This is a technique I was taught for catchings Reds and Trouts alike!
Small plastic beads are commonly used with a popping cork rig. They are attached to a short, stiff wire that passes through the cork, above and below the cork. The beads add a "clacking" that imitates the sound shrimp make when snapping their backs to quickly flee a predator.
EQUIPMENT AND TECHNIQUE
A sturdy rod with enough backbone to control casting the rig, but not so heavy that casting and tugging repeatedly wears you out, makes a good combination. A light- or medium-weight 7-foot graphite rod is sufficient. Keep the rod tip up with the line out of the water, so as not to rip it across the surface when giving the cork a pop. Also, keeping excess slack out of the line allows you to quickly set the hook when the cork goes under.
More often than not when fishing in salt water, there is a wind blowing and you will have a "belly" in your line. Just keep taking in slack and after you give the rod a few jerks to pop the cork, you should get a feel forhow much "belly" you can handle and what it takes to set the hook when needed.
In deeper or choppy water, you can be more aggressive with the tug in strength and frequency, giving it a sharp pull every few seconds. In very shallow and calm water, a more conservative approach works better. Give the smaller-sized cork a lighter tug and less often. A light pop every 30 seconds or so may be all that's needed in order to not spook the fish.
Watch that the cork floats freely and upright. A cork leaning to one side is either tangled up in the line or hung up on the bottom. Give it a tug to free it.
BEST BAITS
By far, shrimp are the most common bait used on a popping cork. There are not many situations where a shrimp won't attract a speckled trout or a redfish. In fact, if you aren't getting bites with a live shrimp, then it may be time to try another spot or even another day. If the only bait you use is shrimp, you are likely to catch plenty of fish.
On days where the water is stained or your live shrimp aren't producing bites, try pinching the heads to release more scent into the water. This helps the trout or reds to home in on your offering.
There can be a downside to shrimp, however. If the area you are fishing is loaded with pinfish or other nuisance species, then they can get to your shrimp before the trout and reds do. Soft, artificial shrimp imitations, such as Berkley Gulp!, can work just as well. They hold up better to the pecking of the smaller baitfish and allow the bait to remain in the water long enough for a bigger fish to take hold.
Small pinfish and scaled sardines or "whitebait" also work well under a cork. Hook minnows behind the pectoral fin so they stay low in the water.
A jig or a spoon can even be used under a sliding cork rig. Once a trout or red is attracted to the popping sound, it can be fooled into attacking what appears to be a minnow escaping into the grass. A falling lure may draw an impulse strike from a fish that isn't necessarily feeding.
Keeping an attentive eye on the cork is still required at all times. The cork is your indicator of when you have a bite. You almost never feel the fish until you pull up hard setting the hook.
