The Giant Salmonfly:

Fewer hatches evoke the same frenzy as the Giant Salmonfly. Fly fishers plan for years to witness the craziness of large trout smashing the surface-eating giant, sometimes over 2-inch, dry flies. It is a truly unique and amazing experience that draws anglers from all over the world.

The Giant Salmonfly or Pteronarcys California is the largest stonefly in North America. The nymphs live underwater for 3 to 4 years before crawling to the shoreline, where they will shed their exoskeletons and metamorphose into winged adults. The adults emerge prepared to mate and only live for about a week (crazy!). After mating, the females crash in the water ejecting the egg into the water.


We typically see the salmonfly hatch mid to late May on the Henry’s Fork of the Snake River and late June to early July on the South Fork of the Snake River. Every year is a little different and in our experience, we have found the magic temperature of the water to be 55-56 degrees for everything to start happening. Typically, when the water levels are higher and if the weather is not too warm, the hatch will move up river around 3 miles each day.

Timing the hatch can be difficult. There are so many variables that go into play for these bugs to come off and even prior to the adults flying, the fish can gorge on the nymphs. Having a flexible schedule is crucial if you want to witness this hatch plus you need a bit of luck, so you better rub that rabbit’s foot you got!

Is it worth it?

Yes and No? Hear us out…the reward of the salmonfly hatch is unmatched. The hatch brings with it the chance to sight-fish and dry-fly fish for huge trout. If you are looking for an incredible hatch to plan for, the salmonfly should be at the top of your list…BUT, big bugs = big boat/people hatch and big expectations. The salmonfly hatch is one of the first big hatches that happen after a long winter and it tends to draw quite a crowd. If you are hoping to find a little solitude on the river, this may not be the hatch for you. If you are planning a trip to fish the salmonfly hatch, know that there is a chance of missing it. Patience and perseverance are key, and with enough of both, you’ll eventually get the chance to experience the salmonfly hatch.

What Gear and Flies?

Best rods are 9ft 5wt or 6wts with floating line, 7.5 foot 3x leaders or 9 foot 3x leaders. The best flies to use Chubby Chernobyl Salmonfly #8, Morrish Fluttering Stone Salmonfly #6, Henry’s Fork Salmonfly #6. For an updated fishing report and to get all the flies you need stop by our Ashton Fly Shop or give them a call at 208.652.3008.