Two veteran shrimp farmers in Samut Sakhon province have expressed doubts that the Fisheries Department’s plan to release Asian seabass into natural watercourse, to eliminate Blackchin tilapia fry, will work, because they have tried this method before without success.
Wallop Khunjeng, a shrimp farmer with 17 years of experience in Praek Nam Daeng sub-district of Amphawa district, told the media that he originally raised shrimp on his 40-hectare farm but, in 2011, when Blackchin tilapia were detected, he released about five thousand 4-5-inch seabass into a 3.2 hectare pond, in the hope that the fish would eat the non-indigenous species from Africa.
Weeks later, he said he found only about 1,000 seabass had survived, but he managed to catch about nine tonnes of Blackchin tilapia fish.
He tried again in another, larger pond and the result was the same. Then he tried, for a third time, in a smaller pond, of about 1.6 hectares, but allowed the pond to dry out before water from a canal was used to refill it.
Two weeks later, he found Blackchin tilapia fry thriving in the pond and he released a thousand 4-inch seabass into it. After a few weeks, he managed to catch about seven tonnes of Blackchin tilapia.
Then he released 1,000 8-inch seabass into the pond again and found the number of Blackchin tilapia fish dropped, only to increase again about six months later, even though the number of seabass remained the same.
In conclusion, Wallop said seabass can eat the fish fry, but not the small fry because they are carried in the mouth of the male fish.
There is also a great deal of vegetation in natural watercourses, where the fry and small fish can hide.
He also noted that, if too many seabass are released into watercourses, people switch to catching the seabass instead of Blackchin tilapia.
He suggested that the plan by state agencies to buy Blackchin tilapia, for turning into animal feed, must be long term and without restrictions, otherwise there will be no incentive for people to catch them and they will proliferate again, if not completely eradicated.
Another shrimp farmer in Amphawa district, Natthaphon Khemkamnerd, said he raised shrimp on his farm of over 80 hectares about a decade ago and he managed to harvest not only shrimp, but other fish as well.
In 2011, when Blackchin tilapia started to spread on his farm, he said all his shrimp were wiped out. He tried to raise shrimp again, but they were all eaten by the alien fish species.
Natthaphon said that he discovered that Blackchin tilapia eggs are very resilient, even though he let his ponds dry out for about two months.
When the rains came, however, he found the pond was soon full of Blackchin tilapia fry.
He a finally gave up shrimp farming and turned to raising seabass instead, which didn’t work either because the fish did not fetch a good price.
He said his farm is less than 500 metres from an experimental fish farm, operated by a private company believed to be Charoen Pokphand Foods (CPF).
CPF imported 2,000 Blackchin tilapia from Ghana in 2010 for research and species improvement, but most of them died before arrival in the country.
The rest later died, prompting the company to cancel the project. It claimed, however, that it had properly disposed of the dead fish.
Natthaphon questions whether the company did properly disposed of the dead fish, claiming that he was one of only two people in Samut Sakhon who owned and rented out backhoes.
He believes that, although the dead fish were buried, their eggs might have survived and developed into fry when the rain came, which could be how the fish started to spread in the province.
