Jump in grasshopper population has trout looking up on Montana rivers and streams
This brook trout fell for a grasshopper imitation on a small tributary of the Beaverhead River on Saturday. During late summer hoppers move toward rivers and streams seeking green grasses on which to feed. They are a prime late-summer food source for trout. Photo by Ben Pierce.
Tall grass. Big bugs. Hungry trout.
It’s hopper time in Montana, and this season is an exceptional one for anglers.
Fly fisherman David Thompson of Bozeman caught the action on the Beaverhead River during a recent float trip from High Bridge to Barretts.
“We had probably the best fishing I have ever had on the Beaverhead for hoppers,” Thompson said on Tuesday. “I don’t think of it as a classic hopper river, but it got to where we’d see a long bank with a field not far away and the fish were for sure keyed in on it.
“I don’t know why, but for about an hour and a half it was crazy,” he said. “I bet I landed 20 fish.”
Fishing on the Beaverhead River, along with many other streams across Montana, is benefiting from a surge in the grasshopper population and sustained late-summer flows.
Kevin Wanner, Montana State University assistant professor of entomology, said grasshopper populations across the state are on the rise. He said the last big outbreak was in the mid-1980s, but that Montana has seen an increase in grasshoppers over the last five or six years.
The U.S. Department of Agriculture’s Animal Plant Health Inspection Service conducts an annual statewide adult grasshopper survey in August. The recently published 2011 survey data indicates high densities of grasshoppers across much of central and eastern Montana with sporadic high-density pockets along the Rockies.
“We went from one million acres with more than 15 grasshoppers per square yard in 2007 to 17 million acres with more than 15 grasshoppers per square yard in 2010,” Wanner said. “That gives you an idea of the magnitude of the outbreak.”
Wanner said cool, wet springs in 2010 and 2011 have suppressed the outbreak, but warm, dry conditions in the latter part of summer and early fall have kept the hopper population high. He said some areas surveyed by the department in 2010 showed grasshopper densities of 50-100 per square yard.
“Typically these outbreaks last three to five years,” Wanner said. “We have kind of gotten into the beginning of an outbreak, but it has been tempered by the cold weather. If we get warm weather next spring, the grasshopper population could explode.”
That’s a grim prospect for agricultural interests across Montana, but with so many bugs, trout – and anglers – are sure to take notice.
Fly shops from Big Timber to Dillon carry a wide variety of grasshopper imitations. Many patterns are now tied with foam. The Grand Hopper, Moorish’s Hopper and the Pink Pookie are popular and effective foam patterns.
Anglers who prefer flies tied with natural materials should try classics like the Parachute Hopper and Dave’s Hopper.
Thompson said putting some movement on his fly to imitate the naturals drew strikes on the Beaverhead.
“A little, teeny twitch definitely didn’t hurt,” he said.
Wanner said grasshoppers will migrate toward green grasses, often found along rivers and streams, as the heat of late summer beats down on the fields. An errant hop or a lick of wind is all it takes for the big bugs to end up on the water.
Hopper fishing should continue to be productive through September and into October.
“When we get the onset of consist frost and cool weather, the grasshoppers will die off,” Wanner said. “It is not a couple cool days and they are killed off. It is when that late fall cool weather sets in.
“Last summer, when we had a couple nice weeks in the beginning of October, in that situation they will stay active.”
Related posts:
- Montana State students announce formation of Gallatin Flycasters Club
- Big water on the Big Hole: Learning the hard way to fish one of MT’s finest rivers
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