- Sea cucumbers are prized as a delicacy in East Asia and used in some forms of traditional medicine.
- Because of the high demand for them, their populations have fallen off a cliff in Tanzania and elsewhere, landing many species on the IUCN’s red list.
- After banning exports from mainland Tanzania in 2003, the government has recently begun to encourage sea cucumber farming and ranching.
MAFIA ISLAND, Tanzania — His white beard streaming in the turquoise waters, Waziri Mpogo dives under the surface a few hundred meters offshore of a palm-lined beach. Holding his breath, he heads for the seagrass below, emerging with a slimy yellow tube in his hand. It’s prickly and thick, about 15 centimeters (6 inches) long with a small hole at one end. He points at it excitedly as he swims back up.
This is a sea cucumber — a Thelenota ananas, or “pineapple” sea cucumber, to be exact. It’s one of hundreds that roam free-range on the seabed here at Mpogo Ocean Ranching Ltd, off the coast of Tanzania’s Mafia Island. It might not look like it, but this slug-like bottom-feeder is one of the most valuable species in the East African ocean. Because of that, it’s been poached to the edge of extinction here and across the world. This 67-hectare (166-acre) underwater ranch is part of Tanzania’s efforts to get the sea cucumber trade under control and help their population recover.
Mpogo holds the undulating cylinder above the surface, grinning. He’s 67 and heavyset with an elder’s bearing, but in the water he’s almost childlike, darting in and out of the seagrass and teasing crabs as he tracks down his herd, which he deposits into a bucket on a small boat nearby. They call him the “father” of sea cucumber ranching here, and his business is his passion.
“Sea cucumbers are an endangered species,” he says, waves lapping at his chin. “With this project that I started, I’m hoping to increase their numbers.”
Most of the 65,000 people who live on Mafia Island survive off the ocean in one way or another. Quieter than its tourist magnet cousin to the north, Zanzibar, it’s still a world-class dive and snorkel destination, known for its whale shark tours. Fishing villages dot the white-sand coastline along with single-engine boats their inhabitants use to earn their living.
Lately it’s been harder to get a good catch, though. Overfishing has caused stocks to plummet, forcing fishers further out to sea. These sea cucumbers might be part of the solution.
Mpogo’s offshore ranch was founded in 2023, but the sea cucumber business isn’t new to East Africa. The arrival of Chinese traders in the 1970s kicked off a booming trade in the echinoderms, a category that includes starfish and sea urchins. After being slow-smoked and dried over an open flame, they’re shipped to East Asia, where they’re a culinary delicacy, known as bêche-de-mer. Sometimes they’re also ground into a powder and used to treat impotence, fatigue, and other medical conditions.
The soaring demand for sea cucumbers padded the accounts of Tanzanian traders, but by the 1990s their population had collapsed. In 2003, the government implemented a ban on exports from the mainland after researchers realized the extent of the decline.
Tanzania wasn’t the only country facing this problem. Today, most valuable sea cucumber species are endangered and on the IUCN’s red list. When threatened, they can regurgitate part of their intestines to scare off predators. That might work on crabs and small fish, but for humans it’s just a sticky nuisance. Slow-moving, easy to spot and even easier to catch, in coastlines across the world they’ve been virtually wiped out.
In East Asian markets, dried sea cucumbers can fetch exorbitant prices that reach hundreds of dollars per kilogram for some species. These big payouts have created a thriving black market and turned the trade in them into serious business. In Japan, yakuza crime families are involved, and there have been reports of gun battles at sea between rival fishers on Mexico’s Yucatán coast.
Their disappearance from coastal and other underwater ecosystems has an environmental cost. As “bioturbators,” they till the seabed, helping to fertilize the growth of seagrass and seaweed that feeds other species. Some research shows they play a role in keeping coral reefs healthy.
“They transfer nutrients from the top layer to the bottom of the substrate, and [that] helps the benthos that’s found in seagrass and coral reef ecosystems flourish,” says Victor Kaiza, an aquatic ecologist and aquaculture specialist at Tanzania’s Fisheries Education and Training Agency.
Despite its strength on paper, Tanzania’s export ban wasn’t robustly enforced, and it had a major loophole: Zanzibar, which is a semi-independent island with a degree of autonomy, was exempted. Traders there, long the middlemen with East Asian importers, didn’t stop buying illegally harvested sea cucumbers from the mainland.
“People already tasted the money,” Kaiza says. “Sea cucumber harvesting and fishing was being run like a cartel in most parts of mainland Tanzania.”
As prices climbed in the late 2010s, the Tanzanian government decided it had to do more to bring the trade out into the open where it could be better regulated. In 2019, it began encouraging offshore farming operations like Mpogo’s, providing training to would-be sea cucumber entrepreneurs, and offering a pathway to export licenses for the first time since the 2003 ban.
Kaiza trained around 300 people to set up the farms. Dozens opened on the mainland. Mpogo’s was the first on Mafia Island.
The idea for the ranch was planted decades ago. As a teenager, Mpogo knew a Chinese trader who worked on Mafia Island. The man taught him how to smoke sea cucumbers and prepare them in dishes. Mpogo liked how they tasted – a bit like octopus or shellfish.
His friends and neighbors aren’t as enthused. The word for sea cucumber in Swahili is jongoo bahari, which roughly translates to “ocean millipede.” It’s not exactly appetizing branding, and when he offers to cook it for his guests, they usually decline.
“People hate it because of the name,” he says. “Even my family doesn’t like it because of that.”
