- Researchers blame an increase in illegal fishing for the decline of sea cucumbers in a remote Australian marine park and say many other reefs in the country have also been affected.
- The Australian government has launched an operation to crack down on illegal fishing in the country’s Northern Territory where the problem is acute, including for high-value sea cucumbers.
- But as long as the market for sea cucumbers remains strong in China and other East Asian countries, experts say, wild populations of this slow-growing animal could collapse and put the health of reef systems at risk in Australia and beyond.
Off the northwestern coast of Australia, in some of the world’s most pristine and diverse coral reefs, sea cucumbers are rapidly vanishing.
Overall populations of these tubular, blobby animals declined by more than half from 2018 to 2023 in the Rowley Shoals, a remote Australian marine park, according to a recent survey. Some especially vulnerable species, such as the pineapple sea cucumber (Thelenota ananas) and the hairy blackfish (Actinopyga miliaris), have disappeared across most or all of the monitoring sites there.
Researchers believe a boom in illegal fishing is to blame. Sea cucumber harvesting is prohibited in the Rowley Shoals, and the survey found Australian authorities caught 112 fishing vessels in the area carrying a collective 22 metric tons of sea cucumbers between 2021 and 2023, a figure that translates to roughly 33,000-45,000 animals. This is just the share of illegal fishing that authorities managed to intercept; the researchers noted that the actual sea cucumber body count is likely much higher.
The problem isn’t unique to Rowley Shoals. It occurs in reefs across the country’s western and northern waters and has recently been on the rise, according to several researchers interviewed by Mongabay, driven by demand for the animals in China and other East Asian countries where they are considered a delicacy and used in traditional Chinese medicine.
Illegal sea cucumber fishing spiked in northern Australia in 2024, according to experts, with fishers targeting sanctuaries and internationally protected species. The Australian government responded by launching Operation LUNAR at the end of 2024 to crack down on illegal fishing by foreign vessels in the country’s Northern Territory, where the problem is acute, including for high-value sea cucumbers. More than 100 foreign fishing vessels have been intercepted since, according to the Australian Border Force (ABF). Dozens of foreign fishers, primarily from Indonesia, have been arrested in connection with fishing illegally in Australia, their sea cucumber catches confiscated and equipment destroyed.
“Enforcement activity under Operation LUNAR has strengthened ABF’s ability to detect, deter and respond to incursions earlier and more effectively across northern waters,” an ABF spokesperson told Mongabay in a statement. The operation reinforces efforts to “safeguard Australia’s marine resources and support the long‑term sustainability of northern ecosystems,” the statement said.
Vital nutrient dispersers
But as long as demand for sea cucumbers remains strong, wild populations of this slow-growing animal could collapse and put the health of entire reef systems at risk in Australia and beyond, experts said.
“We’re just starting to learn how important they are,” Alison Hammond, a sea cucumber researcher at Australia’s University of the Sunshine Coast, told Mongabay.
She said these “little turd-looking animals” — a kind of echinoderm, like starfish and sea urchins — recycle detritus, sediment and algae. This can help disperse nutrients, improving the strength and resilience of coral reefs, seagrass beds and marine ecosystems broadly. When sea cucumbers disappear, seagrass becomes thinner and weaker. Mats of algae can bloom, choking out a reef. “These effects can be way down the line,” Hammond said, affecting reefs long after the sea cucumbers are gone.
Easy pickings for poachers
The disappearances can be sudden. Because sea cucumbers are harmless to people, generally stationary and tend to gather in groups, they are easy to harvest en masse. Many of the most highly sought species occur on shallow, easily accessed reefs. “You just pick them up, put them in a basket and keep going,” Teale Phelps Bondaroff, who studies illegal sea cucumber fisheries and serves as the research director of the Hong Kong-based advocacy group Oceans Asia, told Mongabay.
With high demand and big profits — for example, the endangered Japanese spiky sea cucumber (Apostichopus japonicus) can retail for more than $3,500 per kilogram ($1,625 per pound) — illegal sea cucumber fishing is a global problem. India banned sea-cucumber fishing entirely more than two decades ago, and Sri Lanka implemented a permitting system, but the waters between the countries remain a hotspot for sea cucumber poaching. Ecuador, including the Galapagos Islands, has also seen illegal sea-cucumber fishing for decades, with populations dropping so low the practice is no longer economically viable. Authorities in Madagascar and Mexico have even reported deaths in recent years as fishers dive deeper in search of vanishing sea cucumbers.
Despite the dangers, the sea cucumber trade continues to attract desperate fishers and the organized crime syndicates they often sell to, including yakuza gangs in Japan, according to Bondaroff. They are lured by the low risk of getting caught and the high price sea cucumbers fetch relative to other kinds of illegal wildlife, drug or arms trafficking, he said.
