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Blue Winged Olives Light Up Rivers Near and Far

By admin - Posted on 26 April 2018

Fly Fishing Report from Two Continents
Telluride, CO and Northern Patagonia, Argentina

April 26, 2018

Northern Patagonia

Between the valleys of the Chimehuin and Malleo rivers, an elevated steppe of grassland and rock escarpments offers habitat for red deer, wild boar, fox and an exotic array of birdlife.  Cattle range natural pastureland on the fringe, near the town of Junín de los Andes, where the Chimehuin sweeps to the south after its descent from Lago Huechulafquen at the foot of Volcán Lanín.  Buttes on the northern edge of this steppe rise above the Malleo, cutting a skyline which, from river level, appears much like that of the Lower Gunnison or Animas rivers in Southern Colorado.  The Malleo valley rises sharply on the north side, too.  This time of year, the sun arcs entirely within the scope of this ridgeline, rising completely above for less than three hours each day, dodging intermittently behind rock buttresses on the rise and fall.  Long shadows pervade the corridor.  Some sections of river are alight for less than an hour each day.  Sunny areas warm into the mid 60’s, awakening as hatching mayflies cue a lively food chain of bugs, birds and trout.  

Unlike trout in Colorado, Patagonia trout seem most active in full daylight under sunny skies.  Guides Lucas Rodriguez and Mark Lewis concur that cloudy, rainy days offer the slowest fishing, even during the season of “autumn olives,” in which American anglers expect the best mayfly hatches to occur in soggy weather.  

                    “Then the weather turned really nasty. It was perfect.”   -- John Gierach

Monday dawned clear and still, a wind forecast of 5 mph offering a 4-weight day in 6-weight country.  The access road for the Lower Malleo follows the north bank of the river from the highway bridge 20 km downstream to the Chimehuin confluence.  At 11:30 am on this mid-April morning, the near side of the river lay almost entirely in shadow.  A brief examination of favorite north bank runs revealed no rising fish and virtually no aquatic insect movement.  Nothing moved.  Gazing into the most promising pools from high atop riverside boulders, no orange or brown-tinged silhouettes suspended in the currents.  It was cold.  The south side of the river, though less than 100 feet away, had been awash in sunlight for at least half an hour.  Mayflies were visible from a distance.  Where there are mayflies, there are usually…

Along this stretch, the south bank is lined with slender willows, creating a picket behind which the stealthy angler may stalk fish.  Just beyond the willows, a steep dirt bank rises 5 feet to a narrow terrace that runs to the base of cliffs.  Walking the edge of this terrace, the angler has an irresistible view.  This is a straight and even run approximately 200 feet long, dropping to a depth of 5 feet just inches from the bank.  Seam lines are created by low hanging branches of large willows, but these big trees are few and far between, leaving plenty of room for the angler to brush aside individual willow shoots for casting room.  Stalked from the terrace, heavy trout are visible every 20-30 feet, suspended at varying depths under extremely subtle eddy lines.  Fish near the surface appear in full splendid color.  The darker the fish, the deeper It holds. 



It is early in the hatch.  Some mayflies take flight immediately after emerging to the surface, their upward trajectory seemingly unbroken.  Others appear unhurried, shaking free their nymphal husk, drying wings and allowing the breeze to flip them around on the river’s glassy surface.  Few of these go uneaten.  Deep lying fish rise 3-4 feet without hesitation for an adult blue winged olive.  These BWOs are approximately a size 16, larger than most fall mayflies.  From above, the visuals are riveting, but from casting position at river level the suspended fish are no longer visible.  Virtually every adult mayfly produces a rise, however.  The patient angler might spend an hour in this run, making no more than 10-15 casts, but raising a fish on most of them.  On this morning, fish were hooked on the first, third, fourth and sixth casts, all rainbows between 14 and 19 inches.  The takes were remarkably confident, the trout rising with their full body length parallel to the current, like a surfacing submarine.  One time after the next, the fly disappeared in a swirl of fins and flashing gill plates. 

Fly fishing is a sport of moments.  That was Monday, from noon-2:00 pm on the south bank of the Lower Malleo River. 

