our waters with baetis, March browns and Mother’s Day Caddis all in healthy supply – often over the course of the same day. Tailwaters, spring creeks, and lakes are not affected much by runoff and fishing will remain good.
On the freestone rivers, the most important thing to pay attention to is water flows and clarity. This is a very dynamic time of year on our rivers and what happened yesterday is not a great indication of what is going to happen tomorrow. Trout feed best on stable and falling water levels and rising water usually puts them off the bite. The water level and clarity is very important, but whether the water is rising or falling to reach that level is equally important, if not more so. In general, rapidly rising waters will almost always spoil good dry fly fishing, but slowly rising waters may produce some color in the water but fish will still aggressively eat subsurface. On tailwaters, such as the Missouri and Lower Madison, the flows will be bumped up incrementally during runoff. The fishing is generally off for a day or so as fish adjust to the new level, but the fishing quickly returns to normal with the stable water levels. The other consideration on tailwaters is that freestone tributaries will bring in mud. Example of this are Cherry Creek on the Lower Madison and the Dearborn River on the Missouri. Be aware of this and choose to fish upstream if these tributaries are bringing in mud. Spring Creeks are generally completely unaffected by runoff.
Nymphing is going to be the best bet on all waters in the morning and during non-hatch periods. If there is too much color in the water fish may also feed subsurface even during heavy hatches. Your best chance at dry fly fishing will be found on the Yellowstone, Lower Madison, Upper Madison and Missouri, which all have daily hatches of Caddis. Cloudy days could bring mayfly hatches to any water in the region, but they are somewhat sporadic this time of year.
On freestone rivers, the best bets will be “big and ugly” type stonefly nymphs with caddis droppers. On cloudy days with heavy mayfly hatches try a baetis nymph or large hares ear to imitate the big March browns. Aquatic insect larva and nymphs are getting very active as they prepare to hatch. “Junk” flies like eggs and San Juan Worms will produce as well. On spring creeks and tailwaters, try things like scuds, sowbugs, Czech nymphs, etc. These nymphs represent food sources that are available to trout 365 days a year.
The Mother’s Day Caddis, one of the best hatches of the year, is upon us. The Yellowstone River around Livingston and in Paradise Valley and the Lower Madison River are the best locations to chase this hatch. The Upper Madison also receives a good hatch in the lower reaches. The bugs are typically active from mid-morning on, with the most intense activity in the evenings. The dry fly bite is sometimes good all day but tends to really pick up as the sun starts to come off the water. The fish will eat adult imitations well, but oftentimes an emerger pattern trailed off of the back of your dry will outfish the dry by a wide margin.
Also be on the lookout for March Browns, especially on the Yellowstone River around Livingston, the Lower Madison and the Upper Madison near Ennis. The March Brown hatch is hit or miss, but the fish really key in on these large mayflies when they are available and on a cloudy day they can bring large fish to the surface. A Parachute Adams or large Grey Wulff will do the trick sometimes but it’s nice to have a couple more realistic imitations tucked in your box just in case.
Blue Winged Olives are starting to thin just a bit but will still be important on cloudy days, especially on the spring creeks. As with the Caddis hatch, fish will oftentimes key in on BWO emergers, so make sure you have the fly patterns to cover all stages of the hatch.