A soup tureen and two aromatic platters of unrecognizable food steamed on the table in front of me. My companions chatted happily in Khmer and began loading their plates. I peered closer and began to discern forms. On one platter were some tiny freshwater crabs that had been diced, fried, and stewed in spices. On another I saw the bald head and beak of a chicken peeking out from under a chopped pile of its own organs and body parts. Perched on one side was a rubbery brown disk. In the tureen bobbed chunks of flaky white fish and a complete set of cooked fish innards. The smells were tantalizing—chilis, garlic, lemongrass, and prahok, a fermented fish paste. I braced myself and tried it all.
It was delicious, even the rubbery puck of boiled chicken blood. The only disappointment was the chicken meat, which was stringy and tough. The hens pecking nervously around us certainly looked rangy and well exercised. During the meal one whizzed past running for its life, hotly pursued by the cook, who had just received another lunch order. It was a beautiful venue and, like nearly everything in Cambodia, outdoors. We sat cross-legged on the swept wood floor of a raised open-air platform, about ten feet square and shaded by a thatched roof. Scattered around us were other shaded platforms and customers. Before us glistened an emerald pond ringed with lush vegetation. It was spanned by a rickety bamboo footbridge, to which four hand-hewn log dugouts were hitched. The water’s glassy surface dimpled and swirled with fish.
The delicate chunks of white meat came from an evil-looking creature called a snakehead. Snakeheads are a class of predatory freshwater fish native to Asia, Malaysia, Indonesia, and tropical Africa. Hours earlier, this particular individual had been yanked from the mud of a drained farm pond and handed to us as a present. It had a muscular, eel-like body with spots like a leopard, a massive head, and a gaping mouth bristling with teeth. It was fearsome to behold, yet, I was assured, delicious. We dropped it off, writhing in a plastic bag, at the restaurant to be cooked for our lunch. Snakeheads are aggressive hunters of fish, snakes, frogs, birds, other snakeheads, and pretty much anything else they can grab. They survive droughts by burrowing into the mud, as frogs do. They can breathe when out of water and squirm overland to find another stream, river, or pond. I knew horror stories about this fish from North America, where it is a rapidly spreading invasive species due to illegal introductions into the wild. Fish and wildlife managers are petrified by their voracity and resilience. Anglers call them “Frankenfish” and dread their arrival in a favorite fishing hole. I had lectured gravely about snakeheads—and other invasive species like the zebra mussel, brown tree snake, water hyacinth, and Norway rat—to students in my environmental science courses at UCLA.
In 2002, a bewildered fisherman pulled the first reported snakehead in the United States from a pond behind a Maryland strip mall. The discovery prompted a media scrum and the pond’s drainage, revealing dozens of snakehead young. They were traced back to a pair of live specimens that someone had purchased in an Asian fish market and released into the pond. Two years later, another snakehead was caught in the Potomac River, an important tributary of the Chesapeake Bay watershed. By 2018, the fish had spread upstream throughout Maryland and was colonizing nearly three new sub-watersheds per year. At this pace, snakeheads will populate the entire watershed within fifty years, including the Susquehanna, Rappahannock, James, and York Rivers.
It was disorienting to see the same creature that is so reviled in my own country prized as a high-value delicacy in another. In the street markets of Phnom Penh, I saw metal tubs full of live snakeheads that were under fierce negotiation and commanding top dollar from urban consumers. I had known all about the fish’s ecological horrors as an invasive species but had no idea it was viewed so favorably at home.
The snakehead we ate was particularly tasty and valuable because of where it came from. It was captured alive at the bottom of a deliberately drained pond and had grown up swimming and feeding in the vast fertile rice fields surrounding it. The fields were dry when I visited in December, but from May through July, during the monsoon rains, they fill with rising floodwaters from surrounding streams, rivers, and Tonle Sap Lake. During this annual submergence the artificially dug pond lies at the bottom of a vast, shallow wetland less than a meter deep. Adult breeder fish trapped in the pond during the dry season become liberated, swimming long distances through the surrounding rice fields to gorge and lay eggs. Wild fish escaping from the nearby streams do the same. The flooded rice fields explode with planktonic life, providing a rich food base for a short-lived, high-quality freshwater fishery.
Rice-field fish grow fast, reaching eating size in a matter of weeks. Their defecations settle on the bottom, providing free fertilizer to the paddies. When the monsoon rains end, the floodwaters retreat back into the streams, rivers, and artificially deepened catch ponds dug into the fields. The fish have no choice but to follow, and many get trapped in the ponds. By fall, the fields are dry, the rice is tall, and the ponds are packed with catfish, snakeheads, and other marketable fish, naturally funneled from the surrounding areas.
By merging natural seasonal flooding with low-intensity aquaculture, rice fields can become highly productive fisheries. The main requirement is digging some deep, strategically positioned ponds to trap and hold fish through the dry season. Shallow ditches radiating out into the fields maximize the ability of fish to disperse when water levels rise and be captured when levels fall. Some ponds are drained or netted, providing food and cash to the farmers. Others are protected from fishing, to maintain some brood stock. These sanctuaries, called “community fish refuges,” serve to repopulate the fields with a new generation of fish the following year.
Had our big snakehead swum into the scenic green community fish refuge next to the restaurant, it would have lived another year. Instead, it got caught in a harvest pond, which was drained. The water was pumped out into the surrounding dry rice fields to irrigate them, and two hundred kilograms of fish were plucked from the mud, dropped into live-wells, and hauled off to market to be sold for $1.50 to $2.00 per kilogram. Due to its life on a rice-field, our large snakehead, with its unusually clean taste and minimal exposure to chemicals, would have brought $10 in Phnom Penh, roughly twice the price of one raised on a conventional fish farm.
This hybrid form of aquaculture, in which natural and artificial processes collaborate, is called rice field fisheries (RFF). RFF is an increasingly popular form of sustainable fishery being promoted by governmental and nongovernmental organizations in Southeast Asia. I visited Cambodia to visit some RFF projects of WorldFish, an international, nonprofit research NGO that seeks to reduce developing world hunger and poverty through sustainable fishing.
WorldFish organizers travel to rural villages to educate farmers about how they can grow protein alongside rice in their fields. Since most villages lack the financial resources to design and build an RFF system, the NGO approaches donors and governments for grants to fund them. The cost is quite low—with necessary excavations typically costing a few tens of thousands of dollars—and mostly up front, making it attractive to foundations and donors.
One RFF project I visited was constructed in 2015 for the village of Korn Thnot, near Tonle Sap Lake. I was struck by how much its single, 200‑by‑500-foot community fish refuge pond, together with some surrounding catch ponds, was helping the villagers. As people cast nets into the catch ponds for their dinner, a Cham elder explained how not only his own village, but also surrounding villages were benefiting from the annual dispersal of fish into their paddies.
This idea of pairing aquaculture with rice farming is an ancient one. In China it was once common to rotate carp into flooded paddies, and other variants of rice field aquaculture have been developed and forgotten through the ages. Today, the concept is attracting new interest because it offers a straightforward way to improve the nutritional and financial resilience of the rural poor. More than a billion people in developing countries derive most of their animal protein from fish, and a quarter-million depend on fishing and aquaculture for their livelihoods. Through education, fundraising, and with heavy earth-moving equipment, WorldFish and other sustainable-aquaculture NGOs are cleverly pairing seasonal flood cycles with agriculture to help some of the world’s most impoverished people.
Reprinted with permission from Rivers of Power by Dr. Laurence Smith, copyright © 2020. Published by Little, Brown Spark, an imprint of Little, Brown Books.