Today, Indonesian fishers illegally harvesting sea cucumbers in Australian waters are often “people looking for economic opportunity,” Felix Morrow, a researcher at Memorial University of Newfoundland studying international fisheries management, told Mongabay. Their catches usually get fed into organized crime networks that have diversified into the wildlife trade, which “smuggle them into end markets” like Hong Kong, he said.
Historically, however, Indonesian fishers have collected sea cucumbers from some reefs for centuries, before the waters came under Australian control, according to a 2025 paper. A 1974 Memorandum of Understanding between the countries allowed the traditional practice to continue, though sea cucumber fishing was later restricted in some areas due to overharvesting concerns.
The road to recovery
Sea cucumber populations often struggle to recover from overfishing. As animals that can live for decades with few natural predators when fully grown, they don’t reproduce often. When they do, they mate via broadcast spawning, gathering in large groups to release eggs and sperm into the water simultaneously. When an area is left with too few individuals spread out far from each other, they cannot reproduce.
“It’s really difficult to have any form of sustainable sea cucumber fishery, just because of the nature of the animals,” John Keesing, a research scientist at the Commonwealth Scientific and Industrial Research Organisation and a co-author on the Rowley Shoals survey, told Mongabay.
On the other side of the continent from Rowley Shoals, Hervey Bay — part of Australia’s Great Sandy Marine Park — is an example of what happens when these fisheries completely collapse. When Hammond, first started interviewing locals there, she said the consensus was that the bay never had sea cucumbers. But when she interviewed elderly fishers, they described a different environment in decades past: millions of sea cucumbers lining the bay’s seagrass carpets. She said one man remembered he “couldn’t pull his nets up because they were so full of sea cucumbers, it was just too heavy.”
That is no longer the case. Hammond has spent more than a year searching for the endangered golden sandfish sea cucumber (Holothuria scabra) in Hervey Bay, enlisting dozens of community members and local fishers. They found just two.
Hammond said she hopes to ultimately see a captive breeding program reintroduce sea cucumbers into the bay, which is noticeably less healthy than surrounding areas that still have the animals. But a lack of specimens would complicate these efforts. While countries like Tanzania have encouraged commercial captive breeding and “ranching” efforts that allow locals to reap the economic benefits, Hammond said sea cucumber husbandry hasn’t been implemented purely for conservation purposes.
The better path, according to experts, would be to stop overfishing and illegal sea cucumber catches before they destroy local populations. But given the size of Australia’s coastline and territorial waters, patrolling them is an expensive prospect. “Your chances of not getting caught if you’re an illegal fisherman are unfortunately pretty good,” Keesing said.
Still, he said monitoring populations and enforcing regulations are important, especially in otherwise healthy marine parks like Rowley Shoals.
“We have some of the last pristine populations of sea cucumbers,” he said. “Protecting them is paramount.”
Banner image: A pineapple sea cucumber (Thelenota ananas). Image © Julian Jimenez via iNaturalist (CC BY-NC 4.0).
Down on the ranch with Mafia Island’s free-range sea cucumbers
Citations:
Keesing, J., & Bessey, C. (2025). Local extinction of golden sandfish at Ashmore Reef, northwestern Australia. SPC Beche-de-Mer Information Bulletin, 45, 76-81. Retrieved from: https://www.spc.int/DigitalLibrary/Doc/FAME/InfoBull/BDM/45/BDM45_76_Keesing.html
Keesing, J. K., Bessey, C., Mortimer, N., Hosack, G. R., Haywood, M. D., Orr, M., … Edgar, G. J. (2025). Status of coral, giant clam and sea cucumber communities including CITES listed species on a remote Australian coral reef atoll and the potential impact of illegal fishing. Marine Environmental Research, 204, 106915. doi:10.1016/j.marenvres.2024.106915
Leal, I., Ross, C. L., Strydom, S., Evans, R. D., Holmes, T. H., Edgar, G. J., & Keesing, J. K. (2026). Widespread decline in the abundance of sea cucumber assemblages in atolls of the protected Rowley shoals, northwestern Australia. Limnology and Oceanography Letters, 11(2). doi:10.1002/lol2.70100
Purcell, S. W., Williamson, D. H., & Ngaluafe, P. (2018). Chinese market prices of beche-de-mer: Implications for fisheries and aquaculture. Marine Policy, 91, 58-65. doi:10.1016/j.marpol.2018.02.005
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Cite this article
Madeline Shaw (2026). Illegal fishing takes a toll on Australia’s sea cucumbers. Mongabay Conservation news. DOI: https://doi.org/10.66709/news-322747
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