- A recent study provides the first large-scale map of Cambodia’s coastal habitats and reports early seagrass recovery near anti-trawling structures in the Kep Marine Fisheries Management Area.
- Surveys across 62,146 hectares (153,566 acres) show a 39% loss of seagrass cover in Kampot province over the past decade.
- The study doesn’t examine potential impacts from the planned $1.7 billion Funan Techo Canal, which is set to meet the sea about 2.5 kilometers (1.6 miles) away from the Kep Marine Fisheries Management Area.
A recent study provides the first detailed map of Cambodia’s coastal seafloor habitats and finds that simple, low-cost anti-trawling structures are helping seagrass meadows recover and support small-scale fishers in the Kep Marine Fisheries Management Area in the Gulf of Thailand.
The study was published in Frontiers in Marine Science by researchers from Marine Conservation Cambodia, an organization that co-manages the Kep MFMA in partnership with Cambodian authorities and local fishing communities.
To map the region’s seafloor, the team surveyed 62,146 hectares (153,566 acres) across four areas: Kep MFMA, Outer Kep, Kampot, and Koh Seh. Divers visited hundreds of points spaced every 250 meters (820 feet) to document seagrasses, corals, shellfish beds, sediment type, and depth. In shallow waters, they used aerial photos to observe areas that boats couldn’t reach. The data were then analyzed using computer models to understand how depth and sediment influence habitat presence.
They found that seagrass cover in Kampot province declined by 39% between 2013 and 2023 — the first time this loss has been clearly measured. They described “destructive fishing” as the most immediate driver of habitat loss in Cambodia, alongside chronic pressures like warming seas and turbidity from coastal development (two large-scale ports and a special economic zone are under construction). The study said the decline in seagrass highlights “the urgent need for scalable restoration and enforcement strategies.”
Signs of hope
Across the total habitat surveyed, the researchers recorded 15,320 hectares (37,857 acres) of seagrass, coral and bivalve beds. Ten seagrass species were recorded.
The MFMA showed the highest diversity of seagrass and the earliest signs of regrowth, particularly near concrete blocks called fisheries productivity structures (FPSs), pioneered by Marine Conservation Cambodia, which are placed underwater to snag trawl nets and deter illegal fishing.
“The pioneer species Halophila spp. were observed in abundance in close proximity to FPSs, indicating regrowth in areas now protected from trawlers,” the study noted.
The authors describe FPSs as “a scalable, low-cost conservation tool” that could help other Southeast Asian countries with limited enforcement capacity. The structures have also been “positively received by small-scale fishermen,” the study said, because they help protect traditional fishing grounds from industrial trawlers.
These findings echo earlier reporting on Cambodia’s fisheries crisis. A 2023 Mongabay feature described how destructive bottom trawling has left some areas with “nothing else; no life, just mud, muck and death.” In several locations, seagrass beds shrank by more than 70% between 2017 and 2022. Around 40% of local fishing boats have stopped operating, and overall catch has fallen by at least 60%. MCC’s anti-trawling blocks were first tested in Kep, and there are now plans to deploy thousands more in 25 coastal communities.
The researchers acknowledged key limitations. The survey relied on free-diving and visual observations at 250-meter intervals and didn’t measure water quality or coral bleaching. “Despite the lower resolution, this study’s large sample size achieved wide-scale data,” they wrote. They recommended incorporating drones, acoustic mapping and remote sensing in future work.
The paper also found that depth and sediment strongly influence seagrass growth. Seagrasses were rarely found in deeper or muddy areas, a pattern the authors associate with reduced light availability and greater trawler accessibility.
Meanwhile, the study didn’t address how future coastal development projects, such as the ongoing Funan Techno Canal project, scheduled to be completed by 2028, may affect seagrass recovery or potentially reverse recent gains. China and Cambodia have agreed to build the $1.7 billion, 180-kilometer (112-mile) canal linking the Mekong River to the Gulf of Thailand via Kep province. Cambodia promotes it as a way to reduce reliance on Vietnamese ports, while Vietnam fears it could divert Mekong water flows and harm downstream farmlands.
More locally, the canal is set to meet the sea roughly 2.5 km (1.6 mi) from the northeastern border of the Kep MFMA, meaning the area is likely to be significantly impacted by dredging during construction and increased marine traffic once the canal is open.
Because the canal is a sensitive topic in Cambodia — with possible implications for coastal hydrology, sedimentation and fisheries — Mongabay asked the study’s authors and several external experts how such a project could influence the recovery documented in Kep and Kampot. The lead author didn’t respond by the time of publication, and only one expert agreed to comment, on condition of anonymity.
The expert said the study represents “a fairly robust monitoring regime in a non data-rich, relatively low capacity environment,” and agreed that visual surveys at this scale can show whether anti-trawling blocks have deterred illegal trawling. However, they noted that such methods are “unlikely to detect granular changes in benthic habitat cover.” Such limitations could become more significant if large-scale hydrological changes occur in the region, such as those potentially associated with the proposed Funan Techo Canal, which the study didn’t assess.
The expert also pointed to “key limitations,” including the study’s lack of engagement with structural drivers of illegal trawling.
They also questioned whether anti-trawling blocks work beyond the immediate area, asking if they function as “a national or regional scale intervention or purely a local one” and raising concerns about the potential displacement of illegal trawling. “There is no consideration of displacement effects in the study at all.” They added that “simply moving illegality or destructive practices to another place is a possible consequence of anti-trawling blocks.”
While the study offers an important baseline, the authors emphasized that “long-term monitoring is essential to track changes in habitat coverage over time,” particularly as FPS deployment and other pressures continue to shape the region’s coastal ecosystems.
Banner image: Marine Conservation Cambodia members deploy blocks from a raft to the seabed. Image by Matt Blomberg for Mongabay.
‘Mud, muck and death’: Cambodia’s plan to obstruct trawlers and revive local fishing
Citation:
Ho, A., Macdonald, M., Rétif, S., Lor, S., & Freneat, T. (2025). Strengthening a blue economy after habitat loss: Assessing anti-trawling structures and small-scale fisheries impacts in Cambodia’s Mission Blue Hope Spot. Frontiers in Marine Science, 12. doi:10.3389/fmars.2025.1656017
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