After the Yellowstone River flooded last June some anglers were worried that fish populations would be decimated. While biologists are still trying to get a full picture of how the fish were impacted, early indicators are not showing catastrophic losses.
Every spring Montana, Fish, Wildlife and Parks inventories fish populations on the Yellowstone River. The agency operates long term trout monitoring sites at Corwin Springs near Gardiner and Mill Creek just south of Livingston.
In the first count since the flooding, FWP Biologist Scott Opitz said there were actually some increases to Brown Trout at both sites. Rainbow Trout and Yellowstone Cutthroat Trout also increased at Corwin Springs, but at Mill Creek were down about 20 percent and 36 percent respectively.
“Some of the changes we’re seeing in numbers of fish in different areas of the river are maybe just driven by changes in habitat, so different habitat types that used to be within the reaches we’re monitoring may no longer exists in those sites right now and we expect that to transition a little bit more this year,” he said.
Opitz said last year after the flooding biologists were worried about potential impacts to rainbow trout in particular because the flood came through right after they laid their eggs in the riverbed.
“Last year’s crop of rainbow are still too small to show up in our surveys, so that still could be the case. 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 itself; actually a lot of our Rainbow Trout not only spawn in the Yellowstone but use a number of our tributaries,” he said.
Opitz added that there would have to be multiple years of losses to really put a dent in the rainbow trout population.
Even though last year’s flood was larger in magnitude, Opitz anticipates fish populations overall will follow historical post-flood trends on the Yellowstone River where there may be some small declines initially, followed by a rapid rebound over the next 3-4 years.
