Friday, March 4, 2011

Strategies for Moving Water

Note: This article was originally published in the October 2003 issue of California Fly Fisher Magazine.

Strategies for Moving Water
by Andrew Harris

As we fly fishers accumulate knowledge and experience on the water, we pass through alternating stages of rapid growth and stagnation.  We’ll learn a new skill that allows us to explore new kinds of water, then struggle for several trips or maybe several seasons until we make the next breakthrough in technique or understanding.  One of the most frustrating challenges occurs when an angler is first confronted with a type of stream that is significantly different from the water with which he or she is familiar.  For me, the frustration began when I made the leap from fishing small freestone streams to fishing spring creeks and tailwaters.  The yellow humpies and Montana stone nymphs that easily fooled trout on the tributaries to the Middle Fork Feather River would rarely tempt a fish on Hat Creek or the Lower Sac.
What I didn’t understand was that there were fundamental differences between these new waters and the freestone streams I was used to fishing.  The words “spring creek”, “tailwater”, and “freestone” were familiar to me from fly fishing literature but didn’t mean anything to me at the time.  I didn’t know how to identify which type of stream I was fishing, let alone how to adjust my strategy.  I was sorely in need of some simple guidelines to help me approach different types of rivers effectively.  
I’ve seen countless beginners struggle with the same principles while I’ve been guiding for Clearwater House on Hat Creek.  Over the past six seasons I’ve taught a course called Mastering the Art of Fly Fishing at least twenty times.  It’s a five-day course for beginning fly fishers.  One of the skills I try to emphasize when teaching this course is how to identify different stream types and make an informed decision about which flies and techniques to use.  In this article I’d like to expand upon this simple methodology.  It won’t hold true every time, but more often than not it will steer you in the right direction when confronted with a new piece of water!
Imagine that you’ve just driven up to a river that you’ve never fished before.  For a moment, forget about spring creeks, freestones, and tailwaters.  We’ll come back to those terms later.  Instead, let’s keep it simple.  The first question we want to answer is whether the fish are predominantly eating aquatic insects or terrestrials.  Why does this matter?  Let’s compare aquatic insects (mayflies, caddisflies, stoneflies, midges) with terrestrial insects (grasshoppers, crickets, caterpillars, ants, beetles, bees, flying termites, cicadas, jassids, ladybugs).  First of all, most aquatic insects have a one-year life cycle, the vast majority of which is spent underwater.  On the other end of the spectrum, terrestrial insects enter the trout’s world from the surface.  Some of them sink quickly, but most of them stay on the surface for quite a while.  Accordingly, trout used to eating terrestrials are more likely to be looking for food on the surface even when there is no hatch. 
Terrestrial insects also have a lot more action on or in the water.  Remember, aquatic insects live 99% of their lives in the water.  They fly out briefly to mate, and then come back to the water to lay their eggs.  Aquatic insects are not afraid of the water.  Other than bouncing on the water to lay their eggs, they don’t struggle very much on the surface.  The water is their home.  Terrestrial insects, on the other hand, have no intention of going swimming.  They only end up in the water due to a tragic accident like a gust of wind or a faulty foothold on a branch.  When they end up in the water, they try to walk, hop, or fly out.  Trout that eat a lot of terrestrials recognize these struggling insects, and are quite likely to mistake your poorly presented, skating Yellow Humpy for one of them.  To the trout that primarily eats aquatic insects, your skating Yellow Humpy will either not be recognized as food or will look quite frightening.
Terrestrial insects also come in a much wider variety of sizes, shapes and colors than aquatic insects.  Most aquatic insects are quite small.  If you get out your seine and sample the bugs in a productive stream, you’ll notice that most of the nymphs are less than half an inch long and are black, brown or olive.  Conversely, terrestrial insects come in many different forms.  In other words, terrestrial-eating trout are used to looking for buggy-looking food items of all sizes, whereas aquatic insect-eating trout are used to looking for relatively small food items that come in a limited number of shapes and sizes.
            In short, we now know that fish that eat mainly aquatic insects will want to eat smaller flies that resemble insects that are currently hatching (or otherwise in abundance).  Fish that mainly eat terrestrials will be more likely to eat larger flies and to eat dry flies even in the absence of a hatch.  The key to determining the make-up of the trout’s diet is the presence of aquatic vegetation (the fully-submerged kind, as opposed to emergent vegetation like tules).  Aquatic vegetation is common in spring creeks and tailwaters.  Let’s explore the characteristics of these two stream types.  Spring creeks are primarily fed by springs.  Water levels, temperature, and clarity are nearly constant throughout the year, so fish can feed heavily year-round.  The weedbeds form the base of an immense aquatic food chain.  Aquatic insects are the majority of the trout’s diet.  Terrestrials play an important role only when present in large numbers or when there aren’t big hatches of aquatic insects.  Since there is a lot of food available, spring creek trout are typically very selective.  When there is a hatch you’ll have to match it.  The fish will become very selective to whatever is available in the greatest abundance.  The good news for the angler is that there will be many large fish.  The bad news: leave your Royal Wulffs in your fly box – they probably won’t work here!
