April Fishing on the Montana Spring Creeks

April weather, stream flows, and summary

Three creeks—Nelson’s, DePuy’s, and Armstrong’s—are the trifecta that make up these world famous fisheries flowing near the Yellowstone River in Montana’s Paradise Valley. Each creek features subtle differences that can take years of fishing to learn and appreciate, but as a whole they all fish similar to each other in April. 

Because each creek’s stream flow remains relatively consistent year-round, the need to monitor stream flows is non-existent. However, external factors such as weather and wind are vital to how a day of fly fishing the Paradise Valley Spring Creeks will unfold. 

Weather in April is a mix of all four seasons—sunshine and bluebird days, rain and drizzly days, and a few days of snow and blizzard-like conditions. The potential exists for all of these to occur in the same day. Daily average high temperatures increase throughout the month, with early April seeing daytime highs in the low 50 degrees F and by month’s end the mercury rising to average in the mid 60 degrees F. Less than 1.5” of measurable precipitation falls in April, with less than .03” of that falling as snow. Armed with quality gear to protect from the weather, anglers fishing the spring creeks in April could experience some of the best fishing of the year despite variable weather conditions.

Wind can play a factor in a day’s fishing on the spring creeks. Because the ideal day on the spring creeks is shaped by a hatch of Blue Winged Olive mayflies, if winds in excess of 15 MPHs are forecast, many of the hatching dry flies are unable to stay on the water as they get blown off before a trout can consume them. Plus, long leaders that are essential for success are a little more difficult to cast. On windy days, knowledge of the creeks is essential, as plenty of sections exist that may be tucked away or out of the prevailing wind. 

The Paradise Valley Spring Creeks in April are one of the most consistent fisheries in the Bozeman area during April. There is no denying that experience and knowledge can lead to a better experience on these unique fisheries, but as other fisheries may be day-to-day prospects in April, the Paradise Valley Spring Creeks during April will be fishable while others river may not. 

April fishing: what to expect

Anglers on the spring creeks in April can expect strong hatches of Blue Winged Olive (BWOs) mayflies and consistent action with midges—but most midge action will be with subsurface flies. A typical day fishing Nelson’s, DePuy’s, or Armstrong’s spring creeks in April often begins fishing a shallow-water, sight-fishing nymph rig with size 18 or 22 midge or mayfly nymphs. Long leaders of 12- to 15-feet are best, tapered to 5X or 6X fluorocarbon tippets. Around mid-day the BWOs begin to hatch and anglers with moderate casting ability switch to targeting trout eating BWOs on the surface. 

A strong BWO hatch can last up to four hours, but most BWO hatches in April last around two to three. Like a well-written movie, a BWO emergence on the spring creeks will draw-in the angler and trout during the early phases of the hatch, then there will be a period of peak activity with plenty of trout rising to adults or emergers, followed by the easing of activity. Most BWOs on the spring creeks are sizes 18 to 22. Dry fly anglers should be armed with supple tippets in sizes 5X and 6X, plenty of quality floatant that works well with CDC, and the ability to execute a reach cast.

The spring creeks are home to massive populations of scuds and sowbugs. These aquatic insects do not hatch like a midge or a BWO, but in April spring creek trout gobble up these high-protein packed morsels on a regular basis. Sight-fishing opportunities abound on the spring creeks in April, so a tandem, shallow water rig on a 12- or 15-foot leader tapered to 5X or 6X fluorocarbon with a size 18 or 20 scud, sowbug or midge can produce fish. Most experienced spring creek anglers use small yarn or light pinch-on indicators and small size—6 to 12—split shot. Because most currents on the spring creeks run slower than larger rivers, less weight and shorter depths from fly to indicator are essential. Successful patterns include Wondernymphs, JuJu Baetis, Zebra midges, and WD-40s. 

Streamer anglers may find some success on the spring creeks in April, but most spring creek trout consistently eat dozens of small flies rather than a few larger flies. Think of them as foragers rather than predators. Generally speaking streamer anglers on the spring creeks choose a light color on a sunny day and a dark color on an overcast day, but the most successful streamer is sparsely tied and loosely weighted. 

April sees many rainbow, Yellowstone cutthroat trout, and cutthroat-rainbow hybrid trout still spawning or recovering from spawning. All three of the Paradise Valley Spring Creeks are important spawning habitats for Yellowstone River trout. To ensure the long-term health of the Yellowstone River’s trout populations do not target actively spawning trout or trout near redds. Be extremely cautious while walking-and-wading and avoid walking on redds or fishing in the vicinity of redds. Redds are sections of small, cobble in the stream bed cleared by spawning fish. Additionally, if a spawning or spawned-out trout—skinny, dark in color and has the appearance of looking beat-up and tired— is caught, please release as quickly as possible.

