"Scuds inhabit lakes, rivers of all sizes, springs and streams. One study found a population density of 10,000 per square yard (meter). You can see why they are an important food source for trout.
SCUD FLY PATTERNS. (also a great freshwater shrimp or louse imitation) Hook size 14 16 18 - $US each
There are many different ways to fish a shrimp scud fly but you should always remember the life style of the lowly shrimp and try to match it. The fly should be fished close to weed beds close to the water margins. Do not waste your time casting out into deep water. In the winter with a current or after a summer rainstorm shrimps will often get dislodged from under rocks and logs. They are at the mercy of the strong water flow, ending up on the bottom. When suspended in the water they move at the same speed of the water. It is vital that you fish your fly dead drift so that it moves at the same speed as well. The shrimps do not try to swim against the tide and therefore you should not try to imitate it swimming otherwise you will definitely come up a blank days fishing. When they land back on the bottom they are very open to attack from hungry trout until they can find new safe cover. In these conditions it is best to have a heavy shrimp point fly and two droppers floating at different levels in the water column.
Fishing with a single fly gives you more freedom. It is ideal in shallow water. The fly can be allowed to drift longer and therefore fool more wary fish that your fly is the real thing. Cast upstream and allow the fly line to move with the current of the water. Retrieve the line at the same speed that the water is moving at. You are therefore in contact with the fly so you can strike as soon as a fish takes your fly. In stillwater or very slow moving water conditions the situation is reversed. You have to suggest movement to attract the attention of patrolling trout. Try to imitate how a shrimp moves. Being tiny it moves in very small irregular erratic jumping spurts. Use small sharp jerks or an erratic figure of eight retrieve. Try varying the sped and length of the strokes to maintain interest. No shrimp moves with consistent regular systematic movements.
Try to find out the color and size of the local shrimp population by spooning a caught fish or turn over rocks near the shore. Males, during the breeding cycle, change color so make sure you try to match it otherwise you will lose out. Shrimps do like water with high oxygen content so look out for a water inlet or other fast flowing water source coming into an area of stillwater. Cover this with a shrimp pattern as they will probably be there along with the hungry fish.
I was stillwater fishing, sitting quietly in my boat. Trout were cruising right up to and under my boat. I could see their white mouths opening as they fed but could not see what they were taking. About 10 feet away I observed one trout tip up and root his nose around the lake bottom. He created a small cloud of silt and debris. This commotion attracted other trout. I guessed they were feeding on scuds as there was no observable hatch taking place. They were feeding on some small food items. I allowed the pattern to sink. After 10 seconds I began a slow hand twist retrieve with a couple of quick 3 to 4 inch strips. My line tightened. I lifted my rod. The water erupted. I slipped my landing net beneath a beautiful 4 lb rainbow. I caught 7 good sized trout using your Scuds. Thanks. George Ryan, Seattle