This undated photo provided by Chhut Chheana shows a researcher holding a giant salmon carp Aaptosyax grypus rediscovered in Cambodia. (Chhut Chheana/Wonders of the Mekong via AP)

This undated photo provided by Chhut Chheana shows a researcher working on a giant salmon carp Aaptosyax grypus rediscovered in Cambodia. (Chhut Chheana/Wonders of the Mekong via AP)

This undated photo provided by Chhut Chheana shows a giant salmon carp, rediscovered in Cambodia. (Chhut Chheana/Wonders of the Mekong via AP)