Eight endangered Mekong River dolphins have died so far this year, half the number that died in all of 2003, an expert said Sunday.
Six calves and two adult dolphins, found in southern Laos and northern Cambodia, have died in the last three months, said Isabel Beasley, a dolphin expert with the Mekong Dolphin Conservation Project. The calves died of unknown causes, but the adults were caught in nets, she said.
Record-low river water levels—the lowest in a decade—are probably at least partly responsible for the increase in mortality, she said. Low water tends to concentrate dolphins and fishermen in the same areas, causing more to be caught in nets.
But there also seems to be something else going on, she said.
“There shouldn’t be so many calves dying,” Beasley said. There were no indications that the dead calves were caught in nets, she said.
“It could be that there’s some environmental pollution, such as a chemical going into the water,” Beasley said, adding that toxic chemicals have been known to kill dolphin calves in other areas. There are two gold mines in Kratie province, she said, and it is possible that chemicals such as mercury, sometimes used in mining, are leaching into the water.
Sam Kim Lorn, director of
fisheries for Kratie province, said that water on the Mekong was black and could be polluted, though no samples have been tested yet.
Beasley said her team will send the blubber of the dead dolphins to be tested for contaminants.
“It could also be that the population has gotten too small and there is some inbreeding going on,” Beasley said.
Mekong River, or Irrawaddy, dolphins are also found in rivers in Indonesia and Burma, as well as coastal Asian waters. But the population that lives in Laos and Cambodia is considered a genetically distinct sub-population, Beasley said. It is estimated that there are fewer than 100 left in the wild, she said.
Fishing nets are the biggest threat to the endangered dolphins, Beasley said. Sometimes the dolphins are accidentally caught in large gill nets and drown, but in other cases, locals have been known to kill and eat caught dolphins rather than release them.
Sam Kim Lorn said fisheries officials have told fishermen not to use gill nets in areas where the dolphins live.
However, Beasley said, there is no law restricting the use of such nets. A fisheries law, which would control the net fisheries, is currently before the Council of Ministers, but the monthslong political deadlock has stalled its progress, Beasley said.