Fishermen who have lived off the Tonle Sap river in Phnom Penh’s Russey Keo district for generations were forced upstream recently after hundreds of dead fish mysteriously appeared in local waters.

The 29 families who live on houseboats from which they cast their traps started moving to Kandal province’s Lvea Em district on June 1, said Chea Thol, the district’s police chief. The small floating village’s move to the district’s harbour is temporary, he said. It is currently unclear what is causing the fish to turn up dead, he added.

“Some of the fishermen said water in the location in Russey Keo district, where they caught fish, seems contaminated or lacking oxygen, leading 300 to 500 fish to die each day,” Thol said. “They have decided to move here temporarily to catch fish that are not in [possibly] polluted water.”

Ten families made the eight-kilometre move up the current on June 1, followed by another 19 on Saturday, Thol said. Some families had fished in the Russey Keo location since the fall of the Khmer Rouge.

A sudden skyrocketing of fish deaths in the area has evoked suspicion that industrial factories in Russey Keo district are the cause, Tim Seleh, a representative of the families, said.

“We suspect that some factories are secretly dumping their poisonous waste into the river,” Seleh said yesterday. “[Poison] flowing into the water current this month is killing our fish all the time.”

In a day, more than a tonne of fish there died, a loss that cost Seleh millions of riel, he said. Seleh and other affected families are calling for local fisheries experts to survey the area to find out what’s causing the fish to die in such large numbers.

Russey Keo district Deputy Governor Ly Rozamie said shallow water and hot temperatures are likely depleting the water of oxygen and suffocating the fish.

“However, we would like to ask environmental and fishery experts to examine the water to find the cause,” Rozamie said.