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The New Scientific Angling, Trout And Ultraviolet Vision

A Book Review by Joe Cornwall

Reed Curry is the voice of the Over My Waders website and the Contemplative Angler blog.  Both sites are Fly Fish Ohio favorites and have been for a long, long while.  Reed’s output has always been insightful, sometimes incisive, and always entertaining.  Now he’s dropped a bomb on us by publishing a book that explores the last left-turn in fly fishing.  Subtitled Trout and Ultraviolet Vision, Reed’s opus prompts us to give careful, methodical thought to that which is invisible.  Or at least invisible to the angler.  It seems that trout, and by extension many of the species for which we cast a fly, have the ability to perceive details that lie outside the range of the human eye.


Once known as “chemical rays”, the ultraviolet portion of the light spectrum was first suggested in 1801 by the German physicist Johann Wilhelm Ritter.  He determined that invisible rays, just beyond the violet end of the visible spectrum, caused silver halide to darken.  Eventually that discovery was practically applied and the technology became known as photography. 


Further scientific inquiry determined that these light rays were part of a continuous electro-magnetic spectrum.  Today we know UV as the cause of sunburn and, fortunately for life, most of it is absorbed by the atmosphere's ozone layer before it reaches the surface of the Earth.  But enough makes it to the ground that it is an important, though invisible to us, component of the environment.  Curry presents a compelling argument for the case that certain creatures, trout among them, could have been prompted by the engine of evolution to adapt this high-frequency light to their own benefit.  This is where the fun starts.


The New Scientific Angling opens with chapters that, lightly and with a broad brush, overview the physical nature of ultraviolet light.  The author avoids writing a physics text, instead presenting practical and easy-to-comprehend difference between florescence and reflectance, and a compelling argument for evolutionary adaptation to elements of the UV spectrum.  There is much scientific precedence for this; it's well established that snakes can "see" in the infrared spectrum, and perhaps mosquitoes, too.  But to my knowledge, no one has asked this question in a logical manner of game fish.


The material has a few rough spots.  In particular there are references to the UV spectrum being “below” the visible spectrum (ppg 11), which is incorrect. The wavelengths are shorter, but the frequencies are higher.  Blue light (and by extension ultraviolet) is more energetic (hence “blue” headlights on performance automobiles) because of the nature of this frequency spectrum.  These little technical quibbles aside, the treatment is easy to understand and right on the money conceptually.. There is a simple treatment of how ultraviolet light might interact with the aquatic environment that begs for a deeper (no pun intended) treatment.  This introductory material is efficiently presented in the first 38 pages.  Then, on page 39, Curry lays out the meat and potatoes of the meal with a series of fascinating photographs that illustrate the appearance of insects, baitfish, flies and fly tying materials photographed in both visible and ultraviolet spectrums.


Over the course of the next eight compact chapters, the author manages to show something I’ve never before seen in a fishing book.  It becomes apparent upon examination that the flies we fish and the insects and forage we imitate may look very different to a trout, bass or bluegill than it does to us.  This work suggests that otherwise identical flies may appear quite different when viewed in the ultraviolet than they do in the visible light in which we, human beings, perceive the world around us.  And it suggests that maybe those differences explain why two anglers using superficially similar imitations may experience very different reactions from fish.


A lot of ink is devoted to the Royal Coachman and some of its variants, for example. Says Curry;  “I will now be so bold as to suggest that… the white, highly-UVR wing in conjunction with the UV absorbent peacock herl provides all the visibility and feeing triggers that a trout needs.  The key, then, to the perennial success of the Royal Coachman series of flies is its UV signature.  The might be said for the Coachman, Prince Nymph, and Zug Bug – all very “taking” patterns, all sharing certain UV characteristics.”


The author’s theories help to explain one of my own angling experiences.  When I lived in Massachusetts I would fish any fly so long as it had yellow in it. This was especially true for streamers.  But in Ohio I’ve found my “go to” color had gone.  Yellow hasn’t done much for me here.  I’ve often wondered why.  After all, a golden shiner or chub looks the same in the Ohio River valley as it does in the Hocomock and Taunton River watershed.  Now I wonder if perhaps this is due to a change in the ultraviolet environment brought about by a fundamental difference in the water.  In New England the places I fished had fundamentally clear water that was tea-stained by tannins.  In the Midwest, the places I fish have water discolored due to suspended silts.


To make the situation even a bit more complex, I’ve had some success in Ohio waters fishing a Mickey Finn.  But I’ve also noted that my most successful flies used a florescent yellow bucktail that is nearly indistinguishable in shade and intensity from an ordinary yellow… at least to my eyes.  Why?  What makes that bucktail so much more effective?  The New Scientific Angling draws the map to a potential answer.  Photographs in the book compare the UV reflective signature of, coincidentally, a yellow bucktail and a florescent yellow bucktail that are almost identical in the visible light spectrum.  But in UV spectrum they are as different as polished chrome and tarnished silver.  Maybe the stronger UV reflectivity of the florescent yellow makes the fly more visible in the Heartland’s turbid waters?  And maybe the nearly total absorptive profile of the standard yellow delivered a similar visible advantage to fish in the black waters of the Northeast?


In an exciting twist, Curry’s work suggests as many, or quite possibly even more, questions than it answers.  This is a book that begs to be studied and acted upon.  It challenges the pensive piscator to find new ways to combine natural and synthetic materials and create patterns that deliberately deliver UVR profiles that better match natural prey or angling conditions. 


The New Scientific Angling, Trout and Ultraviolet Vision is a wonderful addition to the angling lexicon.  This isn’t a book for beginners, nor for those of minor commitment to the sport. You won’t find new fly patterns and killer techniques guaranteed to produce the next time out.  Nor will the reader find here-to-fore unknown hatches of insects to emulate.  This isn’t that kind of book.  But if you love the puzzle that is fishing, The New Scientific Angling just made it bigger and more complex - and much more interesting - by introducing a whole new dimension that the serious angler can explore.  I think this is just the tip of the iceberg.  Kudos, Reed!


The New Scientific Angling, ISBN 978098408636 is available from Buckram Publishing.

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