It has been described as the “most invasive species” Thailand has ever seen, with the potential to cause huge damage to the environment, officials said.
To control it, people waded into the lake and genetically modified it.
However, black gold tilapia is still spreading in Thailand’s waterways, affecting 17 provinces so far.
“We will not pass on damaged ecosystems to the next generation,” Bangkok MP Nattacha Boonchaiinsawat declared during a parliamentary inquiry aimed at finding out the causes and their supporters.
So, can the Thai authorities win this battle?
There have been outbreaks of black-jawed tilapia in Thailand in the past, but none were as widespread as the recent incident.
Mr Nattacha estimates that this particular outbreak will cost the Thai economy at least 10 billion baht ($293 million; £223 million).
The core problem is that black-cheeked tilapia prey on small fish, shrimp and snail larvae, which are important aquaculture products in Thailand.
So for months the government has been encouraging people to catch black-jawed tilapia, a fish found in rivers and swamps. This fish thrives in salt water but can survive in both fresh and salt water.
The Thai government has also doubled the amount it pays fishermen to 15 baht ($0.42; £0.33) per kilogram. The result? On the outskirts of Bangkok, people waded into knee-deep waters hoping to catch black-cheeked tilapia in plastic pots.
Authorities have also released the blackcheek tilapia’s natural predators — Asian bass and long-whiskered catfish — to hunt them down.
However, they are battling a species that reproduces extremely quickly: females can give birth to 500 fingerlings at a time.
Therefore, the authorities have also begun to develop genetically modified black-cheeked tilapia to produce infertile offspring, and plan to release it as early as the end of this year in order to prevent its population from further increasing.
But Mr Natacha told BBC Thai the government needed to do more.
“Who will win?” he wondered. “We need people to keep an eye on the cases, otherwise this will go unnoticed and we will pass this environment on to the next generation.”
So how did this fish – easily identifiable by its dark spots on its chin and cheeks – end up in Thailand?
One theory being investigated by parliament is that an experiment 14 years ago by food giant Charoen Pokphand Foods (CPF) led to the spread.
The company produces animal feed and operates shrimp and livestock farms, importing 2,000 fish from Ghana in late 2010.
Two years later, a black-spine tilapia outbreak occurred in Thailand, including in the CPF laboratory area, according to Thai PBS.
But CPF, an agricultural business owned by Charoen Pokphand Group (CP Group), one of Thailand’s largest conglomerates, has denied the accusations. It also threatened to prosecute those who spread what it called “misinformation” on the matter.
It is working with national agencies to combat the spread of alien species.
CPF aquaculture and research and development officer Premsak Wanuchsoontorn said, “Although the company is convinced that it is not the cause of the outbreak, it is not indifferent and is ready to cooperate with the government to alleviate the suffering of the people.”
However, CPF officials have only attended one parliamentary hearing in person. They had previously given written explanations to lawmakers.
Bancha Sukkaew, director-general of Thailand’s Fisheries Ministry, noted that only one private company has sought permission to import black Chin tilapia.
He told the BBC it was possible some people had escaped from the laboratory.
However, he did not rule out the possibility of invasive fish being smuggled into Thailand.
But ultimately, how they got into Thailand’s waterways is a thing of the past, and the question is the future, and how to contain the outbreak. But is this possible?
The battle against blackcheek tilapia may be lost, experts told BBC Thai.
“I don’t think it’s possible to eradicate it,” said Dr. Suwit Wuthisuthimethavee, an expert in aquatic animal genetics at Valerac University.
“Because we can’t limit its range. When it’s in nature, it keeps reproducing and the reproduction cycle is very fast,” Dr. Suwit added.
Freshwater ecology expert Nonn Panitvong agrees.
“The problem with exotic species is that once they become established, they are very difficult to eradicate,” he said.
