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From pest to plate: How Thailand's fish farms battle the blackchin tilapia invasion

Once thriving aquaculture businesses across Thailand’s coastal provinces have been upended by a tiny fish. Photo: Peerapon Boonyakiat/HaRDstories

Thailand is grappling with the spread of the invasive blackchin tilapia, a fish species originating from Western Africa. In the affected coastal areas, locals are crafting a pungent, yet innovative solution.

The morning sun glinted off the sea bass as Jittagon Buadee’s knife sliced through their glistening flesh. In the ponds behind his home, the 42-year-old fish farmer had just pulled in what should have been a decent haul. But his once thriving aquaculture business, like many others across Thailand’s coastal provinces, had been upended – by a tiny terror.

The blackchin tilapia seemed innocuous at first – a little fish from Africa, accidentally released over a decade ago into the country’s warm coastal waters. But in the years since, this invasive species has colonised the region’s estuaries and fish farms at a frightening pace. Forming dense, ravenous shoals, these small predators have perpetrated devastating attacks on native aquatic young.

“Previously, I could earn up to one million baht annually,” said Jittagon, who was forced to switch from shrimp farming to raising sea bass. “Now my income is just 200,000 to 300,000 baht per year (5,400 – 8,100 USD).” All around his village are abandoned aquaculture ponds, the owners put out of business by the blackchin tilapia’s appearance.

Thailand, one of the world’s top processed seafood exporters, relies heavily on its coastal aquaculture. But parts of that multi-billion dollar supply chain are now menaced by the invading fish contaminating the warm brackish estuaries on which it depends.

An industry at risk

Located along the deltas where five major rivers flow into the Bay of Bangkok, the coastal provinces of Phetchaburi, Samut Songkhram, Samut Sakhon, and Samut Prakan have long been the heart of Thailand’s seafood production. 

This region, blessed with rich biodiversity and abundant aquatic resources, has contributed to making the country the world’s eighth-largest exporter of processed seafood by volume and 14th by value, according to Krungsri Research. It hosts many of the over 10,000 registered operations that supply the bulk of the raw materials for this global seafood powerhouse.

However, local fish farmers fear for their future as the blackchin tilapia severely impacts the aquaculture sector.

“My family is faring better than most of our fellow fish farmers,” said Jittagon, who owns two ponds in Phetchaburi’s Khao Yoi District. “Many smallholder aquaculture farmers and traditional fishermen are suffering severe losses and are on the brink of collapse due to the devastating consequences of the blackchin tilapia invasion.”

A native of West Africa, a scourge in Thailand

The blackchin tilapia (Sarotherodon melanotheron), a medium-sized fish from the Cichlidae family, is native to the brackish coastal ecosystems of West Africa. Living in large schools, these carnivorous fish feed on the juveniles of other aquatic species. 

Thailand’s Department of Fisheries considers them one of the most devastating invasive species due to their resilience, rapid reproduction, and ability to decimate native fish populations.

Blackchin tilapia’s tolerance for high salinity allows them to spread along coastlines and invade new areas. They are already classified as invasive in Florida, Hawaii, and the Philippines, according to the Global Biodiversity Information Facility’s database.

The invasion begins

​​According to the Fisheries Department, blackchin tilapia’s introduction to Thailand can be traced back to 2010, when a large food company imported them as experimental subjects to improve their commercial fish breeds. Despite the company’s claims of exterminating all the imported fish after the experiment failed, people in Samut Songkhram’s Amphawa District began noticing blackchin tilapia in the wild in 2012, marking the likely beginning of the invasion.

Since then, verified sightings of blackchin tilapia have been reported in 13 provinces along the Gulf of Thailand’s coastline, from Chantaburi in the east to Songkhla in the south, ThaiPBS’s reported last year.

Chavalit Vidthayanon, a senior aquatic ecology specialist at the Mekong River Commission, warned that blackchin tilapia pose a grave threat to the region’s aquatic ecosystems and biodiversity. These invasive fish have completely taken over some ecosystems, leading to a steep decline in both the population and diversity of native fish and other aquatic species.

“Blackchin tilapia rapidly expanded from a handful of escaped fish in Samut Songkhram to infest the entire coastal areas throughout the Gulf of Thailand in just a few years,” Chavalit told HaRDstories.

He warned that without systematic eradication of this alien species, blackchin tilapia could invade Singapore and the Mekong River Delta within the next five years, further exacerbating the ecological crisis.

Fish farmers left with few options

The aquaculture sector has been badly hit by the invasive fish. Blackchin tilapia can easily enter fish farms through water diversion channels when ponds are refilled from nearby natural waterways. Once inside, they rapidly reproduce and consume the cultivated fish, eventually overrunning the entire farm.

