Few people associate fishing in Florida with the Ice Ages, but the Delphs of Key West routinely fish along ancient shorelines from the Paleolithic Age, when most of our hemisphere was covered in ice, oceans were shallower and continental Florida extended miles farther out. These days, those shores are under hundreds of feet of sea, and from their depths, the Delph family and other adventurous anglers reel up snowy and yellowedge grouper, rosefish, tilefish and other species, all on conventional rod, reel and jigs.

A 9-ounce jig for probing the fathoms.

Anglers familiar with jigging for seatrout in 20 feet, or for muttons in 120, may be skeptical about the prospects of working a jig along the bottom in 300 to 1,000 feet. Certainly it takes the right combination of tackle, conditions, spots and presentation to be successful, but the principles are the same as drifting and jigging in that shallower water. Super-deep jigging, or as Ralph Delph calls it, “deep pulling,” takes the same technique, and our equipment and our expectations, to their known limits.

Ralph and his sons Rob and Billy showed me how surprisingly easy it can look on a recent bright day off Key West. We spent a few short, sweet hours drifting over known wrecks and along those deep shorelines, while hooking up constantly and keeping the islands in plain sight. We had a three-quarter waxing moon, 10-knot wind from the east, a current trickling to the east in most locations and good, clear purple water, the kind that’s full of nutrients to get fish feeding.

“Most guys troll out here,” Ralph Delph said, gesturing to the blue water ahead of us. “They’d never even think of jigging. That leaves this water untouched, where all the fish are. It’s a rich fishery, and one that stays consistent through the year, even during the doldrums of summer, because nothing much changes down there.”

“At 600 feet,” he continued, “the water temp is in the low 50s, around 52. We have friends who dive to 300 who tell us that there’s a lot of available light at that depth, but down deeper, there’s probably not much light, but the fish are used to that.”

Essential to jigging deeper than 300 feet is the use of small diameter braided line. This cuts through water and current to allow jigs to hit and hold bottom, even in windy conditions when boats drift quickly. Braid has a higher breaking point than monofilament of equivalent diameter, and you can pack more of it on the spool to reach the depths. More importantly, there’s no stretch compared to monofilament. That means that a 6-inch lift on your rod pulls the jig six inches, even at 500 feet and more, so that you can set the hook accurately when you feel the hit. Monofilament by comparison has about 20 feet of stretch per 100 feet of line when you’re fighting a fish. So, at hundreds of feet, the angler with mono is only taking stretch out of the line for the first crucial seconds of the fight, not even fighting the fish, says Ralph. By that time, you can imagine that the grouper has wrapped you twice around nearby structure, run back to his hole and fallen asleep.

“There’s no way you could fish at these depths with regular mono,” Ralph says. “With the braided line, you’ll feel the bottom at 600 feet and more, no problem.”

The Delphs drift over their chosen grounds; it’s out of the question to anchor in such depths.

At our first spot, 325 feet deep, Ralph checked the depthfinder for activity, and at his word, Billy made the drop.

“You watch the fish on the screen and when he’s at his pinnacle, you drop,” Ralph said, “because that’s as close as you’ll get to him, and he’ll be farthest from his holes.”

Ralph didn’t care much for the activity showing on his screen. He suggested that he’d pull away while Billy reeled to put tension on the brand new line and pack it tightly on the spool. Braided line is so thin that it can slip under itself on the spool and cut if it’s too loosely packed.

After 30 seconds, Billy announced, “I’ve got a fish,” and a minute later, as we kept moving, he hauled aboard a blackfin tuna that had grabbed the jig as it moved up the water column.