Scuds

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This is me releasing my new scuds

This is a partial re-post of an article at http://www.flyline.com/entomology/scuds/


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.


I have not ordered from this outfit, but Jon Parr has and said it was good
http://www.nilesbio.com/prod295.html