Experts are concerned that the diversion of water from the Salween River to the Ping River could lead to a decline in fish stocks due to competition from invasive species and genetic contamination.
Fisheries biologist at Maejo University, Apinan Suwannarak, on Sunday said the Nam Yuam Dam project -- which could divert up to 1.8 billion cubic metres of water from the Salween River basin along the Thai-Myanmar border to the Ping River, which is located further inside the country -- could threaten the survival of up to 98% of the species found along the Ping River.
"We still don't fully understand the biology and behaviour of many species in the Salween. Most of the fish found in the river migrate towards the estuary to lay eggs, so the dam might affect their chances," he said.
Invasive species introduced via the dam's channels could also alter the ecology of the basin, Mr Apinan said.
Sathan Cheevavichaipong, a coordinator for the Yuam-Ngao-Moei-Salween River People's Network, said the stretch of the Salween River which runs through Thailand is the only part of the river that hasn't been dammed.
The river has been dammed at 13 points in China, and seven points across Shan and Karen states in Myanmar, not far from the Thai-Myanmar border.
Last week, the International Union for Conservation of Nature (IUCN) and Maejo University's Faculty of Fisheries held a workshop discussing the biodiversity of the Salween River system.
Local research has identified several fish species unique to the river, including the sa-ngae fish.
Twelve villages were declared conservation areas to allow experts to carry out further study, the workshop was told.