06-12-2010, 12:32 PM
Depending on the available food they can imitate a lot of things-- in freshwater they can imitate frogs, big bugs, or baitfish.
In salt water they most often imitate baitfish of course, but flies like gurglers can also imitate shrimp and marine worms that swarm on the surface usually at night.
Besides being so exciting to fish, they can also be really effective.
Gamefish, including bass in freshwater and all kinds of stuff in salt water often trap baitfish on the surface by attacking them from below. A popper thrown into a school of feeding fish can be deadly.
But even a when there's no surface activity going on, a slowly worked popper may look like very vulnerable, easy meal-- a bug trapped in a the surface film, a frog away from cover like lily pads, an injured baitfish flipping around, or they may just annoy the heck out of fish.
Since fish have lateral lines that sense vibrations, I also think that poppers are so effective because of the sound waves they send out that allow fish to home in on them.
As an example, a couple years ago, I was fishing a "mullet mud" in Florida (a dense school of mullet stirring up mud on the bottom as they feed) in about 3 feet of water. We were catching specs and a few ladyfish. Even though we were releasing everything and using barbless flies, one of the ladyfish we caught didn't recover and was just laying on its side, flipping around on the surface. We forgot about it and keep casting and fishing. About 20 mins later a huge compression wave comes zeroing in across the flat (ignoring our flies) and the water exploded like someone dropped a Suburban in the water. After the waves subsided, the ladyfish was gone.... thanks to a 120lb or so tarpon.