Very few statements can be made with 100% certainty in life or, more importantly, in fly fishing. But, this is one: Big Fish Eat Little Fish!
This basic statement of the prey-predator relationship is well known by saltwater fly anglers. However, for freshwater fly fishers, especially those who target trout, the fact that Big Trout Eat Little Fish appears to have retreated in memory. In this day and age of matching the hatch, precise imitations of mayflies, caddis flies and stoneflies and the use of smaller and smaller hooks, even down to size 32 for certain patterns, the casting of streamers and other baitfish imitations has lost popularity. Nevertheless, as long as there are fish, the larger ones will eat the smaller ones.
Fly tiers have used feathers and deer tails to fashion the deadly lures that we know as streamers. However, synthetic materials are now freely substituted for the natural materials or combined with natural materials to produce freshwater and saltwater streamers that are extremely effective for attracting game fish.
One terrific new synthetic material is known as Body-Fur. Body-Fur can make it very easy to tie quick and realistic imitations for both saltwater and freshwater patterns. The fibers of Body-Fur are attached to a core thread along with small bits of holographic flash. Once attached to the hook, the Body-Fur is wrapped in tight loops much like wrapping a hackle on a dry fly.
Materials:
Hook: Long shank [3x-6x]. This is dependent upon the size of the imitation you want to tie. Hooks that I have used and which have performed very well are the Daiichi X-Point X472 or Tiemco 911S for saltwater use, and Tiemco 5263 or 300 for freshwater patterns.
Thread: White, 3/0 to 6/0.
Tail: Grizzly Marabou. Other materials can be used depending on the pattern you are tying. I have used yellow marabou and yellow deer tail, tied in a split fashion, to duplicate the yellowish tail of certain sardines in the Caribbean.
By John Guldin
you can tie with Body-Fur can range from two-inch freshwater flies to six-inch saltwater varieties. Although Body-Fur is manufactured in many colors, white is the most versatile since it can be colored by Prismacolor® pens exactly as you wish. Joe Endy, a master fly-tier at the TCO Fly Shop in Reading, Pennsylvania, uses Body-Fur as a skilled artist uses a blank canvas. With a wide variety of colors, Joe has created incredibly realistic and effective flies that regularly catch brown, brook and rainbow trout, tarpon, snook, ladyfish, horse-eye jacks, salmon, steelhead, and jack crevalles.
The Muncher is a favorite of Ian James for carp, smallies, more. 
Thoughts of a Chicken Rancher. Doc tells it like it is.