Spring Hatches Are Coming!
It has been typical spring weather - wet, sunny, cloudy, warm, cold, and windy. Basically something of everything and then some, and as a result I’ve had several fishing excursions put on hold by high streamflows and wind. Frustrating, but not surprising this time of year. But what the weather does do is give me a little more time to get ready for the day I actually hit the water and find conditions worth fishing. And there is plenty to get ready for. Spring brings on some of my favorite bug activity of the whole year with mayfly, stonefly, and caddisfly hatches all turning on. So, let’s take a look at what hatches one can expect and how one should prepare for them.
Mayflies: Blue-winged Olives and March Browns
To me spring means March, April, and May, and during this three month period there are two mayfly hatches that standout. The first is one you should already be familiar with if you have been on the water at all the last month or so. It’s the late winter-early spring hatch of blue-winged olives or Baetis. This is one of the best known and most written about mayfly hatches in the country, and for good reason. The hatch begins as early as early January and continues well into April on most Western streams. Some of the heaviest hatches occur in February and March, and with little competition from other hatches trout often really zero in on them.
The early blue-winged olives in my neck of the woods, meaning Oregon and especially central Oregon streams like the Deschutes and Crooked Rivers, tend to be a size 18. Colors vary, sometimes between males and females, and between streams. Typically hatching duns have bodies of brown or gray with some olive thrown in. Wings are a uniform slate gray. While I take a close look at their color I worry more about matching their size, so try to get a natural in your hand and compare its size with the pattern you’ve selected. If you can’t match size exactly, a pattern smaller than the natural is almost always better than one bigger.
Your patterns for this hatch should include some nymphs, emergers, duns, and spinners. Because this hatch is so widespread and important, tiers have come up with dozens of different patterns for matching each of these stages. Don’t let all these choices confuse you. From my experience simple impressionistic patterns work as well or better than more exact complicated ones. I particularly like sparse, slender patterns for this hatch, so if you tie your own flies don’t put too much material on the hook. I’ve included photos of the patterns I often use, but there are many other good options available.
The second spring mayfly hatch is the March brown. March browns, known to those who prefer Latin as Rhithrogena morrisoni, provide both good surface activity and frequent frustration. The frustration comes from the unpredictability of their hatches. For example, on one day I will run into an excellent hatch, but hardly a rising trout in sight, and then the next day - with seemingly similar conditions - there will be just a few duns struggling on the surface, but nearly every one getting slurped up by a fish. Of course when duns are on the surface but no fish rising, fishing nymphs will typically be your best choice. But even I have a hard time fishing nymphs when duns are floating by me, and I have a lot less compassion for trout that refuse to rise when naturals are on the surface.
March browns most often come in a size 14. The nymphs vary in color from dark brown to a rusty red. Duns have tan underbodies and mottled brown wings. Make sure you have nymph, emerger, and dun patterns ready to go. Spinner falls of March browns are a rare occurrence in my experience, so spinner patterns are not something I worry about.
Stoneflies: Skwala or Brown Willow Flies
In February and March you are likely to find a few, and possibly many, winter stoneflies still flying about. These are the small, size 14-16, dark brown to black stoneflies that hatch best in the winter. If you find good numbers of them and fish taking them by all means match them - a little dark elk hair caddis usually works. But from March through April the brown willow fly is the important stonefly hatch.
Brown willow flies sometimes get confused with golden stoneflies, but they belong to a completely different family (Perlodidae vs. Perlidae for golden stones). The confusion stems from the light tan to golden yellow colored nymphs that get almost as large as golden stones. Adult brown willow flies are much darker than golden stones, and their common name does a good job of describing them, for they are brown and are often found running around on streamside willow branches. The timing of the hatch even seems to coincide with the very first leaves on willows breaking out of their buds. There are only two North American species, both restricted to the west: Skwala americana and Skwala curvata. These species are so similar in appearance anglers need not worry about distinguishing between them.
Nymphs are hungry little predators that reach about one inch long when fully grown. Match them with pale yellowish-tan stonefly nymph patterns tied on size 10 or 8 2XL to 3XL hooks. Dredging these nymphs along the bottom of riffles in March and April can be a good thing to do. If you’re lucky though, you’ll find enough adults running around to get fish interested in dry fly imitations. A dark brown stimulator on a size 10 3XL hook makes an effective pattern.
It can be quite hard to tell just how abundant Skwala adults really are, due to their habit of running along the ground instead of flying in the air. Males have a good reason for staying grounded - their wings are often only half the normal length, making them useless for flight. Females have fully developed wings and can fly, but more often than not prefer to run around on streamside willows or the ground. After mating with the flightless males they will walk out onto the water to lay their eggs. Since you will see few adults in the air even when abundant, it’s easy to overlook them entirely. I suggest that if you see even a few adults out on the streambank, tie on a dry fly imitation and fish it near shore where there is good holding water for trout.
Caddisflies: Saddle-case Caddis & Mother’s Day Caddis
These two caddis both produce excellent spring hatches. The saddle-case caddis (genus Glossosoma) is the lessor known of the two, but I think it is the more important hatch. I think the main reason it gets less attention is that these guys are small - only a size 18 or 20. What they lack in size, however, they make up for in large hatches that extend over several months. I often see them first in February, but March and April is when their hatches really get heavy. They will routinely be hatching at the same time as blue-winged olive mayflies, so if your mayfly patterns fail to produce, you should definitely try a small pupa or dry fly to match these little caddis.
Pupa tend to be a pale tannish-yellow. They swim up from the bottom of riffles and trout will move up into shallow, fast choppy water to feed on them. A Leisenring lift (up-and-across cast so the fly sinks then raise the rod tip to bring your fly back up towards the surface), is my preferred presentation.
The other excellent approach is to use a diving adult pattern. Adults are dark gray and the females dive underwater and swim to the stream bottom to lay their eggs. This activity will generally occur in the mid to late afternoon. While it may seem unlikely, a little size 18 dark caddis adult pattern fished a foot or so below the surface can produce very well. Fish them with a standard wetfly swing in the tailouts and current tongues below riffles.
The second spring caddis hatch, the Mother’s Day caddis, is well known to most anglers. In fact many anglers plan fishing trips specifically to coincide with this hatch that typically occurs around Mother’s Day. On many streams though this hatch will start in early to mid April and last until after Mother’s Day.
This caddis is a case making caddis of the family Brachycentridae and genus Brachycentrus. Larvae live on the tops of rocks in moderate to fast riffle habitat. The pupa tend to be bright green with a dark band on their abdomen and run about a size 16. Adults are almost black in color and also about a size 16. For fishing you will need both pupa and adult patterns. The pupa swim up to the surface in the riffles where the larvae live, so focus your attention on this habitat. You will likely see trout slashing at the surface as they try to catch the quick swimming pupae. Adult females lay their eggs on the water’s surface rather than diving underwater like the saddle-case caddis. After laying their eggs they die spent on the surface. To cover the adult behavior you may need both a high floating dry fly for emerging adults and a low floating dry fly for spent females.
There you have it. Two mayfly, one stonefly, and two caddisfly hatches. If the spring weather keeps you off the water, take advantage of it by tying or buying patterns of these hatches. If you do you will be well prepared to handle fishing situations for the next three months, and beyond.
