PMD Hatch

I was on the river recently and was pleased to see a terrific PMD hatch. Yes, it’s that time of year when Pale Morning Duns hatch in droves and the fish are eager to eat them off the surface.

I looked back at previous posts and sure enough, I’ve written about these flies in late May since I started my RiverKeeper Flies website.

To refresh your memory, or for the new fly fisher, here is some information I wrote in previous posts.

PMDs, otherwise known as Pale Morning Duns, are an important hatch for fish and fly fishers. Generally, you’ll find these flies in sizes 16 – 18. The hatch begins in late May and will continue through September. 

PMDs have a pale yellow body and smokey gray (or dun color) wing. But their body colors vary and include shades of pale green, yellowish-tan, or a light reddish-brown. Look at the bug carefully. The underside of the insect is what the fish sees and the color is usually lighter than on top.

I normally use a Sparkle Dun to imitate the natural. I like the trailing shuck, as many insects get caught in their nymphal shuck. The fish seem to notice this effect and don’t have to hurry and eat them because they can’t fly away until shedding the shuck completely.

The other phase I like to imitate is when the wings of the PMD are stuck on the surface. I think that profile is why the RiverKeeper Soft Hackle Cripple works so well.

This fly was designed to imitate the cripple

Mayflies in general spend much of their life as a nymph, rummaging around the rocky stream bed. When it’s time to hatch, the nymphal shuck breaks open and an adult mayfly crawls out and becomes a dun. Hatching may occur underwater or in the surface film. The PMD breaks through the surface film and waits for both wings to dry as the fly floats downstream in the current. Now the mayfly flutters its wings and takes flight. Sometimes it lands on the water again, floats some more then flies away to nearby vegetation and wait to become sexually mature.

Here is a PMD found in a back-eddy that was stuck in its nymphal shuck.

Similar to breaking out of the nymphal shuck, the dun too sheds the skin as the thorax splits open and out crawls another insect with clear wings which is called a spinner. The body color of the Pale Morning Dun spinners range from tan to rust, hence the name “Rusty Spinner”.

Females fly into swarms of males to mate. Watch for birds flying above the river. That’s a tell-tale sign spinner activity is about to begin. After mating, the males drop into the water and are available to fish. You probably won’t see them, only the occasional sip of a trout and you’ll ask “I wonder what it took”? That’s the time to pull out a Rusty Spinner.

These are some of the flies I use to imitate PMDs. For other ideas, including nymphs, check out the Mayfly Fly Patterns page for more flies to imitate the naturals.

If you’d like to learn more about entomology, BugWater: A fly fisher’s look through the seasons at bugs in their aquatic habitat and the fish that eat them by Arlen Thomason is a terrific book I highly recommend about the most common bugs you will find on your local river.

Speaking about books, I’ve recently added the following book to the Links to Free Old Fly Fishing and Fly Tying Books. Be sure to check out the list periodically, as I continue to update this page when I find new treasures.

• The Natural Trout Fly and It’s Imitation by Leonard West (1921)

Lastly, I’ve added a Euro Nymphs section to the Fly Patterns page that captures perdigon and other popular Euro nymphs fished in our Central Oregon waters. These are flies I’ve found or taught to me by Jeff Perin (owner, The Flyfisher’s Place) and Bill Seitz. I personally haven’t fished all of them yet, but the ones I have are very effective.

Enjoy…go fish!