This fishing report is by Montana Angler and published on May 5, 2025:
The Boulder River near Big Timber and half way to Billings is on the rise but with the cold weather in the forecast, things will most likely drop and clear again. The water is still cold and many fish remain in the deeper holes and runs. Fly selection isn’t complex this time of year, with old standby’s like San Juan Worms, Girdle Bugs, and Pheasant Tail’s producing fish. Hatches haven’t been gangbusters the fish are still feeding during the warmer times of the day. Look for your deeper, slower water and you should be able to nymph em’ up.
Be sure to read our latest blog post on how to choose the best leader for fishing for trout: Choose the Correct Leader and Catch More Fish.
The Month Ahead:
The Boulder is a north facing drainage and tends to go into runoff a bit later than other area rivers. As the water warms and rises the fish will become more active and spread out. Nymphing is going to be the preferred technique until after runoff subsides.
Long Term Fishing Forecast:
Dry fly fishing will pick up on the Boulder as its hatches get going after runoff. Like the Gallatin, the Boulder has extremely cold water and tends to fish well all summer. Terrestrials become very important over here later in the summer.
