Imported ‘invasive’ species threaten Philippine fishery industry

LOS BAÑOS, Philippines  – Invasive fish species were among 60 species introduced in local inland bodies of fresh water over the past century, a study said.

The exotic fishes from other countries have been in the Philippines since 1905.

However, some were introduced for food production, recreational fishing and ornamental purposes without authorization from the Bureau of Fisheries and Aquatic Resources (BFAR) of the Department of Agriculture.

“Many introduced fishes have become invasive, causing ecological damage, economic loss, and even human injury.” Six fish species became invasive upon escaping “accidentally or intentionally” into open waters from commercial and private keepers, according to aquaculture scientist Rafael Guerrero III of the National Academy of Science and Technology (NAST).

In the report titled “Introduced Freshwater Fishes in the Philippines: An Assessment and Recommendations” published by NAST, Guerrero identified some of the invasive fish species and these are the following:

Janitor fish – This fish, particularly the Pterygoplicthus disjunctivus species, has reduced the fish catch of fisherfolk using fish corrals and gill nets in Laguna de Bay and Agusan Marsh in Mindanao, resulting in huge economic losses. The burrowing habit of the other janitor fish, P. pardalis, has also eroded the banks of Marikina River, a tributary of Laguna de Bay.

Clown knife fish – Believed to have escaped into Laguna de Bay after a flooding caused by Typhoon Ondoy in 2009, this fish is now wreaking havoc on the milkfish and tilapia industries of the lake.

Giant snakehead – This fish is present in the Pantabangan reservoir in Nueva Ecija although its invasiveness is not yet very serious, according to Guerrero.

Black-chin tilapia – This was first observed in Laguna de Bay but it eventually spread to the brackish waters (mixed fresh and salt waters) of Bulacan. Its presence is not yet much of a concern.

Jaguar guapote – This has been preying on and competing with native fishes in Taal Lake in Batangas.

Meanwhile, the red-bellied piranha (Pygocentrus nattereri), peacock bass (Cichia occularis) and araipama (Araipama gigas), which were introduced for ornamental purposes, have been deemed to be potentially invasive and need close watching because of their predatory habits, capability of spawning in tropical waters, and bio-invasive records in other countries, according to Guerrero.

The BFAR did not approve the introduction of piranha and bass, so these species should be on the watch list.

The mudfish (Channa striata), Thai catfish (Clarias batrachus) and rice paddy eel (Monopterus albus) which were introduced for aquaculture have also become invasive.

The mudfish is a pest in freshwater ponds since it preys on cultured species like tilapia.

The Thai catfish ecologically displaced the indigenous catfish (Clarias macrocephalus) in Laguna de Bay and other water bodies where it was introduced.

The rice paddy eel is reportedly infesting rice paddies in the Cagayan Valley by burrowing into dikes and causing water losses.

Guerrero underscored the need to strengthen the monitoring, surveillance, and control measures to prevent the spread of invasive ornamental fishes established in some of the country’s inland waters and to forestall the escape of the potentially invasive species into open waters.

“The regular inspection and possible registration of aquarium pet shops and a massive information, education, and communication campaign to stir up public awareness for responsible aquarium pet care and environmental protection are recommended,” he said.