iSIMANGALISO WETLAND PARK, South Africa—Themba Mkhonto was thigh-deep in the warm water of Kosi Bay, an estuary near the Mozambique border, when I waded 100 yards from the shore to talk to him. He was repairing his fish trap, which he told me had belonged to his father and his grandfather before him.

Fish trapping is a centuries-old tradition here. No bait is involved. The fish follow a brushwood palisade, curved like a hook, that guides them into one or more circular pens, called kraals. They get into the kraal through a cunning gate made of crisscrossed sticks; easy to enter, hard to exit.

Once inside, large fish cannot escape, but small ones can squeeze between the stakes of the kraal, which are tied with thick fiber stripped from the leaves of wild banana palms. Each day, the trap owner climbs into his kraals and spears any fish that arrived overnight.

Mkhonto called the ones that get caught "stupid fish," but he said it gently, as if to ask who among us has not made a stupid choice. "They could swim up the channel, but instead they come into my trap," he said, with mild amazement.

I asked Mkhonto why he fished with a trap and not with a more efficient method, such as a gill net. With a trap, he said, you catch one fish, or two, or three. With a net you might catch ten, 20, 50. "Not good for me," he said, including himself in the sustainability equation.

Mkhonto's sense of proportionality is no longer the norm. The collapse of the migrant labor system at the end of South Africa's apartheid era in the 1990s sent a flood of unemployed workers back to their homelands on the coasts. Jobs were scarce, so the returning workers asked the indunas, the local sub-chiefs, what to do.

"Build a trap," the indunas said. "Catch some fish."

Today the estuary looks like a fish-trap maze, and I wonder how any fish at all swim that gantlet. There are even more traps upstream, in some of the four adjoining dune lakes.

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Many of the new fishermen have built traps with nontraditional materials: bamboo and eucalyptus poles tied with nylon twine, instead of twisted branches bound with thick lashings. The modern traps have narrower gaps that prevent undersize fish from escaping.

The biggest problem, however, isn't trap density and gap size, but changing attitudes, said Scotty Kyle, a fisheries scientist who has been studying the lake-and-estuary system and its idiosyncratic traps for 30 years.

"A subsistence fishery mostly run by old men subsidizing their pensions has become a youngster-driven commercial fishery using modern materials," said Kyle, as we sat outside his house in a forest glade overlooking the largest of the Kosi lakes, enjoying coffee and bullet-hard biscuits called rusks, a South African specialty. "Some of these traps are big commercial concerns. The people running them have 4x4 vehicles and are exporting the fish out of the area."

Of particular concern to Kyle is a new practice of building traps that face downstream and catch fish on their way up to the lakes. Traditionally, the palisades faced upstream and caught fish only after they had matured in the lakes and were on their way back to sea to spawn.

View Images EMILY M. ENG, NG STAFF; EDWARD BENFIELD. SOURCE: SCOTTY KYLE

"Now the fish get smashed on the way out to the spawning grounds, and get smashed on the way back in," said Kyle. "It's a double dip, and it's catching undersize fish and lots of them."

The average length of grunter, one of the main species caught in the traps, has almost halved since Kyle began his work. In his view, the trade-off between the community and iSimangaliso Wetland Park—a low-impact subsistence fishery in a conservation area—has been compromised. To put it another way, there are not enough Mkhontos.

"Sadly, people like him are being pushed aside by others who ignore their neighbors and the good of the environment for personal gain," Kyle said. "This is a worldwide phenomenon that has only recently begun to take hold at Kosi Bay."

Mkhonto himself didn't know how to solve this problem. Kosi Bay's traditional governance system based on community obligation and customary law has struggled to constrain individual self-interest. "To control fishing is the right thing," he said. "But the government must talk to the people. The government must remember that the people suffer every time."

My conversations with small-scale fishermen throughout South Africa invariably circled back to the suffering created by colonialism, apartheid, and ongoing government indifference. When Kosi Bay became a nature reserve in 1952, and was later expanded in 1987, Mkhonto's people, the Thonga tribe, were told that they could no longer live by the sea. They were moved inland.

To Mkhonto, the displacement was illogical as well as immoral. His people have never accepted the idea that conservation areas should exclude humans. In earlier times, he said, hippos foraging around the lakes occasionally trampled the fish traps. People accepted this.

"The people stay here with the hippo," said Mkhonto. "The people still alive. The hippo still alive. We stay together. Then the nature conservation come and say, 'It is my hippo. You must go away from here.'"

View Images Themba Mkhonto repairs a fish trap in Kosi Bay, an estuary near the Mozambique border. Photograph by Kennedy Warne

People in the village of eNkovukeni, perched on dunes between the Kosi lakes and the sea, refused to move. I walked there with two boys I'd met in the town of Manguzi. We followed a path through hippo grass, wading in water the color of cognac, and crossed a ribbon of land that separated two lakes.

We stopped at the hut of a man named Titus, who took his fishing rod and led us across the dunes. As we walked we picked and ate pale marula fruits and purple sea grapes. The boys chased insouciant blue-and-yellow butterflies that danced from bush to bush.

At the coast, Titus dug in the coarse sand for ghost crabs to use as bait. He walked out on the black-rock reef, where the swells of the Indian Ocean sent up curtains of spray. He stood a long time, squinting against the light, watching the curl of the green waves and the gray shapes of fish.

"I want them," he said, and cast his line into the breakers.

These people revere the sea. They believe their ancestors reside there, and they ritually drink seawater to imbibe its cleansing, curative essence.

"This is what we think," Mkhonto told me as we sat under a shade tree beside his home. "If the sea stops, the people die. My father say, 'Listen to me, my son. Do you want to know who is God? There he is.'"

The people have a christening tradition that affirms their bond to the ocean. A newborn baby is placed on the wet sand. Just as a wave is about to wash over it, the mother scoops it up to safety. Presenting a child to the sea instills bravery and devotion, Mkhonto said.

"Does this still happen today?" I asked him.

He replied: "It happened to me."

As enviable as that sense of connection to the sea may be, the decline of Kosi Bay's fish stocks tells a different story—or perhaps a variation on a worldwide story, one about failing to live within ecological limits.