            A tailwater stream is one that comes out the bottom of a large dam.  They are similar to spring creeks in many ways.  Water temperatures tend to be cold and relatively constant, flows may fluctuate but are generally conducive to feeding year-round, and water clarity is fairly constant, if not necessarily very clear.  Tailwaters are very rich in nutrients because all the nutrients in the reservoir upstream get concentrated into the river below.  These nutrients jump-start the food chain below the dam.  Tailwaters usually have aquatic weeds and huge numbers of bugs and fish.
Significant aquatic vegetation is uncommon in freestone rivers.  Freestone streams are mainly fed by runoff from snow and rain.  The volume of water fluctuates drastically throughout the year, typically very high in spring and very low in summer and fall.  The temperature and clarity also fluctuate with the runoff.  Spring runoff tends to be cold and off-color.  In the summer the water is very warm and clear.  Terrestrial insects play a large if not dominant role in the fish’s food supply.  West-slope Sierra Nevada rivers such as the Feather, Yuba, American, Merced, and Tuolumne are prime examples of freestone streams.
            In a freestone stream, there just aren’t as many aquatic insects for the trout to eat.  Accordingly, freestone trout are generally more opportunistic and more willing to eat simply because they can’t afford to let food items pass them by.  They will also move farther out of their way to eat a fly than a spring creek or tailwater fish.  And since terrestrial insects are likely to play a larger role in the diet of the freestone trout, you might as well fish a relatively large fly (size 12 or larger) that will get their attention.
            What we’ve learned so far can be summarized as follows:  If your stream has no weeds, you might as well start prospecting with a large attractor dry because the fish are probably opportunistic.  Good choices would include a stimulator, yellow humpy, or royal wulff in sizes 10-14.  If that doesn’t work, try nymphing the deeper water with a large attractor nymph such as a beadhead prince, birds nest, hare’s ear, copper john, or pheasant tail size 10-14.  If your stream does have significant aquatic vegetation, don’t bother fishing dries unless you see fish rising, and in that case you’ll have to match your fly to the natural the fish are eating.  If no fish are rising, you should try nymphing with a small mayfly nymph like a pheasant tail or Mercer’s micromayfly size 14-18.
Sound simple?  Enter complicating factor #1:  the gradient of the stream.  To put it simply, are the fish rushed to make a feeding decision due to the velocity of the water?  A fish on the flatwater of Hat Creek, Fall River, or the Owens has all the time in the world to investigate your fly and decide whether to eat it.  These streams fit the definition of a “classic spring creek”:  a meadow stream with a very low gradient and very clear water.  However, many spring creeks have very high gradients.  The same is true for tailwater streams.  A fish on the McCloud River, which is by definition a spring creek and a tailwater, has a limited amount of time to make that same decision due to the velocity of the water.  The McCloud is a rough river with a very steep gradient.  Despite the fact that there are abundant aquatic insects and that the fish are well-fed, the fast-flowing water doesn’t afford the fish a lot of time to examine your fly.  A well-presented attractor dry can bring fish to the surface.  Larger nymphs also work well because of another manifestation of high gradient: stoneflies!  Large stoneflies such as salmonflies and golden stoneflies prefer the highly-oxygenated areas found in high-gradient streams.  The salmonflies have a three-year life-cycle, so large nymphs up to two inches in length can be found in high-gradient streams year-round.
            To revise, when confronted with a high-gradient section of river, chances are good that a large attractor dry fly will work.  However, if the river displays spring creek or tailwater characteristics, such as aquatic weedbeds (or large concrete dams), you might switch over to nymphs fairly quickly barring any dry-fly success.  Instead of the larger nymphs (size 10-14), you might try some smaller nymphs (size 12-18) that are more likely to imitate the smaller spring creek bugs.  It’s all about seeing what you can get away with.  If I think I can bring up a fish on a dry, I’ll try it.  I think a fair number of anglers err on the side of caution when approaching new water.  They automatically start with a nymph rig even on water where fish will rise opportunistically to dry flies.  I’ve also noticed a lack of dry fly skills in the general angling populace, and my theory goes something like this:  indicator nymphing works so well that a lot of anglers become proficient with it and catch so many trout that they stop fishing other methods. Why mess with success?  My answer: I like to see the fish eat the fly.
            Whether you want to see the fish eat the fly or just see the indicator go under, you should read on, because there are two more factors to take into consideration when approaching a new piece of water and trying to figure out what to do.  The next most important consideration is the depth of the water.  If you have two trout and one is holding in shallower water, the shallow fish is more likely to come up and eat the dry simply because it isn’t as far out of its way.  Let’s say you’ve found a small, shallow spring creek with a lot of aquatic vegetation.  Nothing is hatching and no fish are rising.  A dry is still worth a shot just because the fish don’t have to move very far out of their way to eat it.  If that doesn’t work, try a dry and dropper rig.
            A final consideration: do the fish get hammered or have you just found the ultimate secret spot?  If you’ve found that secret spot (believe me – there are plenty of lightly-fished streams in California), fish will probably eat whatever you throw at them, so it might as well be something that floats well and is easy to see!

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