High, but not too high. Clear, but not real clear. Those are the river conditions that salmonfly lovers dream about on the rivers of southern Montana at this time of year.
The big bugs are already out on the Big Hole and lower Madison rivers. Soon, the hatch will pop on the Gallatin and Yellowstone, as well.
The annual appearance of this species of giant stonefly is a fly-fishing event to remember. The adult bugs hatch after being in the river as nymphs for three years, triggered by day length and water temperature. They emerge as insects as long and nearly as big around as your little finger.
For a trout, that's a huge and delectable meal.
"The optimum conditions for a fly fisherman is when the river is high enough so that the water is in the vegetation on the banks," said Dave Kumlien, a Bozeman outfitter and 30-plus-year veteran of fishing the hatch.
"The trout will follow the migration of the nymphs in toward the banks. They'll feed on them as they migrate. They'll feed on them as they're crawling out. Then when they're hatched, they'll feed on the ones that fall into the water," he said.
"The emergence of the adults requires those salmonfly nymphs to get to vegetation like willows where they can grab hold and split the case," Kumlien added. "They need to be holding on to something to get the leverage — a branch, a rock, something.
"If the river levels are low, and it's a long ways from the water to the vegetation, the hatch is not as good. Plus," he said, "that low water puts the fish far away from the bugs and they won't drop out of vegetation into the water."
Water clarity is also an issue, but the normal, summertime, crystal-clear flows of a trout river are not necessarily an advantage. With the hatch typically coming in the later stages of big snowmelt runoff carrying muddy water downriver, clarity can be extremely variable.
"I don't like really clear water," Kumlien said. "I'm convinced that it's such a big, ugly bug that it's not good when the fish can really see them well. When it's clear, the trout don't hit them as well.
"Also, the fish don't need much visibility," he said. "I floated the Yellowstone once when it was just plain brown. I doubt you could see six inches. And we slaughtered fish on dry flies. It was crazy.
"It proved to me that these fish don't need a lot of visibility," he said. "The fish are all in there close to the bank. It's a tremendous concentration of fish feeding on that hatch. They don't need to see far to eat these big bugs."
With water high onto the banks and all the action of nymphs in the water, nymphs crawling out of the water, insects in the streamside bushes and adult insects dropping into the water, all the fishing is within a few feet of the banks.
So fly fishermen cast to the banks with nymphs and big, floating salmonfly imitations. It's a game of casting accuracy to get your fly right to the water's edge or right under the overhanging willows.
"You pound the banks," Kumlien said. "People have to plan on losing flies. If you try to protect your fly box all day, you won't do well. You have to push your fly into the tight places — under bushes and in the pockets.
"I pay close attention to the configuration of the bank," he said. "The willow banks with bugs in them are good and the first open water below the bushes is also a good spot because those flies that fell in under the bushes have floated over them there."
Kumlien fished the hatch on the Big Hole twice in the past week with his sons, fishing the stretch from Divide to Glen. He said he hit the hatch about midway between Divide and Melrose.
His sons Kris and Kevin and Josh Cavan fished the lower Madison River in the past week, as well. They found salmonflies working their way up into Beartrap Canyon.
With the hatches moving upriver each day as water temperatures warm toward the upper reaches, these rivers should be offering good salmonfly action in the next few weeks.
The big bugs hadn't appeared on the Gallatin or Yellowstone when I talked to Kumlien Monday, but action on those rivers typically comes just a bit later than the Big Hole and Madison.
Kumlien said he has followed the hatch on the Yellowstone up into Yellowstone National Park clear past the Fourth of July in some years.
"There is still a lot of good salmonfly fishing to be had," he said. "The Yellowstone River now is still at the dangerous-to-fish stage with flows being so high. You can't do much fishing until it gets down around 6,000 to 7,000 cubic-feet-per-second, so people should check the flow charts. The Gallatin is still pretty high, but it's dropping.
"You want higher water, with at least a little bit of color," Kumlien said. "But not so high that it's dangerous. And if you're fishing it right, and casting your flies in tight in those pockets under the willows, be prepared to lose a lot of flies — and perhaps catch some big fish, too."
"The real attraction of the salmonfly hatch is to take the largest fish in the river," he said. "Some of the really big ones will feed on top — because it is a big piece of food. It's a great hatch to fish."
Mark Henckel is the outdoor editor of The Billings Gazette. His columns appear Thursdays and Sundays. Contact him at 657-1395 or at firstname.lastname@example.org.