Home on the Gunnison

In terms of hatches, spring and fall can be mirror seasons.  Argentina’s Malleo lies at approximately 40 degrees south latitude.  The Gunnison runs just south of 40 degrees north latitude through the heart of Colorado.  It is mid-fall on the Malleo and mid-spring on the Gunnison.  Guess what’s hatching on the Gunnison?  In fact, Blue Winged Olives are a staple of spring fishing throughout the Rocky Mountains, from the Madison to the Green and the Frying Pan to the San Juan, but nowhere in Colorado do they arrive which such momentum as on the Gunnison.  

[Native son Jake Ames lands a spring toad on the Gunnison]




With the blue wings, every stretch of this storied river has erupted over the past month.  Spring hatches have coincided with dropping river flows, leaving every trout looking up for food.  Low water years may ultimately stress the trout population, but in the short term the fishing is more or less out of control.  Rising adult browns and rainbows may be found virtually every day from the recently opened East Portal to below the Gunnison River Pleasure Park.  Even in the chilly depths of the Black Canyon, trout are rising.  The fishing is truly in the top percentile of best we’ve ever seen on the Gunnison. 

[Parker Thompson in the Black Canyon]



It may fairly be stated that every river near Telluride is fishing exceptionally well.  The Uncompahgre, San Miguel and even the Dolores are enjoying stellar pre-runoff conditions, prolonged by a lack of melting low elevation snow.  Spring hatches are sparse on these rivers, but midges, a few blue wings and the ubiquitous micro “snow stone” provide the fish enough motivation.  Site fishing with dry flies for fish over 16” is the providence of the Gunnison, but nymphing with a wide variety of back yard patterns has been highly effective on the San Miguel and Dolores.  Remember the days in which a Prince nymph, Hare’s Ear or Pheasant Tail would catch most every fish in the river?  Those days are right now.

Due to its low gradient and micro aquatic insects, the Uncompahgre always requires more attention to detail.  Fish are feeding with abandon, but they maintain higher standards for a well chosen and presented fly.  This is the product of uniformity in their diet.  At Pa Co Chu Puk, there are only 4-5 significant hatches stretched through the calendar.  A fish eating Snickers bars wants a Snickers, not a Milky Way or a Kit Kat, nor a cucumber, raspberry, anchovy or potato.  

The Uncompahgre’s blue winged olives and midges are much smaller than the caddis and stoneflies found on the San Miguel.  It’s harder to make a small fly look natural in its presentation because our leaders tend to drag those little #18-#24 hooks.  A dragging fly is rarely taken, except when streamers or caddis emergers are deliberately swung to imitate a lifelike natural.  As a rule, smaller flies should be fished on longer, lighter leaders.  On the San Miguel, we’re fishing 9’ 4X leaders with the occasional 5X tippet running to a small dropper nymph.  Over on the Uncompahgre, you’ll want a 9’ leader with 5X and 6X tippets added for greater stealth.

That’s the rundown.  Now, here are some pattern suggestions:

San Miguel and Dolores

Prince variations, size #12-#18 (Psycho Prince, right, below)

Twenty-Incher, #8-#14 (photo, right)

Pheasant Tail and friends, #14-#18

Hare’s Ear, #12-#16

Guide’s Choice HE #12-#18

Soft Hackle PT #14-#18

SJ Worm #12-#16

Pat’s R.L. Stone #8-#12

Rainbow Warrior, #18

Military Mayfly #18

Extended Body Para BWO, #16-#18

Parachute Adams, #16-#18


Silhouette Dun, #18-22

No Hackle, #18-#22

Extended body Para BWO, #18-#22

Hairwing Dun, BWO, #18-#22 (photo, right)

Single Midge parachutes, #20-#24

Military Mayfly, #20-#22

Mayhem, #18-#22

Splitback emerger, #18-#22


Gunnison (Black Canyon and Lower)

Silhouette Dun, #18-22

No Hackle, #18-#22

Extended body Para BWO, #18-#22

Military Mayfly, #20-#22

Mayhem, #18-#22 (photo, right)

Splitback emerger, #18-#22

Pat’s R.L. Stone, #8-#12

Hare’s Ear, #12-#20

Pheasant Tail, #18-#20

Streamers (Sheila Sculpin, photo, right)


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