Shaky local reviews aside, the sea cucumber trade between East Africa and East Asia is doing a healthy clip, for better and for worse. According to the advocacy organization TRAFFIC, between 2012 and 2019, the top five East African producers shipped more than 3 million kilograms (6.6 million pounds) of dried sea cucumber to Hong Kong alone. Tanzania accounted for a little under 500,000 kg (1.1 million lbs) of that sum. Each kilogram has somewhere around 20-30 individual sea cucumbers.
When Mpogo heard the government was going to make farming them legal outside of Zanzibar, he reached out to his business partner. The two were coming off of a failed cashew farming operation on Mafia Island, but this looked like a more promising opportunity.
They asked the leaders of Bongo village, where his ranch operates, for permission to set it up. At first, they gave him a small, ten-acre patch of coastline. The two entrepreneurs sourced 20,000 newborn sea cucumbers, called “fingerlings,” from a nursery on the mainland at around 15 cents apiece to start the ranch. Their efforts raised a few eyebrows around town.
“Some people, even government officials, don’t understand what he’s thinking,” says Aboo Nasibu Chapa, a banker with Mafia Island’s CRDB branch who’s been advising Mpogo and his business. “There are people who are saying he’s mad, he’s getting old with a lot of problems. They don’t see what he is seeing.”
Undeterred by his skeptics, Mpogo built up the ranch’s operations. He had a slightly different approach than other sea cucumber farms – at his, they weren’t enclosed by a fence.
Calling himself a conservationist at heart, he scowls at the idea of trapping his sea cucumbers into a small space. By allowing them to have an open range that’s not blocked out from the rest of the ocean, the underwater ranch has the look of a thriving ecosystem. Sea turtles and puffer fish drop in to feed, cruising above the meadow of seagrass where his five species of sea cucumber use their tiny tube feet to graze the sediments below.
Bongo’s leaders were impressed with the health of the ranch’s ecology, which was attracting fish and other sea life. They decided to give him the right to use more of the town’s coastline.
“[Sea cucumbers] can’t be domesticated like sheep or camels or hens,” he says. “They need human protection, but if you restrict them to one place and fence it, you deprive them of important aspects of life. In some stages they need sun rays, and in others they need to be in the deep ocean.”
His unfenced ranching technique is ecologically friendly, but it presents the business with other problems. In the long-run, Mpogo wants his ranch to be an example for people on Mafia Island, showing them that sea cucumber rearing is a sustainable way to earn a decent living. Eventually he plans to sell fingerlings to his neighbors, which they can use to set up their own businesses.
In the meantime, though, he spends a lot of money keeping some of those neighbors out.
Local people are allowed to bring their boats onto the ranch to catch fish, but his sea cucumbers are off-limits. That doesn’t stop people from trying to snatch them anyway. At night, divers try to slip in on poaching missions. He’s spent many nights on his boat waiting to catch them, and when he’s not there, he pays security guards to keep intruders out.
“Theft is still on the rise, due to the shortage of these valuable creatures,” he says.
The costs of setting up the ranch are adding up. So far, he and his partner have spent around 230 million Tanzanian schillings (around $85,000). They have a permit to farm and harvest their sea cucumbers, but they’re waiting on the government to give them final environmental approval for the operation.
“It’s among the endangered species, so they need to minimize and control how people deal with these sea cucumbers. You need their permission to harvest and export so they can track exactly what’s going on and how much you’re producing,” Chapa says.
Back on shore, Mpogo dumps a sack of dried cucumbers onto a table in a small shack. In the ocean, they’re supple and soft to the touch, gently molding themselves around the shape of your hand when picked up. These ones, processed and smoked, are leathery and tough.
The two partners are waiting on environmental and export permits that will allow them to sell these to the right overseas buyer. Then the sea cucumbers will be packaged up and shipped to markets in Hong Kong or Shanghai, where they’ll end their journey on a dinner plate or inside a medicine jar.
“I think he’s going to make a lot of money,” Chapa says.
Mpogo carefully arranges the sea cucumbers into piles, explaining the price each should fetch: $350 per kilo for “grade one” jongoo mchanga, $250 for jongoo spinyo. It’s a labor of love, but it is labor, and he wants to see a return on the investment. But if he can help sea cucumbers make a comeback on Mafia Island in the process, that’s even better.
“My dream is to make this project the best in Africa so that more researchers come here to help us improve it,” he says. “It’s a good place, the fish are peaceful, and I love it because of this. I don’t want to see the fish or sea cucumbers drying up.”
Citations:
Mercier, A., Purcell, S. W., Montgomery, E. M., Kinch, J., Byrne, M., & Hamel, J. (2025). Revered and reviled: The plight of the vanishing sea cucumbers. Annual Review of Marine Science, 17(1), 115-142. doi:10.1146/annurev-marine-032123-025441
Floren, A. S., Hayashizaki, K., Putchakarn, S., Tuntiprapas, P., & Prathep, A. (2021). A review of factors influencing the seagrass-sea cucumber association in tropical seagrass meadows. Frontiers in Marine Science, 8. doi:10.3389/fmars.2021.696134
Williamson, J. E., Duce, S., Joyce, K. E., & Raoult, V. (2021). Putting sea cucumbers on the map: Projected holothurian bioturbation rates on a coral reef scale. Coral Reefs, 40(2), 559-569. doi:10.1007/s00338-021-02057-2
Banner image: Waziri Mpogo of Tanzania’s Mafia Island places sea cucumbers from his ranch into a bucket. Image by Ashoka Mukpo for Mongabay.
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