High genetic structure between natural populations of bighead catfish Clarias macrocephalus (Günther, 1864) from the Mekong Delta and Peninsular Malaysia

•Genetic diversity of wild Clarias macrocephalus populations were higher in the Mekong Delta than in Peninsular Malaysia.•No evidence of recent bottleneck events among all populations suggesting the wild populations were at healthy conditions at present.•Translocation of the catfish could have occurred as evidenced by movement of immigrants from the Mekong Delta to Peninsular Malaysia.•Deviation from HWE and homozygous excess in Peninsular Malaysia populations could be consequence of inbreeding.