Pogies (or Menhaden) are a type of shad that spend their lives between brackish water river estuaries and nearshore bays. They are grey-silver in color with a green tinted back and yellow tinted fins. They have a black spot behind the gill cover, and may or may not have a row of smaller spots along the lateral line (depending upon the species). They can grow five inches in their first year, and can grow up to twelve inches during their five to six year lifespan.
Pogies are not good table fare, but make excellent bait. They are very oily, so active feeding of prey, such as redfish or speckled trout, can often be identified by a slick on the water (especially if the slick is below a bunch of gulls picking at the water). It is difficult to keep pogies alive for very long in a livewell -- it is best to use a round cornered livewell with lots of fresh circulating sea water. This keeps the pogies swimming and not sloshing around too much, like you would see in a square tank.
They are easy enough to catch with a cast net, so don't bother buying them at a bait shop. They wont survive long in captivity anyways (click here for instructions on throwing a cast net). Look for shimmering at the water surface to locate schools of pogies. Trout or redfish are probably not far behind.
When using live pogies for bait, I find that it is best to use a 4/0 circular hook, and hook the pogies through both lips if you want the bait to swim down, such as when fishing under a bobber at the surface, or through the tail if you want the fish to swim up, such as when fishing on the bottom. Dead pogies can be cut or ground up and used for chum; their oily flesh makes a great attractant. Hook young pogies about two feet below a popping cork, with a split shot in between. Cast out and pop the cork periodically. This is a great way to catch trout and redfish. The same technique can be used with live finger-mullet, croakers, or shrimp.
Sometimes in fall, you will see millions of large pogies in the water, especially at the mouths of rivers. There is no use in using live pogies for bait at this time, because there is nothing that distinguishes your bait from the other million shad in the water. Use a freshly killed shad at this time, and fish off of the bottom. The big redfish that follow the schools around are lazy, they wait for dead or dying shad to sink down to them. Use a 1oz egg sinker above a swivel and 2 foot leader with a circular hook. Hook the dead shad through the eye sockets, then cast out and let the bait drift along the bottom with the current on an outgoing tide. I have caught huge redfish this way (see red bull), and nice black-tip sharks. You will also catch some large nasty catfish, but that is a hazard of this game.