July Fishing on the Ruby River

July weather, stream flows, and summary

The challenge of high stream flows exists in May and June on the Ruby River, but July sees this small southwestern Montana river come into prime form. If only access were easier, then it would top nearly every anglers list of favorites. With two distinct sections, the Ruby River has a variety of fishing options, but access is difficult in both sections. 

On the Ruby River in Beaverhead-Deerlodge National Forest the river has ample public access. Here small, eager fish dominate. From the national forest boundary to Ruby Reservoir the river flows through private property and access is limited. Below Ruby Reservoir brown trout become the focus of anglers…and some of the trout are large—fish over 20-inches are common on the Ruby River in July.

During July stream flows on the Ruby River remain relatively consistent. Because the river is used heavily for irrigating rancher’s hayfields, the outflows from Ruby Reservoir rarely drop below 250 cubic feet per second (cfs) and rarely rise above 300 cfs. Granted these levels are still high for walking-and-wading anglers, but because the Ruby River has several ditches that divert water, stream flows in July are often very conducive to walk-and-wade angling. Float fishing is nearly impossible on the river as numerous small diversion dams make floating very difficult and dangerous. 

However, for anglers able to gain access or commit to some very serious wading—oftentimes chest or neck deep—July on the Ruby River can be exceptional. The Ruby River twists and turns for miles through thick willow and tree-lined banks. With deep holes and undercut banks, the Ruby River downstream of Ruby Dam is ideal brown trout water. 

Similar to the fishing action on the Ruby River in July, the weather in July is consistent. Early July sees average daily high air temperatures in the high 70 degrees F while by month’s end the average daily high temperatures rise to almost 85 degrees F. Measurable precipitation is only likely to fall on less than five days throughout the month. Simply put, July is hot and dry on the Ruby River. 

July fishing: what to expect

July on the Ruby River is prime time for both sections of the river. Above Ruby Reservoir, stream flows are low and clear, making walk-and-wade fishing readily available. The most accessible water lies in the uppermost reaches in Beaverhead-Deerlodge National Forest. In this section anglers can find fish averaging 10” – 12” inches and eager to eat a well presented dry fly. 

Once the river leaves Beaverhead-Deerlodge National Forest it flows through large tracts of private land and access is difficult. Below Ruby Dam, the river travels for a few short miles through a scenic arid canyon before abruptly transitioning into a meandering open agricultural valley. Two public access points exist in the upper three miles and an additional two in the next six miles. However, private property surrounds each of the small plots of public access limiting anglers' ability to cover substantial tracts of water. 

Hatches of Pale Morning Dun (PMDs) mayflies and caddis are often strong in early July. By month’s end, tricos and terrestrials dominate the dry fly charts. But because the Ruby River is home to Yellow Sally stoneflies, midges, mayfly, and caddis species, these aquatic insects are active subsurface in the height of summer. Anglers choosing to fish a two-fly weighted nymph rig will find some success. Choose any combination of the following: stonefly nymphs in sizes 8 through 12, mayfly nymphs in sizes 14 through 20, midge larvae in sizes 18 to 22, or caddis pupae in sizes 14 through 18. 

If water temperatures stay in the low 60 degrees F look for hatches of PMDs, caddis, spruce moths, and tricos. A few late hatching stoneflies may occur, but they will be seen early in the morning. Terrestrials may be abundant as well. 

For PMDs choose mayfly dries or emergers in sizes 12 through 16. For PMD nymphs choose beadhead Pheasant Tails in size 12 through 16. For caddis, choose dry flies in sizes 12 through 18 and nymphs in sizes 12 through 18 as well. Most caddis adults will be tan or olive in color. 

Streamer anglers will find aggressive trout in July, particularly in the lowlight conditions of early morning or late evening. Choose olive, black, or black/brown sparsely dressed patterns in sizes 4 through 8. A black or olive conehead Sculpzilla is a guide-favorite for mid/late June. 

Where to find July trout on the Ruby River

Caddis, small stonefly, and mayfly nymphs along with midge larvae are active on the Ruby River in July. Terrestrials begin to show up in good numbers by the end of the month. Because hatches are strong and terrestrials are abundant, trout on the Ruby River can be found in a variety of places. 

For both sections of the Ruby River—above and below Ruby Reservoir—look for trout throughout all possible feeding lies—near bankside structure, seam lines between slow and fast water, shallow flats, riffle corners, and the heads of deep pools. 

The Ruby River has an abundance of aquatic insect life. Because food is prevalent in many habitats, trout inhabit many places, but they are most often found along the bank, in riffles, shelfs, the heads of runs, and the tail outs of runs. These habitats all offer the primary needs for trout: available food source, cover from predators, cover from strong currents, and flowing water for oxygen. 

In July on the Ruby River, anglers typically rejoice because the trout tend to be hungry and happy and in the right spots.

Important July hatches

The possibility of great days of dry fly fishing on the Ruby River are greater in early July than later in the month. Caddis and Pale Morning Dun (PMDs) mayflies make up the bulk of July hatches on the Ruby River, with Yellow Sally stoneflies being the largest aquatic-based insect to hatch. 

A variety of caddis species ranging in size from 10 to 20 live in the Ruby River and hatch throughout the month, occurring at various times throughout the day. 

PMD hatches typically begin mid-morning and last for several hours. Insects range in sizes from 12 to 18, with most being size 16. As a mayfly, it is important to understand trout may feed on emerging PMDs and not exclusively on fully hatched adults. 

Terrestrials—insects that live the entirety of their life on land—provide a large portion of a Ruby River trout’s diet in late July. Grasshoppers, crickets, ants, beetles, spiders, and any other land-dwelling insect that may inadvertently find its way onto the surface will be targets of trout as well. In the section of river flowing through Beaverhead-Deerlodge National Forest, spruce moths are abundant. 

Trico mayflies hatch in July on the Ruby River as well. These small mayflies—sizes 18 through 22—hatch in the early morning hours. Trout rarely feed on trico nymphs but will often rise to adults floating on the surface or “spent” adults—insects that have mated and are now dead. 

Ruby River fly box for July

Caddis pupae size 12 to 16

Caddis CDC emergers size 12 to 16

Caddis dry flies with dark grey, black or brown bodies in size 12 to 16

PMD dry flies size 14 to 18

PMD emergers size 14 to 18

PMD nymphs size 14 to 18

Spruce moths in size 16

Stonefly nymphs in brown and black in sizes 8 through 12

Sculpin patterns in sizes 2 to 6

Streamers in olive, black or brown in sizes 2 to 6

Grasshoppers in sizes 6 to 10.

Trico mayfly adults and spinners in sizes 18 through 22