Which Fly?

Stones (click image for detail)

Over time and through the history of fly fishing one of the constant and perplexing challenges facing the fly fisher has been matching the hatch.  In other words, creating imitative fly patterns that mimic the various stages of the aquatic and terrestrial insects that trout feed on.  On rivers, depending on the insect diversity, this can range from a very simple to a rather complex affair; an affair that truly makes fly fishing interesting, challenging and fun. Recently we closed shop for our annual road trip to the fabled waters of Idaho’s Henry’s Fork River.  Over the years we have chosen this river and waters similar to the Henry’s Fork because of the tremendous diversity of aquatic insect hatches they offer.  The dynamics of these hatches challenges our skills in a variety of areas, however none more than our ability to match them.

Spring creek waters, such as Idaho’s Henry’s Fork and Silver Creek, because of their variety and quantity of insects are some of the most difficult of fisheries to catch trout. These trout have so much food to choose from that trying to fool them into selecting your imitation of hook, hackle and hair over the tremendous volume of natural insects they encounter is an arduous task at best. It is a task that for many can be rather frustrating at times, yet very rewarding when solved.

A perfect example of this occurred the first morning of our trip to the Henry’s Fork.  Morning’s first light showed signs of good cloud cover to start the day off which is always a welcome sight when fishing to such educated trout.  We were on the water by 7:30am, earlier than most.  As we walked the well-traveled paths that parallel these fabled waters, millions of caddisflies of several different species swarmed above the rivers banks.  Mixed in with these caddisflies were black flying ants and several different types of mayfly spinners. For those that fly fish, it’s an amazing sight to see and the first signs of what lies ahead. 

Before moving further downstream we paused to take a closer look at the waters surface to see what insects may already be present.  A few spent caddis and mayfly spinners had already fallen victim to the rivers currents.  We also noticed that several smaller fish were beginning to feed selectively on the rivers surface. It wasn’t long before we found the first good sized trout engaged in taking breakfast from the rivers smooth yet complicated currents.  This is what we had come for. 

At first it was fairly easy to decipher what these first trout were feeding on, flying ants, since they were easy to spot on the water and not much else was present at the time.  However, by mornings end choosing the right pattern would become much more complicated.

Within the next hour of our arrival there were both rust and olive pale morning dun (PMD) spinners on the water, Flav spinners, Calliebaetis spinners, Trico spinners, and two species of spent caddisflies, all mixed in with the flying ants.  Now rather than a few insects littering the surface of the river, there were hundreds of thousands of insects.  By this time there were also a good number of very nice trout working this plethora of morning goodies.

So with all these different insects on the water, how does the fly fisher begin to decide which one to put on the end of the line?  Where does one begin? 

First off, know what to expect before heading out to the waters you plan to fish.  This is the first step to being successful and prepared.  In order to have the right fly selection you need to know what insects, both aquatic and terrestrial, you’re most likely to come across when fishing.  Since insect activity on rivers and streams where trout live is constantly changing, good current information is invaluable to your preparation and fly selection. 

If you’ve fished a river for a number of years you’ll already of gained some of this knowledge.  If you’re not familiar with the waters you’ll be fishing and the insects habits, get on the phone or stop in a fly shop or surf the Internet and find out what to expect.  Trout feeding habits during a complex or intense hatch situation can be very, very picky.  Having the appropriate pattern selection in the correct sizes and colors will be critical to your success. 

Next, spend a little time getting to know the various insects that inhabit the waters you frequent or are planning to fish.  Having the right pattern is only part of the equation.  It’s also critical to understand the lifecycle of insects that trout feed on in order to select the appropriate imitation.  Knowing the difference between a mayfly dun and a spinner or a pupa from an adult caddisfly is a valuable key in recognizing what trout are feeding on and selecting an effective imitation.

Another critical part of the equation is identifying rise forms.  Trout rise differently to not only different insects, but also to different life stages of the insects.  A good example is the caddisfly.  During a caddisfly hatch, trout will aggressively take the adults as they leave their pupae and fly away.  The rise form is often referred to as “splashy”.  However, when those same caddiflies return to lay their eggs, they will litter the surface of the water dying.  Trout, knowing that this stage of the insect’s life is an easy meal, will gently sip in a classic head and tail rise for the spent insects.  The difference in these rise forms is key to knowing what stage of an insect the trout are feeding on and part of the puzzle for selecting a fly pattern. 

Finally, here’s one more piece to the puzzle that will help in matching hatches. During times of complex hatches, when there are several different insects in various stages on the water at once, the number of rises will give another valuable clue as to what trout are keying on.  This time it’s not the type of rise form, but how many times a trout is rising in relation to the number of insects that are on the water.  Often times it’s assumed that trout feed on the insect that represents the largest volume of food in size or quantity when there are more than one type and stage of insects on the water.  The obvious doesn’t always hold true.

So next time you’re out and trout are rising all around your fly but you can’t seem to find a taker, put a little more thought into what’s taking place in the trouts world.  One of the great challenges and satisfactions in fly fishing is being successful during intense and complex hatches.   Putting it all together and solving the mysteries that these situations create will lead to some very satisfactory moments and fly fishing enjoyment. Steve steve@wrflyfisher.com
Western River Flyfishers http://www.wrflyfisher.com