BFAR told mosquito fish is ‘invasive alien species’

DAGUPAN CITY—An environment official on Friday sounded the alarm over the release of thousands of mosquito-eating fish in canals and waterways in Pangasinan, saying it is “a highly invasive alien species.”

Theresa Mundita Lim, director of the Department of Environment and Natural Resources’ Protected Areas and Wildlife Bureau (PAWB), said “further and intentional release of the mosquito fish into the waterways may bring more serious implications and irreversible damage to our already fragile biodiversity.”

“May we then request that the BFAR (Bureau of Fisheries and Aquatic Resources) exercise caution in the release of these fish species. Any release should be administered in a controlled condition and covered by environmental safeguards,” said Lim in her letter to BFAR Director Asis Perez. A copy of Lim’s letter was posted on her Facebook account.

Lim wrote Perez after the National Integrated Fisheries Technology Development Center (NIFTDC), a research arm of BFAR here, started stocking canals and waterways in different villages in Dagupan with thousands of mosquito fish (Gambusia affinis) to help check the spread of dengue fever cases in this city. Dengue is a mosquito-borne disease.

But Westly Rosario, NIFTDC chief, said the mosquito fish has been in the country for decades and has no negative effects on the environment and with other species.

“Whether we like it or not, that fish is already here. There were a lot of species introduced in the country in the past that were not properly monitored,” Rosario said by telephone.

“Among those species, the mosquito fish is one of those that had good use. If this created a problem, we should have felt it in the past,” he said.

Rosario said BFAR practices “responsible stocking.”

“You do not put these in running rivers. Besides, these die when a river has a lot of water lilies. And when the water gets shallow, these fish are eaten by birds and other fish, such as the mud fish,” he said.

Lim said that as a highly invasive species, the mosquito fish has the ability to establish their population outside their natural habitat then “invade, out-compete natives and take over the new environments.”

She said experts have identified the mosquito fish as one of the world’s worst invaders.

She said the Global Invasive Species Database (GISD) had tagged the mosquito fish as a pest in many waterways around the world after initial introductions as a biological control agent for mosquitoes.

In its website, the GISD said the highly predatory mosquito fish eats the eggs of “economically desirable fish” and preys on and endangers rare indigenous fish and invertebrate species.

“Mosquito fish are difficult to eliminate once established, so the best way to reduce their effects is to control their further spread,” the GISD website said.

Rosario said his agency, last year, released some 200,000 mosquito fish in waterways in western Pangasinan towns to complement the effort to stop the breeding of dengue-carrying mosquitoes (Aedes aegypti). “In fact, they are asking for some more,” Rosario said.

He said the mosquito fish are stocked only in confined places, such as canals and sewers, and not in flowing bodies of water, like rivers.

“This is for the biological control of mosquitoes and you stock them in the mosquitoes’ breeding ground,” Rosario said.

He said mosquito fish that found their way into the rivers are caught, along with other small fish, for consumption.

“These can also be food for sea bass and other carnivorous fish species,” Rosario said.

Lim said people should realize that native species have been placed in the country’s natural ecosystems to address mosquito and pests problems.

“But we have not protected them and are even [exterminating] them, such as our tuko (gecko) and native gobies,” Lim said.

“The BFAR should start focusing on propagating our local species. Haven’t we learned our lesson from the knife fish and the janitor fish in the country?” she said. Gabriel Cardinoza, Inquirer Northern Luzon