A genetic study of blackchin tilapia populations in Thailand has found high levels of genetic diversity among the…

DNA can't pin down source of spead

PUBLISHED : 22 Jun 2026 at 04:47

A genetic study of blackchin tilapia populations in Thailand has found high levels of genetic diversity among the invasive fish, but the DNA evidence could not determine how the species entered or spread across the country.

The study, led by Porntep Punnarak of the Aquatic Resources Research Institute, analysed 466 specimens collected from 20 locations nationwide to examine the species' genetic structure across Thailand.

The study identified 19 distinct genetic haplotypes among blackchin tilapia populations, indicating a relatively high level of genetic diversity.

Some haplotypes were widely distributed across multiple regions, while others appeared restricted to specific localities.

The team also found contrasting patterns in genetic structure, with some nearby populations showing marked differences while some distant populations shared similar genetic traits.

Researchers said such patterns could result from multiple factors, including natural dispersal, human-mediated movement and mixing between populations from different sources.

In addition, the samples showed genetic similarities with reference populations from West Africa, particularly Ghana and Côte d'Ivoire.

However, the research team cautioned that genetic evidence alone cannot determine the precise pathways through which the species spread across Thailand.

Mr Porntep said DNA is a useful tool for studying genetic relationships, levels of diversity and geographic distribution patterns among populations, but it has limitations when used to interpret human activity or specific historical events.

"DNA cannot identify who imported the fish, when it was released into the wild or whether it escaped from aquaculture systems," he said.

Such questions require additional evidence, including import-export records, farming histories, field surveys and official documentation.

The main value of DNA analysis lies in helping authorities understand population structure and genetic variation within Thailand's blackchin tilapia populations, he said. Such knowledge can support long-term monitoring, inform management strategies and improve efforts to control the spread of invasive species across aquatic ecosystems in the country.