Fish are tremendously important in Cambodia, accounting for up to 80 percent of Cambodians' protein intake. An estimated 600,000 tons (544,000 metric tons) of fish are caught in Cambodia annually.
The river's seasonal nature makes it very productive, Hogan says. During the rainy season, Tonle Sap Lake in central Cambodia expands five times, opening up new habitat and releasing nutrients. When the lake contracts in the dry season, fish are pushed out of the lake and into the river.
"On a good day, the fishermen here can almost scoop up dinner with their bare hands," said Hogan, sitting in a boat in the middle of the bustling Tonle Sap.
But Hogan sees troubling signs. While the overall catch has steadily increased over the years, the catch of large species has plummeted, mostly due to overharvesting.
"We are seeing a decline in all the large fish species," Hogan said. "When people here don't have large fish to fish anymore, they will switch to medium- and small-sized fish. But what happens when those fish disappear?"
The situation is particularly acute with the giant catfish. A hundred years ago, it was found throughout the Mekong River Basin. Historical records show that perhaps thousands of fish were caught every year.
Today the catch has dropped to between five and ten fish per year, and the fish is only captured regularly in Cambodia.
In 2000 Hogan launched the Mekong Fish Conservation Project, which has received funding from the National Geographic Society's Conservation Trust, in Thailand. It moved to Cambodia in 2001 due to the closure of Thailand's giant catfish fishery.
"Our main objective is to tag and release the endangered species that they catch here and follow them to the areas where they feed or spawn in order to piece together the ecology of the fish and learn more about their life cycle," Hogan said.
In addition to the giant catfish, the project focuses on other endangered species, such as the giant barb, the national fish of Cambodia, and the seven-striped barb.
The once-common river catfish is not yet recognized as endangered, but its numbers have also plummeted.
As a short-term measure, Hogan has purchased endangered fish from the fishers to tag and release them back into the river. The establishment of a conservation area on the Tonle Sap, he says, is a more permanent solution.
"The buy-and-release program was always the short-term solution," he said. "We can't keep buying these fish for the next hundred years."
He acknowledges, however, that there is little incentive for the fishermen to cooperate with the new plan. A giant catfish can fetch hundreds of dollars on the market, an income that some fishermen may be reluctant to give up.
To enforce the rules, the Cambodia Department of Fisheries has instituted a 24-hour monitoring program of the fisheries.
"It is critical that we do everything we can to protect these endangered species," Hogan said. "Otherwise it could be the that this year is the last year we see the giant catfish."
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