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Entomology

Scuds

Bubba Gump might call them shrimp. Trout simply know them as food.

Eons ago, my good friend John Marcacci and I drove to the Green River for a day’s fishing. It was back in the time when it didn’t seem remarkable that three days of driving would net only ten hours of fishing. This was before they invented designated drivers and getting there was half the fun.

We were having so much fun getting there that, at dark-thirty on a dirt road in the middle of the Utah desert, it didn’t seem relevant that we were passing official looking US Government signs suggesting we immediately stop and turn around. It didn’t even seem too relevant that a very sturdy gate blocked the road. We simply four wheeled onto some railroad tracks and kept on truckin. At that point the only thing that mattered was that the ice chest wasn’t quite empty and we were heading south towards great fishing. We thought we were going east.

We must have pulled over to take a nap because the next thing I remember I was waking up feeling ill. I blamed it on the (gorgeous) black widow spider that dropped out of my sleeping bag. John was actively getting sick but since he didn’t sleep with a spider he could only blame the cheap beer.

The truck was sandwiched between heaps of what looked like rusted missiles with jagged holes blasted out of their sides. Between retches, John suggested they were drones used for navy target practice. Pitched in the sand, skeletal railroad tank cars with ANTHRAX stenciled on their flanks hulked silently as spindrifts of snow and alkaline dust swirled through their rotting carcasses. We were in a military junk yard.

We built a small cooking fire from a pile of eight foot railroad ties and brewed some much needed coffee. While sipping the joe we tied flies by the warmth of the fire some forty feet away. We had been told that the only thing Green River trout ate were scuds. Neither of us had ever seen a scud before, but armed with a Herters catalog we copied the pattern from it’s dog eared pages.

Just like many modern scud patterns, we bent the hooks, dubbed scraggly bodies, added a few wraps of mallard flank, pulled a strip of plastic over the backs and ribbed them with light wire. After tying a few that looked like the picture our hands were trembling so badly (was it the cold, the beer or the anthrax?) that we couldn’t grip the plastic so we omitted that step. Pretty soon we decided since we didn’t need to tie down the plastic, we might as well save time and not tie in the wire either.

We finally got to the river and could only stare, goggle eyed, at all the really cool trout, finning in the very cool water just below our extremely cold feet. We kicked over a few rocks and clouds of scuds billowed into the current where the trout eagerly darted to and fro feasting on the bounty. It was just like the wild rumors we had heard in California, except that the fish didn’t want our flies.

After a juniper reached out and stole his fly on a backcast John tied on another scud and suddenly started catching fish. I watched closely and made sure he wasn’t dipping his flies in Dr. Juice or tipping his scuds with caddis larvae. He was being uncharacteristically kosher. I asked what he was doing different and he shrugged his shoulders, smiled smugly and said wisely, "I dunno".

Just to be doubly sure he wasn’t smearing just a little Powerbait on the fly I offered to help him release his next fish. As we were unhooking the trout we both realized that he had tied on one of the flies without plastic or wire. It was just greenish dubbing with a wrap of duck flank. . .very similar to a Bird’s nest, except that we didn’t know what those were back then.

I scooped up some of the living scuds and watched as they scurried about in the diminishing puddle of water in my hand. They nuzzled into the darkness between my fingers and I learned two important lessons about scuds. First of all, swimming scuds, the kind fish are likely to see, are as straight as a needle and only curl up into the typical scud fly profile when they are crawling around on something. The second lesson learned was that I liked these little guys.

Typical greenish scud clambering over a rock in a Truckee creek.

Since then I’ve spent an embarrassing number of hours underwater watching scuds and watching fishermen try to trick fish into eating scuds. For those moments I can’t be on the water, we have an aquarium in our kitchen that has become home to countless generations of scuds.

Like crayfish, shrimp, and sowbugs, scuds are Crustaceans. They belong to the order Amphipoda which contains three families. Gammarus and Hyalella are the families of greatest importance to flyfishers. Like insects, scuds periodically shed their exoskeleton but unlike insects, scuds don’t have nymph or pupal stages. Baby scuds look like their adult counterpart, only cuter. Scuds require a relatively large amount calcium to support their molts. Scuds are found almost exclusively in alkaline waters and where ever they are found, trout actively seek out these nutrient rich packets of energy. In scud-rich waters such as Eagle Lake, I’ve seen trout bellies distended by hundreds of scuds. To offset such intense predation, scuds are remarkably prolific.

Scuds populations have been measured as dense as 10,000 creatures per cubic meter of water. A single pair can spawn half a dozen times in a year and produce 20,000 young. The single largest threat to scud populations is the rapid drawdown of tailwaters below dams. On one scud laden Truckee River tributary, it is common to find windrows of dead and dying scuds when the river flow is abruptly cut. These normally light olive scuds turn bright orange when they die and trout in this creek are quite color selective when flow patterns change.

This scud is nearly dead, stranded in a puddle created by an abrupt dam shut down. When the dam reopens, the trout in this Truckee River tributary feast on the dead scuds that get swept downstream. At this time the fish won't eat a green scud pattern.

Scuds are generally reported to be herbivores and scavengers. Our pets are vicious predators. They will dart from cover to attack tubefix worms and will even tackle small backswimmers who in themselves are pretty lethal creatures. Scuds can easily overpower Siphlonurus mayfly nymphs seven fold their weight and we have witnessed scuds, sometimes in groups, attacking and killing tadpoles.

Though scuds live in the shallowest margins of lakes and streams, they intensely dislike light. They typically hide in deep cover while the sun is shining but quickly come out to forage when the skies dim. I’ve watched fish boiling through masses of scuds as they rose out of Elodea mats when afternoon cumulous clouds melted shadows across the lake. As soon as the sun broke through the clouds, the scuds would vanish and the melee would cease. Under overcast skies, scud patterns will very often outfish "normal" nymph and pupa patterns.

Scuds have seven pair of legs, the first two are used for grasping and manipulation while the other five pair propel the bug with synchronous ripples. When swimming they stretch out completely straight (curved scud patterns not only look wrong when stripped through the water, they have poor hooking ability) and the scud bends into its characteristic curled position when it scuttles about along the streambed or among the vegetation.

When scuds swim they become a blur of buzzing legs, whisking antennae and fluttering gills; they travel upside down as often as not. There is no such thing as a good scud imitation. Don’t even try to fool an educated fish into believing your hunk of Visqueen and feathers is the real thing. The occasional trout might eat it, but only because he’s greedy.

Instead of trying to make a scud imitation, make a scud impression. Give the trout something that moves and twitches and doesn’t have an up or a down or a sideways. Give them something simple like a Bird’s nest. Something that can be tied with frozen fingers on a military waste site in the morning after a forgotten night.