Stoneflies are unique insects. They need high-quality water to survive and have a life cycle of four years. They can produce some of the most intriguing dry fly hatches of the year. It is necessary to understand their life cycle.
Earlier this week, we went over the Stonefly Life Cycle. If you haven't read it, we suggest you do so. It's a great precursor to this blog and will help you move forward.
Okay, all caught up? Great.
By the end of both stonefly readings, you should have a solid grasp of the stonefly life cycle and how to fish them effectively through all life cycles.
Sound interesting? Continue Reading Below
Most stonefly species are relatively poor swimmers, especially during their nymphal stage. Due to their poor ability to swim, nymphs will find refuge among the rock aggregate bottoms of river beds or lakes. While the nymphs are among the rocks, they will sustain themselves on the available vegetation or find other suitable prey. So what does this mean for the angler? Fish deep. When flows are relatively stable, stoneflies will often use their strong claws at the end of their–six–legs to cling to the surface of rocks or gravel at the bottom of a stream/river/lake bed.
The good news for anglers is that a simple weighted stonefly imitation is often the golden ticket to fool a hungry trout. Imitations such as a Prince Nymph with a tungsten or gold bead are great impressionistic stonefly nymph patterns and will produce fish to the net year-round.
When it comes to deciding where to fish stonefly nymphs, remember that they need high levels of oxygenated water to survive and mature. Because of this, stoneflies can be fished in fast-flowing riffles or along faster seams. It is also beneficial for the angler to use stonefly nymphs on deep long runs. If you are routinely tapping the bottom of the river bed with your stonefly nymphs, you know you are within striking distance of a hungry trout.
During the transitional seasons, water levels–especially tailwaters–can change instantly, and when this happens, the stonefly nymph is affected. So, what happens when the water level changes and begins to look more like chocolate milk? The simple answer is to fish heavier nymphs with a good amount of flash.
While the claws of a stonefly nymph can latch on tightly to about anything, stonefly claws are no match for the power of water. When snowmelt or storm runoff comes down the river, stoneflies–and other inhabitants–get jostled from their resting place and tumble downstream. As an angler, this is no time to fish the smallest-sized nymph in the box. Runoff is a time to be bold and throw heavily weighted stoneflies as obnoxious and loud as you can find or tie (Purple Umpqua Rubberlegs!). Remember that the fish are also fighting the increase in current, thus burning more calories, and a high calorie meal–like a Pat's Rubber Leg–is just what they are after.
During these times of high water, the river will be off-colored and murky. Make the fly selection stand out from all the others and opt for something with a bit of flash or UV dubbing. Often, that little sparkle is all a fish needs to induce a vicious strike ripping the bobber under the water.
When the time is right–seasonally–the stonefly nymph will start the emerging process. The timing of this emergence is often seasonal and occurs when the ratio of daylight and darkness is optimal for the stonefly.
When the nymph is ready to change into an adult, it will do so—depending on the species–in one of two ways. The “surface emergers” will simply swim to the water's surface and make their transformation just below it. The crawling emergers will crawl to dry land or river's edge through protruding rocks, downed trees, or low-hanging vegetation.
For the angler trying to imitate a “crawler,” getting a tight drift along the river's edge is ideal. Since the emergence of stoneflies is seasonal, trout will key into this and hold along the river banks waiting for an emerging stonefly to fall from the overhead vegetation. For the angler trying to imitate “surface emergers,” a lighter stonefly is optimal. Since these flies have removed themselves from the river bottom, using stonefly emergers higher in the water column will often produce better results. It is worth noting that fishing a two nymph rig covering both stages of the stonefly life cycle is another way to fish stonefly nymphs effectively through a section of water.
A Note On Fly Depth - There are a few ways an angler can cover multiple pieces of water with one fly rod. The use of a split shot, an anchor fly, or even a Euro Style nymph rig is a great way to fish multiple parts of the water column. If you are interested in Euro Nymphing and set up we have a great video series over on our Youtube Channel with Euro Legend, Russell Miller.
Now a land-dwelling insect, the newly formed adult stonefly will never return below the water's surface–willingly. Once the emerging nymph has removed its exoskeleton, it will allow the air to dry and harden its newly formed body and wings.
During this drying process, the adult stonefly will try to find concealment among the willows and vegetation, waiting until the time is right to mate. For the angler looking to capitalize on this fleeting time, it is as easy as throwing a–large body–floating stonefly imitation tight to the river bank where overhanging vegetation covers the water.
Large hatches are truly a feeding frenzy. However, before hatches occur trout will still be holding in those slower currents and deeper water zones. As the weather begins to warm so to does the water. The change in water temperature--among other things-- is a natural indicator for trout to start moving out of those low current zones and higher into the water column. When the hatch occurs, particularly stoneflies, it is not uncommon to see trout gorge themselves on this calorically dense meal–often so much that it leaves their intestines distended and bloated.
The stonefly life cycle is important to anglers and is one that can heavily dictate a day out on the water. While a stonefly's adult life lasts only a few hours, the nymph stage lasts for many months - this is why having appropriate stonefly nymph patterns and styles is important for the angler looking for a successful day.
For those looking to pick out stonefly nymphs for their next trip, opt for ones that are designed long and slender or short and stumpy. Anglers can effectively fish stoneflies through sizes 8 and 14; sizes 8 and 10 are a favorite during the stonefly molt in early spring. Stonefly nymphs are generally an earthy black, dark brown, olive-brown, gold, or golden yellow when it comes to color. As the stonefly nymph ages, the color of the nymph changes as well. While the specific colors of stoneflies vary there are a few common colors anglers should know, black with hints of reddish-brown to a dark olive-brown with yellow highlights, and finally an olive-yellow with a light yellow cream color. While some stoneflies begin their final molt in the early spring months, anglers eager to find success through a dry fly variation will find the best success from May through August.
I hope you enjoyed this overview of the stonefly. Stay tuned to the blog, where we will be going over other important insects. If you have questions regarding hatches, we have a dense selection of books perfect for any skill level. If you want to expand your knowledge on bugs, check out our Bugs for Beginners class hosted at our Denver shop location!
No matter your skill level here at Trouts, we want to ensure that your time on the water is well spent. That means we want to answer any questions you may have regarding hatches, flows, or where to fish this weekend.