Amphipoda: Scuds

photo: Alex Cerveniak

Size: I’ve found them anywhere from 4mm to 15mm, though I have read that they can grow up to 25mm.

Color:

• Since their bodies are semi-transparent, their digestive tract can be seen through their shell.  Therefore, coloration usually matches what they’re eating or their surroundings.
• Common colorations are cream, olive, tan, gray, blue-green, brown, and reddish-brown.
• While females are pregnant, their orange egg sac can be seen

Habitat:

• Scuds are highly abundant in both streams and lake/pond ecosystems.
• They feed off of dead plant and animal material, so they’re more abundant in weedy areas, or areas with a lot of leaf litter.
• Can be found in areas with slow to fast current, but prefer areas with slow to medium current as this is where the majority of their food is found.

Behavior:

• Scuds, sometimes called backswimmers, swim by contracting their abdomen (see video tab above).  They move in short bursts, with a momentary pause between each burst where they slowly sink.
• Their appendages are constantly in motion, which should be kept in mind when choosing fly tying materials to imitate them
• Highly effective to use while fishing spring creeks
• In large tailwaters, scuds will often become stranded in small puddles when water levels are dropped, where they often die.  When water levels are bumped back up, these dead scuds are washed downstream.  During these situations, dead drift a white or cream scud imitation.

Imitations:

Golden Scud- Click Photo for Recipe

Olive Scud- Click Photo for Recipe

Troutnut.com’s Scud Page
General info on scuds, plus excellent reference photographs

Fly Fishing Republic’s Scud Page
Scud info, including life cycle and angling techniques

Westfly’s Scud Page
Great info on scuds, as well as some nice photos