Last June, flooding in and around Yellowstone National Park upended the lives of nearby residents, damaging homes, ranch properties, and roads. It also damaged boat ramps and fishing access sites, and made some parts of the Yellowstone River unrecognizable to guides who have been fishing in the area for years.

But, from an ecological perspective, the flooding benefitted fish habitat. And for fly fishing guides, relearning the river, with its new gravel bars and channels, means there are some uncharted areas to look for fish.

Matt Wilhelm is a burly mid-westerner who's been guiding fishing trips on the Yellowstone for 20 years. On a recent visit to its banks on a private ranch near the town of Livingston, surrounded by snow-capped peaks, he points out some of the changes last year's flood brought.

"That is a new channel, that's a pretty significant channel right there," he said.

When huge amounts of water barreled through here last June, it cut a new pathway through what was grass and cottonwood trees.

"There were all sorts of new challenges," he said. "It was a brand new river in a lot of places."

Woody debris the flooding river deposited now overhangs the river, providing new habitat where fish can more easily hide

When the water receded, Wilhelm and his guiding friends hopped in a boat and set out to re-learn the river. Familiar sandbars were gone. Sometimes, they had to get out and pull their boat over freshly created gravel bars or navigate hazardous new whirlpools. They brought a chainsaw in case they had to cut through trees.

"A lot of people will just breeze past it and not drop anchor, but if you're willing to get out of the boat and explore these channels you can have some dynamite fishing," he said.

More than 400,000 visitors a year fish while they're in Montana. They contribute about $1.3 billion in spending.

Wilhelm guides around 50 clients a year on the Yellowstone River through his Yellowstone Fly Fishing School.

While he's excited to bring them to this new stretch of river, he hopes there are still enough fish to keep his clients happy. The floods hit right after Rainbow Trout finished spawning last year.

"Those rainbow trout eggs were just hatching at that time and what I'm worried about is if those fish got washed downstream or if they were injured or hurt or killed or all three," he said.

Scott Opitz, a fisheries biologist with Montana, Fish, Wildlife & Parks, says it's too early to say how the floods affected the Yellowstone River's fish populations, but he's not expecting devastation.

"In terms of the fish world, a big event isn't always negative. A lot of times it can be a really good thing in terms of moving and loosening up that stream bed, so that those areas can be used more efficiently for fish to spawn," he said.

Opitz says the fresh rainbow trout eggs were susceptible to damages from the flood, but there would have to be multiple years of losses to really put a dent in the population.

"The one saving grace with the Yellowstone and a lot of our other systems in Montana is that those fish aren't restricted to just spawning in the Yellowstone River," he said.

Last year was a once in 500-year flood event, but Opitz anticipates fish populations will follow historic flood trends on the Yellowstone River. There may be some declines initially, followed by a rapid rebound.

Opitz compares what happened with the flood to a wildfire event: there can be some negative impacts, but it's also a reset for the system that later brings rejuvenation.

Fly fishing Guide Matt Wilhelm says he's excited to get back out on the river this summer and look for fish in some of the habitats the flood created.

"There's no prettier place to be than on a river or a lake trying to catch a fish, just being outside it's a great way to earn a living and a great way to be outdoors at the same time," he said.

This year, the Yellowstone River crested in late May. It will likely be fishable by the end of the month, but with all of the sediment still there it might take a little longer for the visibility to be clear enough for good fly fishing.