Ramblings of a Catskill fly fisher

The trico hatch

Posted 8/10/22

One does not hear a lot of talk about the midsummer emergence of our tiniest of mayflies, the diminutive species we commonly call tricos. At least I don’t. Is that because I’m just so far …

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Ramblings of a Catskill fly fisher

The trico hatch


One does not hear a lot of talk about the midsummer emergence of our tiniest of mayflies, the diminutive species we commonly call tricos. At least I don’t. Is that because I’m just so far out of the mainstream of fly fishing these days? Or are there other reasons, like all the challenges these little flies cause for fly fishers?

In any case, these mayflies that taxonomists classify as the genus Tricorythodes provide one of the most consistent and long-lasting hatches of all the aquatic insects we find in the Catskills.

Emergence begins in mid-July and extends well into the fall. So what’s the story here?

First of all, trico hatches require anglers to use very small size-20 and -22 flies, to match the naturals. Using those little flies mandates a 7 or 8X tippet. Any leader larger in diameter will not work when fishing trico hatches or spinner falls.

Using that delicate terminal tackle presents its own set of problems, like wind knots, break-offs and tangles in the tippet.

On the positive side, today’s 7X is much stronger than a tippet of that diameter was not that long ago.

Tricos have a unique hatching process compared to other aquatic insects. Unlike most species of mayflies, emergence, mating, egg-laying and spinner falls take place within a few hours during the morning. Anglers who are out early enough may find some fishing for the emerging female duns. The males hatch before dawn; the females at dawn.

After the females hatch, molting takes place in the stream-side vegetation.

Once molting is complete, mating takes place in the air, over the water. If the light is right, it is not unusual to see a large “ball” of swarming tricos  completing the fertilization process.

When fertilization is complete, the males fall to the water, spent. That’s when the fishing begins. Once egg-laying is complete, the females join the males. The dead and dying flies will bring soft rises from hungry trout looking for the thousands of spinners blanketing the water.

Despite all the years I have fly-fished, it was not until I met Bill (Willie) Dorato years ago that I learned about the trico hatch. We had a camp on the East Branch, near Shinhopple. Up until that time, I was not aware of these little mayflies.

Bill explained the tricos’ life cycle to me, advising that spinner falls began when the air temperature reaches 69 degrees Fahrenheit. In my experience, that temperature occurs right around 9 a.m. If conditions are correct, anglers can expect about two hours of surface activity before spinner falls end.

Fishing a trico spinner fall can be extremely frustrating. Because there are so many spent flies on the water, our fly will be just one among hundreds, perhaps thousands, so the chance of a rise is slim.

Since that is the case, anglers can become impatient and start changing flies, believing their pattern is at fault when it’s not. Patience and accurate casting are required for success when fishing a trico hatch. In addition, anglers are reminded that it is better to pick one steadily feeding trout to cast to, instead of casting to different risers. That “shotgun” approach seldom works.

Anglers also need to keep in mind, with so many flies on the water, that trout move slightly up and down and left and right, to pick off the hapless spinners. So it is a good idea to watch a steadily feeding trout to see if there is a rhythm and pattern to its feeding. It is also important to note how many naturals are let go between rises.    

The last time I fished a trico hatch was on the Henry’s Fork River in southeastern Idaho. We were on the water early and there were several trout rising along the bank, feeding on tiny mayflies. As the morning progressed, I was fortunate enough to hook and land a very nice rainbow during that hatch. Later, and upon examination of one of the duns, I learned it was a female trico.

Fishing a trico hatch is not easy. It involves extreme patience, determination and very accurate casting, with a gentle presentation. I found that the few times that I was successful when fishing to trico spinners falls, presenting my fly across and downsteam to rising trout worked best.

By using that approach, a trout sees the fly first, not the bulk of the leader or fly line.

Trico hatches and spinner falls begin early in the day, last a few hours and extend for several months. The flies are consistent, and emerge every day like clock work. I’m told that there are several broods each year.

The biggest issue that I found while fishing trico hatches in the Catskills and the Montana Rockies is wind. If you are on the water with a trico hatch in progress and the wind comes up, the fishing is over.

So if you have the patience, casting skills and correct tackle, fishing a trico hatch can be extremely rewarding. Rising and hooking trout during that hatch means that you are an excellent caster, know your tackle and are determined. So if you don’t get blown off a river by the wind or put down a rising trout, it mostly comes down to whether or not your fly is the next fly.  

mayflies, tricos, fly fishing, hatching


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