Men in mud-splattered rubber trousers stand in small flat boats drawn into a tight circle. They give a joyous shout, and their long poles rise and fall, slapping the icy black water in a rhythm that is a thousand years old.
This is how the Christmas season begins in the Czech Republic - with boisterous fishermen's jokes, Thermoses of hot tea, and the carp harvest.
On a rock overlooking the pond, Jan Hofbauer, one of the last proud carp barons of South Bohemia, directs the fishing operation by hand signals. His life's work, like that of his forefathers, has been to bring Christmas dinner to thousands of Czech families.
While in other parts of the world carp is considered an unclean pest or, at best, a poor-man's fish with a foul-smelling, low-quality meat, here it is the center of the Christmas feast.
"Czechs have eaten carp at Christmas for as long as history remembers," Hofbauer says, "and the way we do carp, it is delicious."
The fish is usually fried, often breaded, and the classic Christmas recipe, called carp black, is dressed up with a dark plum sauce.
Hofbauer and his crew of village men use the same techniques their ancestors have used for centuries.
First, the pond is slowly drained. Then, the men use nets and poles to round up the fish in shallow water and scoop them into baskets, where they are carefully sorted into those that can be sold this year and those that must spend another winter under the ice.
Czech scientists say that carp can survive very harsh conditions but only reach their full potential in size and flavor when given special care. While species of carp have taken over tepid waters in North America only to produce undersized and unsavory offspring, Czech carp often weigh as much as 10 pounds and have a fine, buttery taste.
The difference lies primarily in the labor-intensive methods of farmers like Hofbauer and the complex system of ponds where the fish are raised - a process that takes three to four years.
Of 23,000 man-made ponds in the Czech Republic, 95 percent of them are used to farm carp. A local fish-farming system consists of dozens of ponds interconnected by gates and channels that bring in fresh water in the spring, drain and clean the ponds in the fall, and keep fish sorted and sheltered through the winter.
"Carp have to be raised in these pond systems and fed natural cereals," says Martin Flajshans, a scientist at the Research Institute of Fish Culture and Hydrobiology in South Bohemia. "Carp raised any other way have jelly-like meat, smelling of mud and algae."
The first written record of this kind of carp farming in the Czech lands dates from the 11th century, when Roman Catholic monasteries began cultivating fish for food during Lent. It quickly developed into a closely guarded Czech trade.
Today, induction into the fisherman's guild still requires a frigid initiation, which includes an oath to serve the patron saints of fishing, a dunking in ice-cold water, and a swift spanking with an ornate wooden paddle.
In the 15th century, Stepan Netolicky designed a system of fish ponds around a 25-mile long Zlata Stoka (Golden Drain) running through Trebon, which is still a considered a small marvel of engineering.
At the time, much of South Bohemia was marshland. But slowly the landscape was changed by the fish ponds, which retain and reuse water while allowing surrounding land to be cultivated. Now, the ponds and the giant oak trees that cling to their dikes are a natural part of the Czech countryside and shelter a host of wildlife and birds.
Hofbauer's family, which owns 16 ponds in the Trebon area, began trading carp to Vienna in exchange for wine in the 16th century.
The farm compound, with rough stone walls, a windmill, and an interior courtyard sheltering the huts of farm workers, still has the look of a medieval fort. Indeed, it once had a moat, built on carp wealth.
But in 1949, when the Communist Party took over what was then Czechoslovakia, the Hofbauers' prestige became a liability. As the wealthiest farmers in the area, the family was stripped of land and forced to work at menial jobs. Hofbauer, who was 25 at the time, was banned from the fishing industry altogether, while his father was imprisoned for five years.
"Fishing was everything to me as a boy," Hofbauer says, as he clenches his fists. "It was extremely painful for me to be banned from fishing. I missed the ponds terribly."
The Velvet Revolution of 1989 turned the tables again and Hofbauer was able to return to his childhood home. The buildings were crumbling, and the winter holding ponds had been destroyed. "I am still rebuilding," he says. "But I just had to come back. I could not just let go of such a strong tradition which had been built by so many generations. I couldn't live with myself if I did."
Of the 620 farming families in the area, only seven have gone back to agriculture since the Velvet Revolution. Now, in a region where every village once had two or three fish farms, Hofbauer's is the only profitable family operation left.
Today Hofbauer produces 110,000 pounds of carp yearly and sells it at around 60 cents a pound. That is enough to compete with big farming companies, and Hofbauer now expects that his grandson, also named Jan, who at 19 is studying at a fishery academy, will return and take over the farming operation from him.
"That makes me a happy man," he says, with a broad grin. "This is one family tradition that isn't going to die."
As for this Christmas, when asked if she is too tired of working the carp ponds to cook the fish, Hofbauer's wife Hana laughs.
"We have to have carp for dinner," she says. "It wouldn't be Christmas without carp."