First off, it is important to understand that certain insects have 'regional' names that depict what they actually are. Sulphurs are a perfect example of this phenomenon in dialect. In the Ozarks, a small to medium-sized yellow mayfly is usually referred to as a "sulphur", but in other parts of the country, this exact same insect is called a Pale Morning Dun (PMD). Regardless of what they are called, this bug has a reputation for bringing very large fish to the surface, and they can be found in almost any coldwater fishery. On the other hand, a crane fly is always a crane fly, but they do vary in size quite drastically, depending on the particular river.
This hatch usually starts to show up on the White River in the middle to the latter part of April, but the timing of their emergence depends on air temperatures as well as the weather conditions. If the spring has been warm and sunny, look for sulphurs to start coming off earlier than they would than if temperatures have been cold with cloudy skies. Also, a brisk wind can literally blow the duns off the surface, which will abruptly put an end to the dry fly action. Sulphurs typically range from a size #14 down to a size #20, but on the White, the bigger varieties seem to work the best. Their bodies are normally yellow (but not always), and their wing colors range from clear to off-white. Sometimes, the underside of their body can be off-white, as well.
On the Norfork, sulphurs usually start hatching in the beginning of May if the water is low. Because the dynamics vary so much when comparing the 'Fork to the White, you will rarely see any sulphurs on the Norfork if there is any water running at all, except in a few slack water areas behind islands, and the fish don't pay much attention to them over there unless the river is dead low. Because the White is a much wider river that runs relatively slow in the pool sections when there are two to five generators in operation, it is common to see sulphurs blanketing the water in certain spots, even during relatively high flows. Unlike on the Norfork, quite a few fish will come to the surface to grab a sulphur on the White when the water is running, and it is very possible to have a good day fishing the surface during a myriad of different conditions on that river. Still, when most anglers think of fishing with dries, they envision working a soft riffle or run on foot, and the most productive sulphur fishing on either river is going to happen when the water is falling or dead low.
There are many productive spots on both the White and Norfork to get in on a sulphur hatch, and typically, the best zones are going to be away from the dams. Although there are exceptions, you will start to see more and more sulphurs on the White from Gaston's Resort down to the Narrows, and once you get to Wildcat Shoals, the dry fly fishing is typically prime all the way to Buffalo City. Although there have been instances where a heavy hatch of sulphurs started coming off in the Dock Hole on the Norfork, the real action normally takes place from McClellan's Shoal all the way down to its confluence with the White.
The sulphur hatch is just like any other mayfly hatch; which means fishermen need to expect the unexpected. There will be times where our trout will hit any fly that even closely resembles this insect with reckless abandonment, and there will also be periods when the fish will become somewhat selective. As previously mentioned, sudden brisk winds can blow almost all the bugs off the water, which will often cause the trout to move to the bottom to feed on nymphs. Another predicament occurs when the sulphurs only remain on the water for a split-second before flying away, and there will even be times when they will not even be on the water at all, but they can still be seen flying around. There are reasons for all this behavior, but for the sake of simplicity, the best situation from a fishing perspective is when sulphurs are coming off and end up staying on the water for a long time. If this happens, there will likely be fish rising all over the place.
The White River and Norfork Tailwater are not well known for 'masking' hatches, but it is important to pay close attention to how the fish are feeding, especially before a hatch is likely to take place. If the rises are such that you don't see any part of their mouth breach the surface (but you can see their body and fins), the trout are probably keyed-in on emerging nymphs. For this reason, look for mayfly nymphs near the surface in slow water, and if there are quite a few moving around, a dry/dropper rig is likely going to be the most effective setup. Although the bodies of the adults are yellow, the nymphs are brown, so keep this in mind during the fly selection process. A standard pheasant tail works well as a sulphur emerger in sizes #16 and #18, but don't be afraid to try a variety of different patterns.
As far as imitating the sulphur duns, any number of yellow or pale yellow mayfly dry flies will do the trick; White River Basin trout do not rely on adult insects for sustenance, so they rarely get overly selective during a good hatch. The key is to make sure that your fly is floating high on the surface, and you should be in business. It is not uncommon for sulphurs and caddis to hatch simultaneously, but these trout are extremely opportunistic, so they often feed on any adult insect that happens to be floating by - in a way, you can "pick your poison" on these rivers.
Many of the locals and guides have a special place in their heart for a sulphur emergence. This hatch is known for fooling some of the wiliest fish on both rivers, and sulphur imitations are relatively easy to see compared to the midges and Blue Winged Olives that are effective most of the year. It is difficult to plan a trip to the White or the Norfork just to fish dry flies, but if you do find yourself wading either river from late April through July, make sure that you come prepared. When the fish are 'on', it's possible to get a rise on literally every cast, and there are times when a sulphur dun pattern will catch more fish than any other fly in your box. Exceptional dry fly opportunities do not occur all that often in the Ozarks, but when they do, the surface fishing is as good as it gets.
Crane Fly Larva
Unlike sulphur mayflies that go through an entire aquatic lifecycle, crane fly pupa and larva actually emerge from wet banks before taking flight. For these reasons, fishing with crane fly nymphs and emergers doesn't often produce very well, as the fish rarely get a glimpse at these morsels. Our adult crane flies are about the same size as sulphurs, but they do have long long legs; in a way, they resemble a large, yellow mosquito.
Crane flies are extremely inept at flying, and this is their biggest downfall. It does not take much of a breeze to cause these insects to start cart wheeling on the water's surface, and at that point, they are an easy meal for the fish. There are very few crane flies on the White, but they are common in the catch and release area of the Norfork. It is easy to recognize when the trout are keyed-in on this bug because the rise forms will be aggressive and 'splashy'; similar to when there are egg-laying caddis bouncing on the surface.
On some waterways where the fish see a lot of crane flies, it may be necessary to tie a leggy pattern to fool the most discriminating of fish, but on the Norfork, almost any sulphur imitation will do the trick. The Norfork crane flies are quite small compared to the bigger specimens that are found on other river systems. Since the Ozark version is diminutive and is almost the exact same color as the sulphurs, anglers have the opportunity to basically fish two hatches at once. If the fish are slurping sulphurs, a dead drift presentation is the way to go, but when the breeze kicks up and crane flies start getting 'trapped' on the water, the only change needed is to apply some movement to the fly (skating). On many days, a simple sulphur pattern is all that is needed to effectively fish two hatches.
Thoughts on 2011
At the time of this writing, it is not clear whether or not there will be an abundance of dry fly opportunities this year, but regardless, if you are going to fish the White or Norfork from April through July, it is critical to have a good selection of sulphur (PMD) patterns. Hatches on these rivers are usually simultaneous, with caddis, midges and sulphurs all coming off at the same time, so any pattern that can effectively imitate more than one insect will make the dry fly fishing experience easier and more enjoyable. There is no reason to carry 1000's of flies with you when fishing the Ozarks - it is smarter to concentrate on stuffing your boxes with a bunch of the standards that will always work. The White and Norfork are not technical fisheries and the trout are feeding machines. Having the proper presentation that best imitates what the fish are feeding on is paramount than the actual fly used. This concept holds true for both nymph and dry fly fishing.