Where to find April trout on Nelson’s, DePuy’s, and Armstrong’s spring creeks

If a hatch of Blue Winged Olive (BWOs) mayflies doesn’t occur, most spring creek trout will be in deeper water. On the spring creeks “deeper water” typically translates into any three to six feet deep depression or bucket that is near a shallow flat or riffle. In April this deeper water provides plenty of food—remember food is abundant on the spring creeks—and cover from overhead predators.  

Even in April with water temperatures in the 40 degrees F, trout on the spring creeks will seek out food that is subsurface. In this deeper, slower water, fish are probably eating midges, scuds, sowbugs, or mayfly nymphs.

Because the spring creeks are loaded with food, any small change in depth or break in current can create a holding lie, which can quickly become a feeding lie if BWO nymphs become active prior to a hatch. If fish are not rising or actively feeding near the surface, it is highly likely they are still feeding. Target any change in current speed or change in depth, such as a bucket or small depression where the depth may be a foot or so deeper than the nearby bottom structure. Plus, with the crystal clear water of the spring creeks, sight-fishing is a daily occurrence, so be prepared to actively pursue specific fish—it just may be with shallow, lightly weighted nymph rigs rather than the large indicator rigs so common on larger rivers. 

As the month progresses and hatches of Blue Winged Olives increase trout will follow the food source. When a hatch is strong they migrate from slower, deeper lies and can be found in a variety of habitats. As each day can bring unique weather, the fishing action on a day-to-day basis is unique as well. Before noon most fish will be found in slower, deeper water and then as a hatch begins the fish will adjust their locations based on the available insects. 

When a strong hatch occurs, look for fish in slow current seams, on shallow flats, a slow seam next to a fast seam, any shallow water adjacent to any deep water, eddy lines, and seams behind rocks or seams created by faster water being slowed down by slow water. 

After a few days of warm weather and consistent hatches of BWOs, many spring creek trout may lie near the drop-off of a long riffle just before the water enters a deep run. Well-presented shallow-water tandem nymph rigs can rack up trout numbers in these subtle drop-offs below a riffle. However, dry fly anglers must be patient because most spring creek trout often require a thick hatch to migrate out of these safe holding and feeding lies. 

It also very important to know the spring creeks are all vital spawning habitat for many Yellowstone River trout. Rainbow trout, Yellowstone cutthroat, and cutthroat-rainbow hybrid trout will migrate from the Yellowstone River to spawn in April. Be extremely cautious while walking-and-wading and avoid walking on redds or fishing in the vicinity of redds. Redds are sections of small, cobble in the stream bed cleared by spawning fish. 

Important April hatches

April hatches on the Paradise Valley Spring Creeks are fairly consistent from year to year. Because the creeks originate from springs bubbling up from the ground, water temperatures at the source remain consistent every day. Daily high air temperatures and the amount of prolonged direct sunlight determine if a change in water temperature occurs.

During April water temperatures hover in the high 40 degrees F, creating strong hatches of Blue Winged Olive (BWO) mayflies. On sunny days these mayfly species will trickle off and may not bring trout to the surface, but even if adult insects are not seen on the water’s surface, spring creek trout are most likely chowing mayfly nymphs or emergers subsurface. On cloudy days expect more intense hatches and look for rising trout in slower water, in runs, around weed humps, or along seams created by depth changes. 

Midges are active year-round on the spring creeks and make-up a massive chunk of a trout’s diet on Nelson’s, DePuy’s, or Armstrong’s spring creeks. Fishing midge patterns is best done subsurface in some of the deeper holes. If adult midges hatch, most spring creek trout rarely feed on hatching midges because adult midges rarely lay still on the water, rather they skitter in search of a mate. However, once an adult midge finds a mate, the “spent” or mated adult midge dies and its lifeless body is still on the water. 

Scuds, sowbugs, aquatic worms, and craneflies are also abundant in the Paradise Valley Spring Creeks. Strictly subsurface, these insects are active throughout April and readily available to hungry trout. Scuds and sowbugs are not exactly what an angler may think of when it comes to fly fishing a spring creek, but they are part of a trout’s diet. Often times thought of as the same insects, a scud resembles a freshwater shrimp and a sowbug looks like a “rolli-polli” bug. Even if they are different, a trout on the spring creeks in April may gobble up a size 18 or 20 scud or sowbug. 

Nelson’s, DePuy’s, and Armstrong’s fly box for April

BWO dry flies size 16 through 20

BWO emergers size 16 through 20

BWO nymphs size 16 through 20

Scuds in sizes 16 through 20

Sowbugs in sizes 16 through 20

Midges in sizes 16 through 22

Sculpin patterns in sizes 2 to 6

Streamers in olive or black in sizes 2 to 6