The Mothers Day caddis hatch on Arkansas River in Colorado is famous. Slowly the hatch creeps up steam in late April and early May dictated by the magical water temperature of 54 degrees Fahrenheit. A little extra snow melt cools the water and postpones the movement of cocooned caddis pupa squirming to the surface to shed their shucks and lifting airborne. But don’t worry; with 2 decades of water quality and structure improvement, the 102 miles of the Gold Medal freestone river from the Pueblo Reservoir to Leadville has a plethora of spring hatching bugs. Blue-wing-olives, caddis, golden stones, smaller dark stoneflies and midges now populate the waterway plus Colorado Parks and Wildlife recently introduced salmonflies which seem to like the Ark.
Dark (purple, brown or black) BWO nymphs size 20 to 26 and bright (chartreuse, orange or red) midge larva, also size 20-26, are always in the water column, moving up or down and deciding if the time is right to surface and hatch. The improvement of water quality on the river that endured a century and a half of mineral mining byproducts has changed the trout from smaller, short lived browns to a mixture of healthy rainbows and browns enjoying a longer life and growing to sixteen inches or more.
Until you see rising fish, Czech or high stick nymphing are the best techniques. Fishing with a long line and an indicator has limitations and works only in certain areas. Use a heavy attractor pattern like a golden stone, smaller dark stone or San Juan worm as the lead fly and a BWO nymph or midge larva pattern 12 to 18 inches lower. Methodically fish and try to reach all the parts of deep tail-outs below riffles, seams and deeper holding water. During the middle of a May day the trout will key into the specific hatch, either caddis, midges or BWOs. A dry fly as an indicator with the emerger of the same insect as the dropper is a good method. The sub-surface tends to be where the action occurs with so much competition with naturals on the surface. Dead drift with long leaders, good knots and fine (6x or 7x) tippets to weary trout.
The tailwater below Pueblo Reservoir is open to angling year round. The spring runoff captured from Arkansas River flows out of the dam at a fairly consistent temperature and generally close to gin clear. When high, discolored water surges through the freestone river section; this is the place to be. Public fishing is available for nearly all the water that meanders through the City of Pueblo. Anglers must pay a small fee in some areas. Colorado Parks and Wildlife have built structures for a decade, studied fish populations and created a first class fishery. The same techniques and fly patterns apply here as the mountainous head waters. The big difference is the city resides at a 5000 foot elevation and frequently has 50 degree air temperatures in January and February. Fly fishers feeling the effect of winter cabin fever, but hesitant to angle in cold weather will find they don’t have to wait for Mothers Day to catch big trout.