Some of Montana's best hatches occur early in the season before the rivers become swollen with snowmelt. Savvy anglers have realized that targeting these hatches can provide some fantastic early season dry fly fishing. Many Montana fly fishing guides rate the spring as their favorite time to hit local rivers.
Dry fly activity begins in earnest in the late winter months of February and March when midges begin to hatch in enough abundance to interest trout. Most early season hatches occur in the middle of the day when water temperatures peak. Midge hatches, however, tend to occur in the late morning so it is important to make sure that you get to the water well before noon. Midge hatches can often be very thick with the insects hanging on to each other in clusters. For this reason, patterns that imitate a midge cluster such as a Griffith's gnat can be very productive. The larger cluster patterns also move fish farther than individual patterns. When the hatches are sparse, individual imitations such as a palomino midge can be very productive.
The first large insect to hatch following the diminutive midges is the skwala stonefly in late March and early April. The skwala is a smaller size 12 stonefly that is dark olive in coloration. The insects do not occur in great abundance and their smaller size and dark color make them difficult to spot, but they come off in enough quantity to entice trout to the surface. The allure of catching fish on dries after a long winter of dormancy is too much to resist for most local anglers. The skwala is not the kind of hatch that you will frequently cast to rising fish. It is far more effective to fish the water searching with your favorite skwala pattern.
As water temperatures begin to rise in April, insect activity increases. Several different species of the baetis mayfly begin to hatch in increasing abundance. Baetis are commonly referred to as blue winged olives and the gray and olive insects can be typically with a variety of size 18 patterns. Baetis notoriously hatch in much greater abundance on cloudy days; the worse the weather the better. A rainy or snowy day in April or May can produce outstanding dry fly fishing over these insects. The beauty of the baetis hatch is that is that the insects are so small that trout need to feed on large numbers of them before they are full. When a front moves through in April and rain is spitting throughout the day, the blue winged olives hatch in droves and fish will aggressively feed on the insects for several hours. The bugs wait until after noon to appear so there is no need to hit the river too early. A few different styles of baetis patterns are required to successfully fish the hatch. Before the emergence a small dark colored nymph such as a pheasant tail can be very successful. I also have had a lot of success with a fishing cdc style baetis emerger patterns deep before the hatch. This class of patterns was designed to be fished just below the surface film, but they are also very effective fished behind a split shot through deeper runs. As the hatch progresses and fish begin to focus on the surface there is often fish targeting both duns and emergers or cripples. Instead of trying to determine if a trout is on a dun or emerger, I prefer to fish a two fly combination with a either a thorax style dry or a bent hook dry with a zelon shuck that dangles below the surface on top and a cdc emerger fished a few inches below the surface as the second fly. Trout in Montana aren't very wary early in the season after a long winter of dormancy and they will eagerly take a well presented imitation during the hatch.
Another important mayfly hatch that occurs few weeks after the baetis first appear is the March Brown. March Browns are much larger (size 12) than blue winged olives and often bring large trout to the surface. The hatch is more sporadic than the often prolific baetis, and like the baetis they hatch in greater abundance on cloudy days. A large pheasant tail is a great imitation of the nymph and traditional Catskill dries in a brownish gray hue are the ticket for a surface imitation. One of the largest Montana trout that I have personally seen was caught by one of my clients in a side channel of the Madison during a march brown hatch. The 25" brown was greedily taking the naturals when we waded around a bend and it didn't hesitate to grab our imitation.
Baetis and March Browns continue to emerge until runoff begins sometime in the middle of May. The final significant spring hatch to occur is also the most prolific. The Brachycentrus order of caddis first appears near the end April and becomes gains strength throughout may until it is disrupted by runoff. The dark bodied caddis is commonly referred to as the "mother's day hatch" and occurs in such abundance on the Yellowstone, Madison and Big Hole that back eddies are often completely carpeted with the insects. The hatch is so explosive that it sometimes produces unpredictable fishing. Often the best action occurs while fishing caddis pupae patterns below the surface in the late morning hours. As the hatch intensifies, fish begin breaking the surface and it is time to switch to dries or a dry trailed with a caddis pupae emerger. When fishing a trailed emerger 12-18" behind the dry, it is common to receive 3 strikes on the emerger for every one on the dry. Some days the fishing is so productive that you can raise hundreds of aggressive trout during the hatch. Hookup rates are low due to the kamikaze nature of some of the takes, but the actions is exciting. Some days the hatch is so thick that the fish get gorged and go off the feed making for a frustrating site of millions of insects with few rising trout.
Spring fishing in Montana is ranks as one of my favorite times of the year to fish. The great hatches and consistent dry fly fishing combined help to shake off the winter blues. The tourist season hasn't started yet and the rivers are largely left to locals making. With the mountains still full of deep snow and the valleys slowly greening up, the scenery is often breathtaking. Throw in some hungry trout gulping down dry flies and it is easy to see why spring fishing gets so many local Montana anglers excited.