Voracious invasive fish devastates Thai waters and livelihoods

A fast-breeding invasive fish is wreaking havoc across Thailand, wiping out shrimp stocks, threatening native wildlife and leaving fishing communities struggling as experts warn the battle to contain it has already been lost.

Blackchin tilapia, a species native to West Africa, has spread across at least 19 Thai provinces since it was first detected in 2011. Scientists now believe eradication is no longer realistic, shifting the focus to limiting the damage.

Shrimp Farms Left Empty

For shrimp farmer Wallop Khunjaen, the invasion was devastating. Within weeks, millions of juvenile shrimp disappeared from his ponds as blackchin tilapia consumed almost everything in their path.

"They ate the shrimp, they even ate the crab," he said, describing how native species have become increasingly scarce. The losses forced him to abandon shrimp farming altogether.

Authorities Race to Slow the Spread

Thai officials have launched a series of countermeasures, including releasing predatory Asian sea bass, developing sterile strains of blackchin tilapia and paying fishers to remove the species from waterways.

Thousands of tonnes have been caught, but researchers say the fish's rapid reproduction and ability to thrive in both freshwater and brackish environments mean populations quickly recover after removal.

Turning a Pest Into a Product

Scientists increasingly argue the most practical solution is to create commercial demand for the fish. Blackchin tilapia is already being processed into animal feed and fermented fish products, while some restaurants have begun adding it to menus.

Yet convincing consumers remains difficult. Traders say demand is weak despite the abundance of fish, leaving communities with huge catches that generate little income.

Questions Remain Over the Origin

The source of the invasion remains disputed. Fishers have filed legal action against agribusiness giant Charoen Pokphand Foods, alleging the company introduced the species after importing blackchin tilapia for breeding research in 2010.

The company rejects the allegation, saying all imported fish were destroyed under controlled conditions and citing research suggesting the invasion was not caused by a single release.

As the fish continues spreading through Thailand's rivers, canals and coastal waters, scientists warn the ecological consequences could last for decades. For many communities already living with the invasion, the concern is no longer whether it can be stopped, but how much more damage lies ahead.

‘They ate the shrimp, they even ate the crab’: Thai fishers count the cost of a voracious invader