SCUDS - An excerpt from the book 40 Great American Trout Flies by Craig Schuhmann

Posted by Nick Amato on



  • Originator: Unknown
  • Type: Imitative
  • Imitates: Scuds and sow bugs
  • Common Sizes: 12-16
  • Common Variations: none 
  • Hook: Scud hook, size 10-14
  • Thread: Black 
  • Tail: Hen saddle
  • Body: Hare's ear
  • Scud Back: Clear or colored scud back
  • Antennae: Hen saddle Rib: Wire, small
  • Bead Head: Optional


Scuds, along with sow bugs Sand crayfish are freshwater crustaceans similar to their marine cousins, but exist in less­-dense populations. Freshwater crustaceans are found mostly in nutrient-rich waters such as lakes, spring creeks and tailwater rivers. These types of waters provide stable conditions of water temperature and flows required by both insect and the aquatic grasses on which they live. Sandy- or rocky-bottomed rivers which often lack the required vegetation will have few to no scud populations. All crustaceans are rich nutritionally, as well as being very vulnerable to trout. Trout that feed on scuds and other crustaceans tend to grow big and have richer-colored red meat.

The best way to detect scud or sowbug populations is to sample the grasses in the river or lake. One can use a fine-mesh net or their hands to run through the grass and collect a sample. Scud are a year-round food source on most rivers and lakes, but their populations will increase as weed growth increases. In spring you will see fewer scud populations than in summer when sunlight is conducive to greater weed growth. Rivers known for their scud populations include the Missouri and Bighorn in Montana, and the Henry's Fork in Idaho. 

Scuds come in a range of colors, but the most common is gray, which has a translucent appearance, and olive, which mimics the color of weed growth. When scuds die they turn light pink or pale orange. This gives justification for patterns tied in bright fluorescent colors. The most common size range for imitating scuds is between 14 and 16, but they can run bigger or smaller depending on variables in your particular river or lake.

There are many scud patterns available, but since imitating them is simple, most look very similar. Color may be the biggest determining factor on any particular river or lake. Scuds have a shrimp-like appearance with segmented bodies, long antennae, fourteen pairs of legs, and a hard shell-back (caprice). They are agile swimmers, darting among the grasses in search of food or a mate. Most patterns are tied on a curved hook to imitate the curled-up appearance when they are picked up by anglers or clinging to grasses. Mike Lawson in his book Spring Creeks suggests trying patterns tied on straight hooks because, "Scuds straighten their bodies when they swim. Scuds move quite rapidly, but many anglers move the fly too fast when fishing scud patterns." Trout do take advantage of drifting scuds that have broken free in the current, but they are just as likely to be found rooting in the grasses. This is an unusual feeding behavior not normally witnessed by anglers. I have only seen it on a few spring creeks such as Rocky Ford in Washington State. When trout are rooting you will only see their tail and body angled up, waving and balancing itself, with their head buried in the weeds.

Fishing with scuds is as easy as using the dead-drift nymphing technique, either with or without an indicator. One only needs to learn where in a river or lake scuds are located. I never drift my presentations directly in the weeds, which would only result in hang-ups. Rather, I look for low-growing weeds and drift my imitation at weed level. Better yet, I will look for channels in the weeds and get my imitation as deep as possible. If your imitation doesn't have a bead head, or some other weight, use split shot on your leader. Identifying the channels in weed beds can be tricky. It often takes good observation skills and positioning on the angler's part to be able to access the channels. A pair of polarized glasses that cut through the surface glare will help with this process.

The importance of scuds should not be underestimated on rivers that contain them. I always carry a few patterns in a range of colors for those unknown times when they could be the important fly.



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