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Missoula Tricos – Sunny Side Up

The trico is a purely American phenomenon. You can tell by the name. When the British named their mayflies, they used terms like Little Marryat and Greenwell’s Glory. We just shorten the latin name, Tricorythides! The trico has also been known by other names, like the Little White Curse. At size 18-20, it’s a small fly. We all take trico flies for granted, but John Geirach once wrote the greatest advance in fly fishing in his lifetime was not in lines or rods, but tiny hooks to mimic the small insects trout eat.

CDC Hi-Vis Trico Spinner is one of Missoula Fly Fishing Guides favorite flies for the Trico hatch.

Tricos begin hatching in early to mid-August, and last through September, depending on the weather around Missoula Montana. Tricos are a bridge between the excellent post run-off fly fishing and classic fall fly fishing. Tricos are an anomaly in the mayfly world. They are one of the few mayflies that react positively to the sun. The brighter the day, the better tricos hatch. Also, the spinners fall at the same time as the adults emerge. An exciting aspect of the hatch is the trico clouds that appear over the water. The mating insects and the spinners ball up above the water, flying in a figure 8 pattern. It starts about 10 feet above the river surface, and slowly descends. Be ready, because when the trico ball hits the water, the fish are feeding! Female tricos, with their white abdomen are easily distinguishable from the all black males. The multitude of choices for the trico can make fly choice a bit difficult. Adult, emerger or spinner, male or female. When everything is dropping on the water, it can be a tricky riddle to unravel.


But not as tricky as the Pale Morning Dun hatch. While there are a lot of insect stages on the water, the tricos are so small, and food sources so scarce at this time of year, the trout seem to be less picky. We have found that a male spinner is effective most of the time, and is our go to fly. Yes, you will find fish that will refuse it, and having a few different flies is always useful, but for the most part a size 18 and 20 spinner gets the job done.


Tricos are crawler nymphs, and are found in the riffles. This is where to start looking for the trico clouds, over the riffles. But trout rarely feed on tricos in riffles. Not enough caloric intake for the energy expended to feed in the faster water. So the best trico water is a riffle that opens up into a pool. The trout set up in the pools and feed on the tricos coming out of the riffle. This also explains why the spinner is more effective in pools. The adults are drying their wings, then leaving the surface, while the spinners are floating downstream in the last throes of life. The spinner is simply on the water longer.


In Missoula, the Clark Fork River and Bitterroot boast excellent trico water for fly fisherman. Those rivers are a little lower gradient and have more areas of slower water. While the tricos will appear on the Blackfoot River and Rock Creek, high gradients mean the areas where fish feed on tricos are limited. Once you’ve located fish eating tricos, on any Missoula river, you’re going to find them there as long as the tricos hatch. Tricos are very consistent, and the trout count on that daily meal. They emerge at the same time, in the same way, and the trout are almost trained to be there to eat. It’s one of the most appealing factors about the tricos, their consistency.

After working at the Missoulian Angler for almost 30 years, Ron Beck has invented some of the most effective flies we have seen. His Peacock Trico Spinner is one of our all time favorites. One of the many flies he teaches in his advanced Fly Tying Classes in the Winter months.


With the small size of the fly, it’s also a time for small tippets. Tricos demand 5 or 6X, so they float correctly on the water. A soft tippet material is preferable for this hatch. Our favorite is the Trouthunter tippet. Quite soft, and it also comes in half sizes, to provide exact matching with a bit of extra strength. The least effective tippet for tricos is Maxima. It’s such a stiff mono that it often impedes the flies natural float. It can be done, but there are other products that make it easier.

The favorite trico in the shop is the Peacock Trico. Invented by Ron beck at the Missoulian Angler Fly Shop, a serious trico fisherman, it has been honed to perfection by hours and hours of on water testing. The Missoulian Angler Fly Shop also carries Hi-Vis tricos that are a little easier to see on the water. The Missoulian Angler has the largest fly selection in town, so you know we’re going to have a trico pattern that will fill your needs and take fish.
With its consistent nature and scarcity of hatches, the tricos are an important summer occurrence for fly fishing in around Missoula, and provides excellent fishing during some of the hottest days of the year.

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