Spring is a special time for anglers across Montana. As temperatures increase trout become more and more active and the fishing quickly becomes exciting and more diverse. The Gallatin River holds a special place in the hearts of many and is a popular spring fishing destination. With its proximity to Bozeman and Big Sky it is a favorite of both locals and out of state visitors. Spring is the most dynamic season of the year when it comes to fishing and conditions change rapidly from late March through May. At its start, spring can still have a very winter-like feel with low flows and cold water. By late May the air temps begin to feel summer like and the river swells with the melting snowpack. During the spring season the Gallatin progresses through the lowest flows of the season in March to the highest flows of the year during spring runoff. Fishing starts off strong in March and gradually improves until spring runoff really kicks in sometime in May. The Gallatin is deemed mostly unfishable during the peak of runoff until flows start to drop sometime between mid June and early July.
Early in the spring it’s possible that the Gallatin is still frozen from Big Sky south (upstream) to about Taylor’s Fork. Right at the intersection of Highway 191 and Lone Mountain Trail in Big Sky a spring feeds in that keeps the river downstream through the canyon free flowing throughout the winter. There is also a 2-3 miles stretch between Taylor’s Fork and Snowflake Springs that stays open all winter due to the warmer spring water being introduced to the river. Just a couple miles upstream of Snowflake Springs is the Yellowstone National Park boundary. Yellowstone National Park does not typically reopen to fishing until the Saturday of Memorial Day weekend. So if winter still has a hold on the Gallatin, fishing downstream of Big Sky offers the most fishable water and the water below Snowflake Springs offers another 2-3 miles. The water below Snowflake gets easily congested with anglers, which makes it a tough call being so far away from other fishable waters.
Once runoff kicks into full swing most anglers leave the Gallatin for more productive fisheries like local lakes, spring creeks, as well as the Madison and Missouri Rivers. That being said because the Taylor’s Fork is responsible for most of the sediment that enters the Gallatin fishing upstream of that confluence can sometimes offer better opportunities, especially after the park has reopened to fishing for the season. It is possible that the river below Taylor’s Fork becomes fishable again towards the very end of spring, but the river doesn’t typically start to fish well again until the very beginning of summer.
Early Spring (March through Mid April)
Early spring on the Gallatin is characterized by low flows and cold water. Fish are still holding in their winter time lies and trout are concentrated in deliberate runs with a bit of depth and slow to medium current speeds. The vast majority of fish will be caught with nymphs in the early spring and wintertime tactics still produce. When nymph fishing utilize some spring creek tactics such as lighter flourocarbon tippet for the clear water and yarn or New Zealand style indicators to detect subtle strikes. Fly selection doesn't need to be too complicated. Medium sized rubber legged stonefly patterns, egg patterns, smaller bead-head nymphs, baetis nymphs and midge larva should round out your early spring fly box. Make sure to have a few baetis and midge dry flies as well just in case.
As the days grow longer the bite window will increase but trout will still be most active in the afternoon hours. Although most fishing will still be subsurface, early spring midges will hatch on sunny days and if you’re in the right place at the right time you could experience hours of good dry fly fishing. In late March or early April spring baetis will arrive, which greatly improves your odds of finding rising fish. Although the baetis hatch grows stronger in late April, warm cloudy days in the early spring can produce BWO hatches that encourage trout to move to the surface. Although not found in large numbers there are some skwala stoneflies that also hatch in April, so blind fishing a Chubby Chernobyl or skwala pattern on the surface can sometimes coax fish to the surface.
Mid Spring (Mid April to Mid May)
Mid spring is a dynamic time on the Gallatin and coincides with the peak of spring hatches. The baetis mayfly, aka blue-winged olive, steals the show this time of year and makes daily appearances in the afternoon. Bright sunny days will generally result in a sparse hatch of BWOs, while cloud cover will kick off intense hatches of the diminutive mayfly and bring greedy trout to the surface. Anglers need to pay close attention to both weather and the USGS river gauges. Warmer weather can increase the metabolism of trout and kick of insect hatches, but if the weather is warmer than average early snowmelt can dirty the river and spoil dry fly fishing.
Although the river will rarely rise to levels that are unfishable, when the river is on the rise during warm spells it tends to kill the surface eat. The goldilocks scenario is average high temps in the high 50s or low 60s combined with a high overcast or steady drizzle; these are the days when the river level remain stable while BWOs explode off of the water producing epic match the hatch fishing. If the river is on the rise and murky don't head, just plan on switching over to streamers or a nymph rig. Increase your fly sizes when nymphing to stone flies, worm patterns and larger bead heads as the water clarity decreases from added sediments.
Late Spring (Mid May through early June)
Generally by late May the river is on a steady rise as temperatures continue to warm. This tends to put a damper on the dry fly fishing but nymphing and streamer fishing can still be productive. Pay attention to weather patterns and river flows. Often we will get some colder wet patterns in late May and early June which will slow the snowmelt and produce great fishing conditions. Fish can be caught during runoff on the Gallatin as long as the flows are stable and not rising to fast. Be cautious when wading and make sure to carry a wading staff and only enter the water on slower inside turns. Often the fish are right against the banks so make short casts with large flies. Nymphing with big stonefly nymphs, small streamers, larger prince nymph variations, a variety of worms will work best. Darker colored flies that stick out in the murky waters will usually produce better results. Fish a short stout leader and seek out the slower flows along banks or behind rocks where fish will be protected from the strong main river flows.
The Gallatin can be a phenomenal springtime fishery. There is no other time of the year when the river changes as quickly from week to week. Make sure to pay attention to weather and flow patterns so that you can cherry pick the best conditions. When you catch it just right the Gallatin can be extremely productive in the early season!