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Scientific Names: genera Gammarus and Hyalella

Common Names: Scud


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SIZE: 3-25 mm (1/8 to 1 in)

COLOR: Olive, tan, gray; may have orange spot

OTHER CHARACTERISTICS: Shell-like, curved back; many legs on underside.


About Scuds

Scuds are shrimp-like, freshwater crustaceans. They can occur in huge numbers in lakes and in slackwater sections of rivers. When present, they offer trout a delicious morsel that's hard to resist.

Scuds favor weedy areas, but can be found other places as well. Because they are sensitive to light, the best times to fish an imitation are on overcast days and near dawn and dusk. A healthy scud population results in large trout with deep bellies.

Scuds swim in spurts. Each spurt is 6-12 inches, and there is a pause between each. So on a lake or slackwater, use a sinking or intermediate line and retrieve the fly with short strips, pausing between each strip.

On rivers, scuds may be found either drifting or swimming. Drifting a pattern just over the top of a weed bed can be very productive. A swimming scud will straighten its body, whereas a drifting scud will curve itself; choose a pattern that matches your presentation.

Past conventional wisdom was that scud eggs are orange and are carried by the females under their belly; and that pregant scuds were favored by trout. Confimmation seemed to come from success: an orange-tinted pattern can be deadly. However, Jeff Morgan, author of many fly tying and entomology articles for Westfly, has done some research on the subject. The research says that the orange tint is a parasite and that trout clearly zero-in on it. For whatever reason, it's clear that orange-tinted scuds patterns are very effective.

Gammarus scuds are typically 10-25 mm long, while the Hyalella scuds are a tiny 3-5 mm. Don't automatically assume trout only want the big ones! There may be a preference.

Articles About Scuds

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Scud Tactics Trout scarf down scuds in lakes and slow-moving, weedy rivers. Learn the tactics for fishing scud patterns. Mike Schoby


Scuds. (photo © 2006 Arlen Thomason. Used by permission.)

Matching Scuds

Only standard fly patterns are shown. Click here for all matching flies in the database.








6-16/Olive, tan, olive-pink, olive-orange

Indicator, Tight line, Shallow nymph, Count-down-and-retrieve, Slow retrieve, Wind drift

Slow runs over weeds, lakes

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