Why snakes are disappearing from Southeast Asia’s largest lake
KRAKOR, CAMBODIAHer name is Den Yam, but people know her as the “snake lady.”
We’ve come to the floating village where Yam, 48, lives deep inside the flooded forest surrounding Cambodia’s Tonle Sap Lake, to talk to her about the world’s largest snake hunt.
Sitting on a wooden floor in front of a wall lined with gold-framed portraits of Cambodian royalty, Yam warmly receives our group of fish experts. She explains that area fishermen come to sell her aquatic snakes—“the one with the white belly,” “the one that eats frogs,” and so on—which she then prepares for sale. The skins are boiled and used to feed fish many people keep in their houses to sell or use as food for their families.
Yam dries, seasons, and packs the snake meat into strips for grilling or frying. “It’s very good with beer,” she says with a chuckle.
Most of her snake products are sold wholesale at the local market in Krakor, at the western end of Tonle Sap. A kilo (just over two pounds) of processed meat, which requires some 50 snakes, goes for about 50,000 riel, or $12.50.
Tonle Sap, which was designated a UNESCO Biosphere Reserve in 1997, is Southeast Asia’s largest lake and an ecological wonder. After the annual monsoon rains begin, around June, it can expand by up to six times, shrinking again during the dry season. This flood-pulse system works like a beating heart, filling and emptying the lake through its eponymous river, a major tributary of the Mekong River.
Tonle Sap is of immense commercial importance. At least 500,000 tons of fish are drawn from it each year—more than from all of North America’s rivers and lakes combined—feeding millions of Cambodians. (Learn more: Mekong river fish feed millions, but is it sustainable?)
As astonishing as this harvest is, says Zeb Hogan, a biologist from the University of Nevada, Reno, and a National Geographic Explorer, the lake is nowhere nearly as bountiful today as it was just a couple of decades ago. Stocks then were so abundant, he says, that you could dip a bowl in the water and come up with enough food for dinner.
Hogan, who has worked in the region for 20 years and leads a USAID research project called Wonders of the Mekong, says fishing pressure in Tonle Sap is wiping out populations of large- and medium-size fish. “The most vulnerable animals, like the Mekong giant catfish, the current record-holder for largest freshwater fish on Earth, are almost gone,” he says. (Read: Critically endangered giant fish of the Mekong on the menu.)
It was in the late 1990s that fishermen, faced with declining yields of other, more valuable species, began catching snakes to sell to businesses that raise crocodiles for their skins. According to a study in 2000, tens of thousands of fishermen collected some seven million water snakes from Tonle Sap each year during flood season. That’s when the snakes, which aren’t venomous, move into new habitats in the lake and are easiest to catch.
The 2000 study described this haul as the “greatest exploitation of any single snake assemblage” in the world. (Snake hunting—for food and for traditional medicines, leather, and other products—is also widespread in countries like Japan, Vietnam, and Thailand, and snake farming in Asia has been increasing during the past decade.)
Fishing for water snakes in Tonle Sap is legal, even though some species are listed as threatened by the International Union for Conservation of Nature (IUCN), which sets the conservation status of animals.
In 2012, the Cambodian government dissolved the system of commercial fishing lots that had been in place since colonial times, opening up the entire lake to community fishing. By then croc farms had generally switched to even cheaper feed than snake meat, such as farmed fish from Thailand. But subsistence fishermen, who are among Cambodia’s poorest people, continue to catch water snakes in gill nets and trap nets, selling them for human consumption. Some snakes are exported to Vietnam and China, but most are eaten locally in Cambodia, where a pregnant female is considered a special delicacy.
Den Yam is worried: In her estimation overfishing has reduced the snake catch on the west side of the lake, where she lives, by as much as 30 to 40 percent during the past 5 to 10 years.
“I don’t know if there will be any snakes left in future,” she says.
No one knows what bad things will happen if the water snakes disappear. “Water snakes play a crucial role in Tonle Sap,” says Simon Mahood, an ecologist with the nonprofit Wildlife Conservation Society office in Cambodia. They provide “food for threatened birds, such as adjutant storks, which the flooded forest is extremely important for, and as predators of frogs and small fish.”
WHAT’S IN HORM SOK’S NET?
It’s close to noon as we slalom between the tops of trees poking out of monsoon-swollen Tonle Sap in Horm Sok’s longtail boat. Along with Hogan, our group includes Peng Bun Ngor, a fish ecologist with the Cambodian Fisheries Administration, and Thach Phanara, the head of laboratories with Cambodia’s Inland Fisheries Research and Development Institute. Sok, 56, is taking us out to check on one of his trap nets. Floating atop a submerged tropical forest is a peculiar feeling, as if nature itself has been upended.