“Fish farmers have few options: switch to sea bass, which prey on blackchin tilapia; bear higher costs to upgrade their farms; or go out of business,” Jittagon said.

The problem is made worse by the fact that blackchin tilapia are small and have little meat, making them undesirable for human consumption. As a result, they are usually sold as bycatch for a mere four baht per kilogram. 

In contrast, the snakeskin gourami, a commercially important native Thai fish of similar size, can fetch prices ranging from 160 to 350 baht per kilogram.

A pungent solution

Despite the decade-long invasion, Jittagon noted that few official measures have been taken to address the problem, leaving affected communities to fend for themselves.

Faced with rivers and canals teeming with tiny, inedible blackchin tilapia, Jittagon and his fellow fishermen have been forced to find creative solutions. “We need to find a way to get rid of these numerous tiny fish as efficiently as possible,” he said. “So I came up with the idea to add more value to these unwanted fish by fermenting them into fish sauce.”

Inspired by childhood memories of his parents brewing their own fish sauce from anchovies, Jittagon realised that many coastal communities have their own family recipes for this classic condiment. “Nowadays, we no longer make fish sauce at home due to the intense odour from fermentation,” he explained. “It’s just easier to buy it at a nearby supermarket.”

To adapt his family’s recipe for blackchin tilapia and tackle the smell problem, Jittagon made some alterations and improvements. The result, he believes, is very satisfying. “The fish sauce from blackchin tilapia turns out great! The taste is even better than the original anchovy version, and the tight plastic sealing of the fermented jars greatly reduces foul odours.”

Jittagon’s fish sauce quickly gained popularity online, with his first batch selling out within days. ‘This solution could be widely adopted to tackle the blackchin tilapia invasion and help affected communities earn income from this alien fish,’ he said.

However, just as Jittagon’s initiative was gaining momentum, he was forced to temporarily halt production. The local Public Health Office warned him that his fish sauce did not meet required regulations and food safety standards, making it illegal for him to continue producing and selling the product online.

Government’s lacklustre response

Jittagon, while complying with the suspension order and pursuing legal avenues to produce and sell his fish sauce, remains disillusioned with the authorities’ handling of the blackchin tilapia crisis. “The official measures were too little, too late to contain the spread,” he laments. “The government also failed to provide assistance and relief to help affected communities.”

Despite his disappointment, Jittagon believes local communities, authorities, and stakeholders must collaborate to address the problem, urging official agencies to amend laws and regulations to incentivise the catch and use of blackchin tilapia.

Meanwhile, Bancha Sukkaew, director-general of the Department of Fisheries, announced new measures to control the invasive fish, including releasing native carnivorous sea bass and permitting limited use of intensive fishing equipment. 

“The Ministry acknowledges the hardships faced by fishermen and fish farmers and is committed to stopping the alien species’ spread,” Bancha told HaRDstories.

The Fisheries Department’s plan involves releasing 60,000 sea bass and deploying 23 fishing vessels with push nets in five pilot provinces, while collaborating with stakeholders and local communities to raise awareness and encourage public involvement.

However, affected communities remain sceptical of these efforts. Panya Toakthong, a representative from Samut Songkhram, believes the authorities fail to grasp the severity and complexity of the situation, resulting in inadequate plans. 

“It’s too late to stop the invasion by using push nets and introducing sea bass, as the fish have already spread beyond control,” Panya warned, adding that these measures could inadvertently harm native aquatic species.

A call for inclusive collaboration

Given the near impossibility of containing and eliminating blackchin tilapia in the wild, Panya believes a shift in strategy is necessary. He urged authorities to support and empower local communities, enabling them to adapt to an environment now dominated by the invasive species.

“Instead of solely focusing on control and eradication, authorities and stakeholders should work closely with local people to find ways to transform blackchin tilapia into marketable products,” Panya suggested. This approach, he argued, could provide additional income for communities while helping to control the fish population through increased catch and utilisation.

He also called on the Department of Fisheries to invest in researching scientific solutions that directly control the reproduction of the invasive fish without harming other species.

“As the local inhabitants who live with and are directly exposed to the problem, they know the real situation and understand the nature of their locality the most,” Panya said. “It is time for official agencies to listen to the people, work with them, and support them to ensure constructive solutions that truly match the needs and interests of local communities.”

Pratch Rujivanarom writes about environmental justice and human rights in Thailand and Asean. After graduating with a Master’s degree in International Journalism from Birmingham City University, he started his career as an environmental reporter at The Nation newspaper in 2015. 

Peerapon Boonyakiat is a freelance photojournalist based in Bangkok and working for Hong Kong-based SOPA Images. He is interested in political stories involving conflict between the people and the government. 

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