A Nicaragua rapids some 100 meandering miles upstream from the sea would seem to be an unlikely spot to catch tarpon. But each year—from March to June—great schools of the huge, silvery fish roll in the rocky shallows of the murky San Juan River far from its mouth in the Caribbean. Why they seek out these tepid rapids remains a mystery—tarpon spawn in brackish coastal waters—and their behavior is equally enigmatic. These seemingly strayed tarpon strike readily at artificial lures, and in a day's fishing an angler can hook and fight as many as 50 on slow-sinking plugs cast into the fast water (right and following pages). In some ways it is a strange place to fish. Orchids ornament the jungle trees and the forest is noisy with the cries of Congo monkeys and the chattering of parrots. But even in this exotic setting, nothing is quite so memorable to the angler as the sight of a 100-pound tarpon arcing up out of the water in a twisting, spray-showering leap—a flash of silver against a backdrop of lush vegetation.

The fishermen who visit the San Juan River are few—a handful of Nicaraguan sportsmen and the local Indians. When Artist Tom Allen and four fishing friends arrived at El Toro Rapids last May, they quickly discovered how uneducated the tarpon were. It was obvious they had never seen a plug before. At the end of five days of fishing the visitors had fought hundreds of tarpon from 20 to 100 pounds. Most of the fish were on just long enough to make a few spectacular jumps. "Those that hooked themselves," explains Allen, "simply turned on the power and bored downriver into the shallow rapids, leaving us with two choices: we could break them off and lose plugs and line, or we could crash down through the rapids and continue the battle below in calm water. We lost a lot of plugs and line." The few fish that they managed to keep out of the rapids—and away from the slashing jaws of the seven-foot freshwater sharks in the river—were given to the Indians, who grind the fish up into tarpon sausage.

The San Juan is surprisingly accessible to anglers, and at bargain rates. Five days of fishing, plus round-trip air fare, guides and lodging cost Allen and his friends less than $500 each. They took a Lanica Airlines DC-6 from Miami to Managua north of Lake Nicaragua, where they met their outfitter, Alfredo Bequillard Jr. They then flew in three chartered Cessnas over the lake to San Carlos, where they transferred to outboard-powered dugouts for the 20-mile trip downriver.

The menu at camp—a gaily painted Indian farmhouse—was skimpy, but the food was hearty and well-cooked. The main dish was guatusa, wild pig shot by their farmer host and cooked with beans and rice on a portable kerosene stove. One night the expedition ate three unborn shark pups cut out of the belly of a female shark caught with parachute cord, a hook baited with tarpon and a five-gallon gas can that served as a buoy. The tender white strip down the backbone tasted like grouper.

"We swam in the shallow, spring-fed tributary streams, spent four hours taking a siesta in the middle of each day and enjoyed the jungle noises," says Allen. "It was better than the sound track of an old Tarzan movie."

ILLUSTRATIONTOM ALLEN ILLUSTRATIONTOM ALLENAnchored above a rapids, an Indian boy in a dugout plays a wildly leaping tarpon on a handline while his friend waits to gaff it with a harpoon. TWO ILLUSTRATIONSTOM ALLENAfter a morning's fishing (top left), Allen and his friends stop at a plantation for drinks in a hibiscus-shaded patio.