Trouts Journal

Five Tips for Fishing the Salmonfly Hatch

Ivan Orsic / May 25, 2023

With the end of May upon us, as a fly fisherman in Colorado, you have to start thinking about the next big hatch. And when I say big, I truly mean BIG. It's the Salmonfly Hatch on the Colorado River, also known as Pteronarcys Californica, which can grow as large as 50mm - quite big in insect terms.

This abundant protein source arrives at a dynamic time here in Colorado, typically coinciding with the beginning of our peak run-off. However, this can pose challenges due to high and off-color water. Additionally, as the colder snowmelt hits the river, the water temperature can decline, potentially stifling the hatch. These can be tough problems to deal with, and in most years, they can make it difficult to hit the hatch at the right time and in the right place. The good news is that the nymph and dry fly patterns you will be using are so large that even on off-colored and high-water days, you can still have a successful fishing outing.

While hitting this hatch right in Colorado is very challenging, you do have some advantages. As with most hatches, they tend to move upriver as the water temperatures start increasing upstream with warming ambient temperatures. So, if you miss it in one area, you can move upriver and try your luck in another spot.

If you happen to be too early or too high above the hatch, there should still be plenty of salmon fly nymphs moving about in the river. The fish will be looking for these in the weeks preceding the adult hatch. Lastly, we are fortunate that the insects hang around in the river for a few weeks after the main hatches. Although you may not witness the same abundance of insects flying and crawling all over, there will still be occasional hatching and plenty of nymphs in the river. This translates well into post-run-off dry dropper fishing with large dries and nymphs.

Given the difficulty of timing out this hatch, some of the guides and I have compiled some tips and tricks for fishing it. Without further adieu...our tips.

1. Clear Your Schedule

If you've heard me talk about float fishing the Colorado River and fishing this hatch, you may remember my strong recommendation to clear your schedule for the last couple of weeks in May and the first couple of weeks in June. Yeah, that's a lot of time, but this hatch is hard to predict most years.

Once you have the time off, make your way to the Colorado River. I mean, camp down there if possible! Start looking and fishing around State Bridge and work your way up, searching for active nymphs and hoping to spot a fluttering adult. Water temperatures will be crucial, and that's where it gets tricky. At lower pre-run-off flows, the water temperatures can reach the right zone. The hatch typically steadily progresses upstream as water temperatures continue to warm up to around 56º F.

However, as the daytime temperatures heat up, bringing snowmelt and cold water into the river, it can disrupt the hatch. What you observed the previous day may no longer be happening. With all these variables, you need to time it perfectly for the best dry fly fishing. Having those weeks off will allow you to watch the cold fronts move through Colorado and observe how they affect the flows and the salmonfly hatch's activity. If you can't be on the river during those weeks, the next best thing is to call your local shops daily, maybe even keep an eye on social media and be ready to drop everything at a moment's notice.

2. Get After It Early

Now that you've cleared your schedule and are ready for the hatch, here's a great tip from Trouts guide - Kaleb Orrock. He recommends getting after the hatch and fishing early. And by early, he doesn't just mean the daytime; it's about being at the front of the hatch as it moves up the river corridor. If you are too late on the water, behind the hatch, or right in the middle of it, you may find the trout uninterested and lethargic, having already gorged themselves on this large protein source.

If you're not getting any interest in your flies despite seeing numerous naturals all around, it may be best to head upstream a bit. The key is to have the bugs still present but be right at the leading edge for the best results. Similar to the caddis hatch, there may also be some benefit in fishing slightly behind the hatch, where a few bugs are still around and the trout have developed a hunger for them again.

3. Don't Be Afraid To Size Down

Here's a great point raised by Trouts Guide Sean Cowman that can help in many ways during this hatch. Sizing down can offer numerous benefits. By using a fly that is slightly smaller than the natural, you may attract more looks and interest from the trout. While it may appear that you've matched the natural's size, it may look significantly different on the water's surface.

Dry flies can create various profiles on the water, so if you're experiencing refusals or less interest, try downsizing. Another reason to size down for this large insect hatch is to reduce the chances of the fish missing your fly, but more importantly, to reduce the likelihood of you missing the hook set.

The large flies can easily pull out from the fish's mouth, and if this happens multiple times, it can become frustrating. Downsizing can often solve this problem. Lastly, using a smaller fly can make it more difficult for the fish to throw your fly during jumps or fights. Bigger and heavier flies tend to be dislodged more easily than smaller ones.

4. Try Something A Little Different

This tip was mentioned by Sean, Andrew, and Kaleb. When you find yourself fishing in the middle of a hatch with lots of activity from other anglers and many naturals on the water, sometimes fishing a pattern that hasn't been widely used can be the key.

While it's beneficial to read fishing reports and follow the recommended patterns, there's often truth in fishing a slightly different pattern from what everyone else is using. Change up your offering, whether it's a home-tied fly or something that deviates slightly from the popular choices. You'll be surprised how even a small variation can make a big difference.

5. Unweighted Droppers

Here's a great tip from Trouts Guide Andrew Contreras for fishing droppers during this hatch. While fishing with a single dry fly is always desirable, there are significant benefits to using a dropper in most situations. Salmonfly nymphs are quite large and can be quite heavy if tied with weight. This weight can be advantageous when fishing in the middle of the river with stronger currents.

However, Andrew recommends using an unweighted salmon fly dropper nymph. The salmon fly nymphs emerge by crawling to the shore and out of the water. The trout will follow the nymphs to the shallow waters along the banks, where you'll be targeting them. With a lighter nymph, you'll experience fewer hang-ups on the bottom, and it will be easier to swim and bounce your fly along the bottom. Additionally, the lighter fly will facilitate the swing of your flies at the end of your drift, potentially provoking aggressive strikes.

These tips can significantly enhance your salmon fly hatch fishing experience.

Remember to keep an eye on the conditions, be flexible with your tactics, and enjoy the thrill of targeting these magnificent insects and the trout that feast upon them. Tight lines!

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