April Fishing on the East Gallatin River

April weather, stream flows, and summary

The East Gallatin River begins in the Bridger and Gallatin Mountain Ranges. Because these two ranges are large catchment areas for a massive amount of snow, the beginning of snowmelt runoff is the driving factor on fly fishing the East Gallatin River in April. If snowmelt runoff is slow to start, then the East Gallatin River is one of the area’s best rivers. However, if April sees warm air temperatures or precipitation, snowmelt runoff begins and fishing is very challenging. 

Weather on the East Gallatin River in April covers a broad range of conditions. Early in April the average daily high temperature rarely tops 55 degrees F, but by the end of the month the average daily high temperature rises to almost 65 degrees F. April receives an average of 1.2 inches of measurable precipitation, with half of that falling as snow and half falling as rain. 

Stream flows in April can be relatively unpredictable due to the possibility of changing weather conditions. For the first part of the month, if cold weather persists, the majority of the high mountain snowpack remains frozen. Because of the snowpack staying frozen, the first half of April rarely sees the river become muddy or too high from snow melt run off. 

However, the second half of April can be a wildcard should warm weather or rain persist. If daytime high temperatures rise above 70 degrees F and nighttime lows stay above 32 degrees F for more than a few days, snow melt runoff commences on the East Gallatin River. When this occurs, it is time to forego fishing until runoff subsides in early June. 

The East Gallatin River flows through Gallatin Valley—one of the more populous valleys in Montana. Fishing from a boat is not allowed so the East Gallatin is a walk-and-wade only fishery. Access to the East Gallatin is surprisingly abundant, however many landowners are diligent to limit an angler’s ability to stay within the streambed. To avoid any potential conflicts it is imperative all anglers on the East Gallatin River known the Montana Stream Access law and strictly adhere. 

April fishing: what to expect

April on the East Gallatin River covers all the bases—both for the good and for the bad. Weather will dictate hatches and the condition of the river and fishing be quite good or nonexistent. Because April in the Gallatin Valley can see days of sunshine, rain, and snow, fishing on the East Gallatin River means variety each and every day. 

For anglers desiring dry fly fishing, hatches of Blue Winged Olives (BWOs), skwalas, March Browns, and some caddis can occur. Various conditions need to line-up for the strongest hatches to happen, but similar to streamer fishing on the East Gallatin River the best way to fish dry flies on the East Gallatin River is to commit and hope for best. Choose appropriate dry flies to match the desired hatch.

BWO mayflies will be size 16 to 20 and be sure to have plenty of parachute dry flies such as Purple Hazes or Parachute Adams. 9-foot leaders with 4X tippets are the standard. Fish can be surprisingly selective on this freestone, so tapering down to 5X may be necessary. 

For tandem nymph rigs choose size 10 stonefly nymphs and size 16 beadhead caddis or Pheasant Tail nymphs on 7.5-foot or 9-foot leaders. Fluorocarbon leaders and tippets are best and expect to start the day fishing subsurface.  

If fly fishing the East Gallatin River in April, to catch the largest fish it is best to fish streamers. For streamer fishing choose size 2 to 6 streamers in olive or yellow/brown. A sink-tip can be an important addition to any rig. Slowly-stripping or dragging streamers through deep, slow runs or pools will produce more than fishing shallow flats or 4 to 5 feet-deep runs. 

Where to find April trout on the East Gallatin River

As the window for consistent fly fishing on the East Gallatin becomes more and more variable as April progresses, finding trout on the East Gallatin is more about having a river that is fishable than finding trout. Once snow melt runoff begins, typically later in the month or early in May, fishing becomes challenging. Prior to snowmelt runoff, hatches of skwala stoneflies, Blue Winged Olive (BWOs), and an early Mother’s Day caddis can provide plenty of action. 

Before snowmelt runoff begins, trout will be found in slower currents. Focus on the rivers slower and deeper waters—places like inside bends, long runs, eddy-lines and foam seams around large rocks or other structure. These “softer” waters allow for trout to expend very little energy while having access to available food. 

If hatch a occurs, look for trout to move into feeding lies. In April, hatches BWOs will make up the bulk of the hatches. For BWOs target slower water near bankside structure or the tailouts of longer, slower runs. If caddis or skwala stoneflies hatch, fish may move to faster water, but because the water temperatures are still cold, even during a strong hatch expect to find fish in slower water.

If anglers desire some of the river’s larger trout, they should fish with streamers and should fish over-sized flies. Choose white, yellow, or olive streamers in sizes 2 to 6 and pick an articulated pattern for the most success. The East Gallatin River is home to plenty of brown trout over 20-inches. Fish deeper runs and pools and be prepared to cover plenty of water as the East Gallatin River is a walk-and-wade only river. 

Important April hatches

The East Gallatin River can experience some of Gallatin Valley’s most consistent hatches in April. If the right conditions occur, hatches of Blue Winged Olive (BWOs) mayflies, skwala stoneflies, Mother’s Day caddis, or March Browns can all hatch in strong numbers. March Brown mayflies and skwala stoneflies are sporadic but prospecting with a March Brown or a skwala pattern can entice a fish to rise. BWOs can hatch on sunny or cloudy days, but a cloudy, slightly rainy day can create a large emergence. 

On the East Gallatin River, March browns are not as prolific as BW0s. Like BWOs, March browns will hatch in greater abundance with overcast skies and during a strong hatch many of the river’s larger trout will rise to the most abundant species.  

As warm weather replaces cooler weather, caddis can hatch in prolific numbers, however the warm weather also means the possibility for snowmelt runoff and high and muddy stream flows. Most caddis will be size 14 and 16 and are tan bodied.

East Gallatin River fly box for April

Caddis pupae size 12 to 16

Caddis CDC emergers size 12 to 16

Caddis dry flies with dark grey or tan bodies in size 12 to 16; 

BWO dry flies size 14 to 18

BWO emergers size 16

BWO nymphs size 16

March Brown dry flies size 14 to 16

Skwala stonefly dry flies in size 8 and 10

Stonefly nymphs in brown and black in sizes 10, 8 and 6

Sculpin patterns in sizes 2 to 6

Streamers in white, yellow, or olive in sizes 2 to 6