The Scud Factor


Rainbow trout with Buzzcut Scud


 “The Scud Factor”

Dennis McKinney

            On a shallow shoreline on the far side of a mountain reservoir, overstuffed trout cruise by in the deep blue water beyond the weed line. Swimming slowly, the trout shop the edge of the weeds for edibles, inspecting all prospects carefully before committing, staying low, and never revealing their whereabouts with a telltale rise. Most are rainbows; a few are Snake River cutthroats – all are well fed.

I can not see them from where I wade near shore but I know they are there because occasionally one of them mistakes my fly for the real thing. Sometimes I land the trout and release it and sometimes the trout releases itself in the air over the weeds. Either way is all right with me. The biggest thrill is in the take, that single moment when science and skill come together and a homemade fly becomes trout food.

There was a time when thrills were rare for me on such a day. If trout were not rising, I was out of luck. I would cast for hours, switching flies until I had tried every one in the box. Biologists say that trout are opportunistic feeders – always ready to eat – but eat what?

I looked first to the nymphs of common aquatic insects: mayflies, midges, caddis, and damselflies. Through experimentation I discovered that all of these nymphs would catch trout occasionally, but none caught trout consistently. I had the same results experimenting with streamer flies that imitated crawfish, minnows and leeches. I discovered that if I trolled it behind a belly boat long enough, almost any fly eventually would catch a fish.  But eventually can be a long time.

The solution to catching selective well-fed trout in lakes and reservoirs remained a mystery until I began keeping the few trout that I caught and examining the contents of their stomachs. Occasionally I found the nymphs of mayflies, caddis, or midges. And sometimes I found crawfish, minnows, and even snails. But more so than anything else, nearly 100% of the time, I found scuds. The answer had been scurrying about in the weeds around my waders all along.

Scuds in folds of waders

Scuds in folds of waders

Scuds, commonly referred to as freshwater shrimp, are small crustaceans of the order Amphipoda. They inhabit the shallow substrate in lakes, ponds, and slow-moving streams throughout North America. Most are dark olive or gray in color, ranging in size from 5 to 20 millimeters. Although small, they are wildly prolific and can occur in staggering numbers. Plus, they are high in food value and easy forage for trout. In lakes with high concentrations of scuds, trout grow fast, often reaching five pounds in as few as three years.

In his Professional Fly Tying And Tackle Making Manual, first published in 1941, George Leonard Herter wrote, “These small shrimp are among the most active of water creatures. They wriggle, jump, swim, climb, and cavort with speed and grace. Where these scuds or shrimp are found they furnish very important food to such fish as trout, bass, crappies, bluegills and perch. Fish feeding on good supplies of scuds put on weight with unbelievable rapidity.”

Unfortunately, the scud patterns sold in most fly shops look more like sow bugs or saltwater shrimp than scuds. Scuds are long and slender and they swim with their bodies held straight. They propel themselves through the water with their rear legs, holding their front legs close to their body. Therefore, scud patterns should be tied on a straight hook instead of the common practice of tying them on a curved hook. Another common but unnecessary practice is tying a strip of plastic or latex over the back of the fly to resemble the hard shell of the scud’s exoskeleton. And by the way, scuds don’t have tails.

When it comes to flies, I have long held to the premise that a fly pattern should be both durable and easy to tie, and of course catch fish. I also believe that an impressionistic fly fools more fish than an exact duplicate. The scud fly described in the sidebar is about as simple as a fly pattern can be. Even novice fly tiers can master it after a few tries. It is nothing more than a rope of dubbing spun tightly around a weighted hook and trimmed into the shape of a scud. buzzcutscud

(See the Buzzcut Scud post for tying instructions.)    

Knowing when, where, and how to fish a scud fly becomes obvious when you learn their routine. As with all crustaceans, scuds are nocturnal. They are most active at night or other periods of low light, spending the brightest part of the day hunkered down in the shady interior of the substrate. Overcast days are ideal times for wading a shallow shoreline and fishing a scud fly over a weed bed. The darkness activates the scuds and sends them scurrying to the edge of the substrate in search of food, which soon attracts cruising trout. An even better scenario is an overcast day combined with a little chop on the water. Waves breaking on the surface diffuse the sunlight and help to darken the world below even more. Also, a broken surface allows fishermen to work closer to the fish without detection. On days when the conditions were right I have watched fat trout rooting around in the weeds for scuds like hogs.

The substrate is the scud’s habitat and they never venture far from it, preferring thick weeds or other dense types of aquatic vegetation. Thick weeds near a shallow shoreline are ideal, but any vegetation that grows near the surface can support a population of scuds. Oddly, they are seldom found deeper than five feet.  This is good news for fly fishermen, for they can wade and fish a shoreline or a weedy flat using a floating fly line.

Fishing a scud pattern properly boils down to making the fly act like the real thing. I had the opportunity to observe scuds in a large aquarium filled with aquatic vegetation. Usually they swam in a series of short, quick spurts and then rested momentarily. While resting they sank slowly. Other times, they swam straight for several feet before pausing. In bright light they hid in the vegetation, clinging to whatever they could find; including each other.

Techniques for fishing a scud pattern are basically simple but success increases dramatically with practice and focused determination. Begin by rigging a 5-weight or 6-weight fly rod with a floating line, a ten-foot leader, a two-foot tippet, and a weighted scud fly. The combination of the floating line and sinking fly will allow you to control the depth of the fly as you work it over the tops of the weeds. Cast the fly and wait for the fly to sink. After a little experimenting, you will know how long to let the fly sink and how fast to retrieve it so that it doesn’t hang up in the weeds. I have found that the best retrieve is a series of short, fast twitches followed by a long pause to let the fly sink. Be aware that hits are likely to come while the fly is sinking. For this reason, it is important to keep all slack out of the line and pay close attention while the fly is sinking. With too much slack in the line, a trout can inhale the fly and spit it out before you know it.

Experiment with the retrieve, letting the fish tell you what’s right for them. Sometimes slow, steady, hand-twist retrieves are better than the stop and go twitching. At other times, the trout might want a fast retrieve without any pauses. When the wind blows hard, making it impossible to stay in touch with a sinking fly, the only option is a steady retrieve to keep slack out of the line. Fortunately, trout seem to hit the fly harder when the wind blows.

The great still-water insect hatches of summer come and go, bringing with them short-lived rounds of easy fishing. A burst of caddis or mayflies on the surface has the power to turn the wiliest of trout into imbeciles. Scuds on the other hand may never send trout into surface-feeding frenzies, but never will they sprout wings and fly away. The scud is a fly for all seasons – the go-to fly in tough situations.





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