The easiest way to catch a big fish on a fly is on a streamer - a wet fly that imitates a small baitfish that larger fish feed on. There are many streamer baitfish imitations that will catch fish in lakes, streams, ponds and in saltwater.
If you can cast 20 feet, you can catch fish in streams and rivers on a streamer. You can even strip line off the reel and into the water and let the fly drift in the current and catch fish. The line swims the fly, making it look like a swimming baitfish. Cast a streamer such as a Woolly Bugger into moving water, and expect a strike from a hungry fish.
To improve the action, attach a split-shot to the leader just ahead of the fly and give the fly rod tip a bounce now and then as the streamer drifts downstream. The bounce of the tip causes the fly to jig up and down like a wounded minnow, and all gamefish are hunters for wounded baitfish.
Big saltwater or freshwater streamers require bigger fly rods to cast - 7-weight, 8-weight or larger rods. The larger the fly, the larger the fish you'll catch and the larger the fly rod you'll need to cast and fight the fish (small flies can also catch large fish).
BAIT FISH STREAMERS
When fly fishing streamers, first determine which baitfish the larger fish feed on where you fish. For example, if you're fly fishing for bass in a stream and the bass there feed mostly on crayfish, you'll need a fly that looks like a crayfish. But if silver-colored minnows are their main food, then you'll want to use a silver minnow streamer.
While the fly line will swim the fly in moving water, it will not swim it in the still waters of ponds and lakes. You have to swim the fly by casting and retrieving the fly. The farther you can cast, the longer your retrieve of the fly and the more fish you'll catch.
Different lines retrieve the fly at different levels in the water. For instance a floating line will fish and retrieve the fly near the surface. But if the fish are deep, you need to get the fly deep to catch them. And you'll need a sinking line to get the fly down to the fish.
FLY LINE WEIGHT
Sinking lines are heavier than water. The heavier the line (Type 1 or I sinks slowest and Type 5 or V sinks fastest), the faster it sinks. In deep water or fast-moving water you need a Type V line to reach bottom with the streamer. In slow-moving shallow water you need a floating line or a Type I. On lakes an intermediate line or a Uniform Sinking line from Scientific Anglers are great for fly fishing streamers below the surface.
Fly fishing the streamer in ponds or lakes is simple - cast and retrieve it with a slow hand-twist retrieve or simply let it swing and follow behind the boat or float-tube as you move. The fish will do the rest.
When fly fishing the streamer in streams, simply cast the streamer across the current and let the flow take it downstream. Most of your strikes will happen at the bottom of the swing. Cast the streamer toward the bank when fishing from a boat and retrieve it fast. Bass and trout will leap on it!
Streamers can serve you very well on the water when you’re aiming to catch larger fish. However, don’t forget about using dry flies and nymphs to catch a variety of great fish, as well. See a chart that lists the classic patterns for dry flies and nymphs.