Palmer, my father, eased the throttle back and spun the helm to the southwest, positioning the venerable 18-foot Seacraft into position for the first drift across the Islamorada Hump.

The sea surface, becoming more of a mirror as the late afternoon sun slid lower, was barely wrinkled with light ripples, a stark contrast to the wild seas that can develop over the seamount projecting up into the flow of the Gulf Stream. The characteristic Back Rip, often a line of foaming stationary breakers over the downcurrent crest of the Hump, was only a slender, dark zone of 6- to 8-inch wavelets, visible to the northeast as we settled in to drift.

I scooped a net full of pilchards from the livewell and hooked four to a 50-pound teaser line, then sent them out behind the boat. Palmer kept the bow southwest into the current, idling gently in forward gear as the four terrified baits darted around 30 feet back from the transom. I tossed a second scoop of pilchards back on top of them. The free swimmers clustered around the teaser--a distinct ball of bait creating an irresistible silhouette for bruiser blackfin tuna cruising 20 to 80 feet below.

Three more baits on 20-pound spinners, armed with the same hooks as the teaser and no leader, one freelined back yellowtail snapper-style by my wife, Wendy, and the other two held at the boat ready for casting to the teaser, and we were set.

Suddenly, an explosion of foam and pilchards jolted us like an electric shock. A pack of blackfins rocketed vertically through our living chumball, crashing through the calm surface to create a 5-foot-high spray of pilchards and white flecks of seawater. Palmer, and our friend Liz McCutcheon, flipped their baits into the melee and loose coils of monofilament immediately began ripping loudly off the spools. Palmer closed his bail after a fast count, wound like a madman, and lifted his rodtip sharply when he felt resistance. The rod doubled and the drag screamed. Liz, on her first tuna outing, was in a state of shocked silence as line piled off her spool. I backhanded the bail closed and everything else took care of itself, the blackfin coming to the end of the slack at 60 mph and impaling itself, nearly snatching the rod overboard as Liz let out a squeal of excitement.

Twenty minutes later, Palmer's fish had gone through the leader only 25 feet away from the gaff, Wendy had pulled the hook on a third fish, and only Liz's fish remained, flashing silver in the indigo depths. Beads of sweat covered her forehead and upper lip as she did a good job, with no shortage of advice from the peanut gallery, lifting the rod slowly and firmly in short, even strokes, dropping and reeling, slowly gaining on the dogged but tiring fish.

Mindful of Palmer's fish now swimming away, I leaned over the gunnel with the gaff and stuck Liz's fish on the inside of one of its circles five feet down, and snatched it aboard. It went 22 pounds, a great first tuna on 20-pound spin.

We finished out the afternoon with three more drifts. The fish continued to respond well to our technique and we knocked off after Palmer came through with a fat 28-pounder to wrap up the day.

Seamounts such as the Islamorada Hump are quite simply mountains rising from the sea floor. When located in current like the Gulf Stream they present an obstruction to the prevailing water flow, causing it to "squeeze" around and over it. The vertical component of this squeezing action sends water from deeper layers boiling to the surface, along with a menagerie of organisms not normally concentrated near the surface--squid, preyed on directly by gamefish, as well as zooplankton, fed upon by schools of flying fish which in turn become prey for surface predators like dolphin, blackfin tuna, and an occasional wahoo and billfish.

Most anglers know that structure and associated turbulence create productive feeding areas for target species, but many don't extend the analogy to the quest for live bait, the biggest single denominator for a successful Hump trip.

Off Islamorada the primary bait species are pilchards, cigar minnows, and ballyhoo. Mackerel scad (dubbed "speedos" by locals) are sometimes cast netted, but are more often captured by circular hoop nets suspended under chumbags and lifted quickly, or by hair hooks, the main method for catching blue runners and grunts.

Most successful bait fishing results from looking for the bait schools, both with fishfinder and by scanning the sea surface, and also looking for telltale bird activity. One or more hovering royal terns, occasionally dipping or diving in the vicinity of Hawk Channel, is a sure sign of pilchards--so are diving pelicans.

Once you find them, motor upcurrent and drop balls of sand/chum mixture downwind, drift quietly into position, and cover the sand with an artistic, pancake-shaped throw of a 12-foot cast net.

What if, despite your best efforts, you've only caught 30 pilchards, or, worse, none? As long as it's not too late in the spring, go to the reef edge and scout for ballyhoo by riding along as high as your boat allows you to safely stand until you flush a sizable school, back off the throttle, toss the chumbag over and make a large circle before anchoring to wait them out. As they first appear in the chumslick, float back some hair hooks with tiny pieces of bait two feet or so behind a small clip-on bobber. Hair hook as many as you can (these will outlive most of those cast netted), then throw the net when they get close enough.

Live ballyhoo slow-trolled or drifted well back from your boat will attract some of the biggest blackfins over the seamount. Use a 5/0 Mustad 94150 hooked through the skin just aft of the beak and 30-pound leader, and drop back longer. Use the same technique if you don't have enough pilchards to chum.

Although livebaiting is the most popular method on the Hump, it isn't the only way to score. In fact, there are times during the October through May season here that it may be a better battle plan to skirt the crowds of livebaiters and work some artificials.