Sok has been a subsistence fisherman on the lake for two decades. At first, water snakes were so plentiful that they were among his main targets, but nowadays he, like most other fishermen, considers them bycatch.
We’ve been going about 20 minutes when the vegetation becomes so dense that Sok is forced to cut the motor and paddle. We hear the flapping wings of a cormorant as we glide into the clearing where his trap net is set. Two teenage boys who work with him are already there. One of them dives into the muddy waters to untie the net from the bottom, apparently unfazed by the possible presence of pythons (although pythons are much rarer now in Tonle Sap).
Sok empties the net’s contents into the boat. The catch is relatively small but very varied, which is to be expected because Tonle Sap is one of the most biodiverse water bodies on Earth.
“The biodiversity hidden in these murky waters can be difficult to appreciate until you see it concentrated in a fishing trap,” Hogan says, sifting through the catch. He counts more than 20 species, including several catfishes, gouramis (also known as kissing fish), climbing perches, two different species of snakehead, a small pufferfish, even a snail-eating turtle.
Slithering at the bottom are two slim brown snakes about two feet long. A black zigzag pattern on top confirms that they’re longhead water snakes, a species endemic to Tonle Sap and listed by the IUCN as “vulnerable.”
“In the past,” Sok says ruefully, “I could catch even 10 kilos [22 pounds] of snakes in a day.” That would amount to dozens of snakes. “Now it’s mostly like this.”
It’s not just the number of snakes in Tonle Sap that’s been declining; it’s also their age and size. Like most of the fish in Sok’s net, the longheads are juveniles. This isn’t surprising to Ngor. “It’s what happens when people fish down the food web,” he says.
After depleting large, high-value fish such as catfishes, sheatfishes, and snakeheads, which are especially vulnerable to the kind of indiscriminate fishing occurring in Tonle Sap, fishermen look for species, such as water snakes, that are lower down the food chain.
“Initially,” Hogan says, “this shift to fishing down the food web can lead to increasing or seemingly stable total catch.” In other words, catches of the new, less prized species will make up for, or exceed, diminishing catches of the more desirable ones. But eventually, he says, “all aquatic resources, one by one, are depleted.”
Clearly, water snake populations in Tonle Sap are shrinking. Fishermen working on the north and east side of the lake corroborate Den Yam’s grim estimate of declines on the western side. The snakes’ fate hasn’t been helped by forest fires around the lake during a recent dry season that likely destroyed much of their habitat.
We see one sign that fishing in Tonle Sap has reached the low end of the food web—people harvesting mollusks. Sok himself has started collecting snails, which are easy to scoop from the surface of the water. Later, at his floating house, we see two five-gallon sacks of apple snails, so named because of their round shape and large size.
Other fishermen are going after clams, raking them up from the bottom of the lake, which can disturb animals such as worms that burrow in the sediment and can puncture non-target shellfish. It’s a worrying development, Ngor says, because mollusks, like reptiles, crustaceans, and amphibians all play vital roles in the rich Tonle Sap ecosystem.
THE ENFORCEMENT CHALLENGE
The Cambodian government has put restrictions on how, when, and where snakes—and all other animals—can be taken from Tonle Sap, and fishing laws prohibit the use of certain gear. Furthermore, large-scale fishing is banned from June 1 to September 30, although subsistence fishing is allowed during those months. And some parts of the lake have been designated as conservation zones where fishing is outlawed.
“This helps to a certain extent,” Pen Bun Ngor says.
Nevertheless, during our time with Horm Sok we saw illegal nets being used and conservation boundaries being ignored. Several fishermen, who asked not to be named for their protection, told us that paying bribes to law enforcement officers is common.
Enforcing the fishing rules is difficult, Ngor says, because there’s a “lack of human and financial support from the government.” The ever-changing shape of the lake adds to the difficulties of policing it.
As Ngor points out, people who have always depended on fishing the lake for a living have no other way to put food on the table. “It’s hard to think about things like fishing down the food web, and the problems it brings, when your stomach is empty.”
Near the end of our outing with Horm Sok, we put in at a floating village where we meet some snake dealers who sell us seven or eight live water snakes in a burlap bag. Among them are a Jack’s water snake, named after Merel “Jack” Cox for his years of dedication to the study of snakes in Thailand, as well as the rarely collected Boucourt’s snake, a popular menu item in China.
Heading about half a mile out into the lake, we release the snakes in a spot secluded by foliage. Even so, given the number of trap nets in the vicinity, we imagine it will be only a matter of time before these snakes are caught again.
Stefan Lovgren is a journalist, author, and filmmaker who covers wildlife and environmental issues, primarily in Africa and Asia. Follow him on Twitter.