Montana FWP is ramping up AIS checkpoint operations for 2026, and this isn’t bureaucratic busywork. The threat is real, it’s close, and the reservoirs you’re already penciling into your spring calendar are exactly the waters on the line.
This isn’t a conservation lecture. This is field intelligence that could determine whether your favorite walleye flat or trout shelf is fishable five years from now.
Which Montana Waters Are Currently Under Watch
No confirmed zebra mussel population has established in Montana — yet. But “not yet” is doing a lot of heavy lifting in that sentence. FWP’s AIS monitoring data consistently flags the Missouri River corridor as the highest-risk pathway into the state, and that corridor runs directly through Fort Peck, Holter, and Canyon Ferry. Sakakawea sits upstream in the same drainage basin that feeds Montana’s most productive reservoir fisheries. That’s not a coincidence. That’s a pipeline.
Fort Peck Reservoir, at 245,000 acres, is the most exposed. It sits closest to the eastern entry points where trailered boats crossing from North Dakota and South Dakota present the highest contamination risk. FWP has already intercepted watercraft at eastern Montana inspection stations carrying mussel veligers — the microscopic larval stage that’s nearly impossible to detect without lab analysis. Canyon Ferry, just east of Helena, draws heavy boat traffic from across the region and gets pressure from anglers who’ve fished multiple states in a single week. Holter Lake on the upper Missouri isn’t exempt either. Its connection to the broader Missouri system makes it a logical next domino if upstream waters get established.
FWP has also placed Tiber Reservoir and Nelson Reservoir on its elevated watch list in recent seasons, due to waterfowl movement and suspected unregistered watercraft crossings from mussel-positive drainages. Neither one is a household name outside the Hi-Line, but both sit in vulnerable positions on the map.
What FWP’s Mandatory Boat Inspections Actually Mean for You This Spring
Here’s the practical part. FWP runs mandatory watercraft inspection checkpoints across Montana from roughly April through October, with staffing heaviest during the spring launch window — the exact time you’re loading up for opener. Checkpoints on US Highway 2 near Havre, I-90 east of Billings, and US-191 near Malta are among the most active eastern corridor stations. If you’re trailering to Fort Peck from out of state, or even from eastern Montana after fishing South Dakota last fall, plan to stop. That’s not optional.
Inspectors are checking for standing water in livewells, bilge compartments, and transom areas — the places where veligers can survive for days after leaving infested water. “Clean, Drain, Dry” isn’t a bumper sticker at these checkpoints. Failing to comply can get your boat decontaminated on-site or held. Montana law requires all watercraft to stop at open inspection stations. Bypassing one isn’t a gray area — it’s a violation, full stop.
If you’ve fished any water outside Montana since last season — and that includes Wyoming’s Boysen Reservoir, which carries its own AIS concerns — disclose it at the checkpoint. Honestly, the inspectors aren’t there to hassle you. They’re there to catch the boats that aren’t saying anything at all. Be straight with them and you’ll be on your way.
Before you launch this spring, make sure your watercraft is registered with Montana FWP, and download the iMapInvasives app to report any suspicious mussel shells or fouling you spot on docks, rocks, or boat hulls near the water.
What Zebra Mussels Would Actually Do to Fort Peck Walleye and Canyon Ferry Trout
Let’s be direct about the consequences, because “invasive species bad” doesn’t quite capture what a zebra mussel establishment would mean for the fisheries you care about.
Zebra mussels are filter feeders. A single adult can filter up to a liter of water per day, stripping phytoplankton and zooplankton from the water column at a rate that collapses the base of the food web. For Fort Peck’s walleye — already a fishery FWP manages carefully through slot limits and harvest quotas — that means the forage base for perch, shiners, and ultimately walleye themselves takes a catastrophic hit. Lake Erie’s walleye fishery saw dramatic population swings after zebra mussels established there, and Erie had far more management infrastructure than Fort Peck does. In my experience watching what happens to big-water walleye fisheries when the forage base shifts, the damage takes a generation to sort out — if it ever fully does.
At Canyon Ferry, the concern shifts to rainbow and brown trout. Clearer water sounds like a win until you realize that clarity comes at the cost of the plankton those fish depend on. Zebra mussel infestations also accelerate aquatic vegetation growth and alter thermal stratification — both of which change where and how trout hold through summer. Your go-to structure stops producing the same way. Decades of hard-earned local knowledge get erased by a mollusk smaller than your thumbnail.
Then there’s the infrastructure cost. Zebra mussels colonize water intake pipes, boat motors, and marina structures. The economic damage to reservoir infrastructure in states like Michigan and Minnesota has run into the hundreds of millions of dollars. That cost eventually hits Montana’s recreation economy — and the fishing access that depends on it.
The short version for spring 2026: Stop at every checkpoint. Drain everything. Dry your gear for at least five days between water bodies if you can manage it. The walleye you’re chasing at Fort Peck this May and the trout you sight-cast at Canyon Ferry in June are still there because people before you took this seriously. Don’t be the boat that changes that.