Like any cautious professional, Jesse Stoner doesn't like bold predictions. "But I'd have to say if you could pick a day to catch big bass, this is it," he said when we met at Angie's Truck Stop alongside the rolling Susquehanna last week.

The breeze was gentle and temperatures were headed their highest in months, with 60 degrees expected inland. River level was still up but falling from near-flood a few days earlier. Water color was perfect, stained but not muddy. Water temperature was just above 40 as a weak spring sun beamed down. Showtime!

"We're not going far," said Stoner, one of five guides who work the Susquehanna part-time for Fishin' Fools Guide Service out of Harrisburg, Pa. He opened up the 115-horsepower Yamaha jet-drive on his 18-foot aluminum bass boat only briefly to speed downriver from Montgomery Ferry before throttling back into a sleepy eddy on the west bank

"See those dark rocks?" he said, pointing to scree that had tumbled down the embankment from an expansion project on Highway 15. "They run right down into the water and heat up faster than anything else. Bass hang there, out of the current." A few dozen casts later we had proof.

The underwater scene we plumbed with small hair jigs and soft-plastic grubs is a classic for early spring smallmouth fishing, and the Susquehanna over the last decade has become one of the hottest spring fisheries in the East. Bass emerge from their winter torpor as soon as water temperatures rise and head to slack-water eddies to wait for nourishment to drift past. Bigger bass claim the best spots.

Prime eddies are easily identified. On a wide, swift river such as the Susquehanna they show up as slick patches of still water behind obstructions. If a fallen tree pokes out from the bank, a small eddy forms downstream that might hold a bass or two; a large rock or small island in midstream forms a larger slack-water eddy that could hold a dozen; a rocky peninsula such as the one we slipped behind forms a big eddy that might hold 100 bass.

Of those, we only managed to catch about 40 on one of the most successful days of bass fishing I can remember. The average size was about two pounds, a whopper of a smallmouth by most standards, and practically none were under the 15-inch minimum keeper size (though we released them all anyway). The biggest was a bronze-backed 6 1/2-pounder that Mark Susinno hooked on the last cast of the day and gingerly fought to the boat on eight-pound test line.

It was the biggest smallmouth ever for Susinno, a veteran member of the Potomac River Smallmouth Club who paints fish scenes for a living, owns his own jet boat and has been probing rivers in the mid-Atlantic for big bass in early spring for years. Never a big talker, Susinno was briefly struck speechless by the feat.

The 40-odd fish he, Stoner and I plucked from the big eddy were among 59 we caught in total that memorable day, all on small artificial lures, mostly small hair jigs Stoner ties using black doll's hair he buys from a toy supplier. Meantime, angling rivals Harry Weiland and Larry Coburn probed waters upstream of Montgomery Ferry in Weiland's jet boat and came back crowing about their success -- 46 bass, most in the two- to three-pound range.

The total was 105 bass. "Not bad for February," said Weiland as we drove back to Maryland through the coal-black night with boat in tow. "The only thing missing," said Susinno, "was the horizontal snow and 30 knots of wind we usually have."

Susinno, who lives in Olney, and Weiland, from Point of Rocks, Md., used to fish the upper Potomac for smallmouth in early spring, and still do to a lesser extent. But massive flooding two winters ago damaged the home river and bass fishing has been off. There are some positive signs. Weiland said he was out two weeks ago and caught several decent bass, his best spring outing since the floods.

Meantime, the bass community has discovered the Susquehanna two hours' drive north and its treasures are hard to resist. The average size of bass is better than just about anyplace south of Maine's Lakes Region or the Boundary Waters of Minnesota. Moreover, it's an attractive and accessible place, where even bank fishermen stand a chance of catching a whopper when conditions are right.

Stoner grew up around Selinsgrove and Harrisburg fishing from the banks. The Susquehanna always has been productive, he said, but only recently with the development of jet-powered bass boats has it been so accessible. And spring is prime for the jet boat crowd, when the river is high enough to zoom across rapids that later will be too rocky to navigate, and when big bass emerge to snap at lures.

The fishing isn't easy. Bass are not too aggressive in the cold water and you have to practically hit them on the nose for a strike. It means slow-rolling small lures just off the rocky, snag-infested bottom, which means losing plenty of tackle till you get a feel. It took me half a day, then I was whacking and stacking them right along with the experts.

But all the action wore me down and I quit too soon. I'd snapped off my dozenth hair jig on an underwater structure, the sun was sinking and I took a seat, thinking the bite was over. That's when Susinno tossed behind a rock and set the hook on the fish of a lifetime. Excellent smallmouth fishing should continue into May on the Susquehanna, including a 10-day period in April when locals say females on the spawning beds whack spinnerbaits so hard it hurts an angler's arms. CAPTION: Smallmouth bass are plentiful during the winter in the Pennsylvania stretch of the Susquehanna as Jesse Stoner, left, and Mark Susinno are well aware.