BILLINGS -- The Mothers Day caddis hatch is coming off on the upper Yellowstone River.

In this part of the trout world, that's big news for fly fishermen. It's the first major hatch of the year here and the trout go on a big feeding spree and hitting dry flies.

Some Mothers Day caddis have shown up on the Stillwater River as well.

As always, anglers are watching the May weather and making the most of their days before high mountain runoff begins and the streams blow out with high, muddy flows.

Walleye fishing is good on the Big Dry Arm of Fort Peck Reservoir, but mostly spotty elsewhere.

Here's this week's rishing report:

Ackley Lake: The rainbow trout are working the shorelines and bank fishermen are doing well with PowerBait. -- Don's, Lewistown.

Bighorn Lake: It's a varied bite with some trout, catfish, ling, perch and walleyes being caught in 20 to 25 feet of water. It's spawning time for walleyes. -- Pryor Creek Bait Company, Laurel.

Bighorn River: Fishing has been good to excellent, slower in the mornings, but great in the afternoons. Flows are up to 3,500 cfs. Midges and blue-winged olives are hatching and dry fly fishing is improving every day. -- Bighorn Fly and Tackle.

Boulder River: The lower river is high and muddy. Above Natural Bridge is clear and fishing is good. Small stonefly and caddis patterns are working. Beadheads, prince nymphs, lightning bugs and biot bugs are working. -- Rainbow Run Fly Shop.

Canyon Ferry Reservpor: Rainbow fishing has been good on the north end. The hottest spot for shore anglers has been off the Outhouse between the Dam and Yacht Basin. The rainbows are being caught on worms, egg sacks and flies. Walleye fishing is slow, with some action off the south dikes. -- FWP, Helena.

Castle Rock Lake: Largemouth and smallmouth bass are biting well. Jigs and minnows are your best bet. A few small walleyes caught. -- Minnow Bucket, Huntley.

Cooney Reservoir: Some trout and some smaller walleyes are hitting. A jig and leech is your best bet for walleyes. Nightcrawlers are working for trout. -- Pryor Creek Bait Company, Laurel.

Deadman's Basin: Rainbow trout and kokanee salmon are biting well. Most anglers are fishing from shore. Garlic marshmallows, worms and shrimp are working. No reports of tiger muskies. -- Super D, Ryegate.

Fort Peck Reservoir, Dam area: Haxby, Graves and Bell Point and Bear Creek are producing lake trout. Fishing has been very good down the Big Dry Arm. Big walleyes and a lot of them have been caught. Jigs and minnows or Lindy rigs and minnows are your best bet. -- Lakeridge, Fort Peck.

Fort Peck Reservoir, Hell Creek: Not a lot of guys fishing because of the wet weather. The northerns are starting to hit around Snow Creek and Sutherlin Bay. Lake trout are a bit hit or miss but it's starting to pick up. Walleye action is spotty. Stable weather is needed. -- Hell Creek Marina.

Gallatin River: Water temps are still cold, fish are holding in the slower deeper runs. Split-shot and double nymph rigs have been the ticket. Rubberlegs and golden stones have been working well. -- Montana Troutfitters, Bozeman.

Hauser Reservoir: Rainbow fishing has been fair while trolling green flatfish around Black Sandy. Lake Helena has been producing a few walleyes on crankbaits. -- FWP, Helena.

Holter Reservoir: Rainbow fishing continues to be excellent from both shore and boat. Shore anglers are finding success at the Holter Lake and Log Gulch Ramps while using egg sacks or olive-colored wooly buggers. Boat anglers are doing well from Oxbow to Holter Dam while trolling orange Rapalas. Walleye and perch fishing is slow. -- FWP, Helena.

Madison River: The lower river has one to two feet of visibility and a green tint. Cherry and Elk creeks are pumping some mud. The upper river has been pretty good some days and other days have been slow. The streamer fishing is starting to pick up. Little black caddis are starting to show up. -- Montana Troutfitters, Bozeman.

Missouri River, Below Holter: Pink stuff has been the main ticket, but some anglers are finding fish up on midges and we are strarting to see baetis hatching. Anglers working streamers are doing well and the fish are getting more active as the water warms up. -- Montana Fly Goods, Helena.

Missouri River, Fred Robinson Bridge: It's high and very muddy and rising. Paddlefish are being taken. Catfish, sauger and walleye fishing has slowed down. -- Don's, Lewistown.

Nelson Reservoir: Action is still pretty slow. Water temps are still cold. Walleyes are still spawning. -- Westside Sports, Malta.

Spring Creek: High and muddy and no reports of many fish being caught. -- Don's, Lewistown.

Stillwater River: It's high and muddy below the Rosebuds. Above, it's nice and clear and the Mothers Day caddis hatch is coming off in the afternoons. Nymphing is good with beadhead sparkle prince nymphs, red copper johns, pheasant tails and beadhead caddis pupa. -- Rainbow Run Fly Shop.

Tongue River Reservoir: Crappie action remains slow. Some nice northerns are being caught. Brandon Bradley, 13, of Sheridan, caught a 5.24-pound smallmouth bass off Camper's Point. Bass fishing remains pretty good. -- Tongue River Marina.

Yellowstone River, Huntley: Catfish action is picking up. The river has dropped and cleared. Cut bait is your best bet with some fish up to 12 pounds. No big numbers of sauger or bass being caught. The Yellowstone Catfish Challenge tourney will be held Saturday from 11 a.m. to 7 p.m. and the field has been filled. -- Minnow Bucket, Huntley.

Yellowstone River, Livingston: The Mothers Day caddis hatch is coming off. Try caddis dries, pupa and larvae. Streamers during the hatch are very effective as well. Fish will still eat your standard fare so don't ignore stoneflies, eggs, and assorted mayfly nymphs. -- Montana Troutfitters, Bozeman.