Typical – and alarming – example is the fish population in Lake Lanao in Lanao del Sur.
At the early part of the 20th century, the vast lake nurtured 17 species of cyprinids (carp family).
However, a survey done by Prof. Pedro Escudero of the Mindanao State University (MSU) in Marawi City in 1990-91 showed that only two species of the important fish species were found.
Efforts are now being exerted to ensure the survival of the remaining species.
The loss was attributed to heavy predation of the cyprinids by the white goby and the eleotrid that were inadvertently stocked in the lake with Nile tilapia fingerlings coming from a government hatchery in Surigaio del Norte, noted Executive Director Rafael D. Guerrero III of the Los Baños-based Philippine Council for Aquatic and Marine Research and Development (PCAMRD).
In the 1970s, too, the massive dispersal of the Thai catfish in Luzon led to the displacement of the native catfish (hito) in irrigation systems, lakes, and rivers.
"The introduced fish was not acceptable to local consumers because of its tough flesh," averred Dr. Guerrero in a report. However, it successfully established itself in freshwater bodies not only in Luzon but also in Negros, Panay, and some parts of Mindanao.
Another "alien invasive species" (AIS) now wreaking havoc on the country’s ecosystem is the golden apple snail (GAS), which was introduced as and aquarium novelty in the Philippines in the early 1980s by a local pet shop firm with no government permit.
Because of its superior growth and breeding qualities compared to the native "kuhol," the GAS was promoted by the private sector with government support as a source of animal protein for humans and livelihood provider.
"Its acceptability to consumers, however, was not as expected," Dr. Guerrero said. "The much ballyhooed livelihood projects for it nationwide were dropped and the unwanted species was dumped into canals, rivers, and lakes. The alien snail also displaced the native kuhol."
The PCAMRD official cited the three cases to underscore the importance of implementing comprehensive protection and management program to ensure the conservation of the country’s freshwater endemic fishes and save them from the onslaught of introduced alien invasive species.
Dr. Guerrero was among the resource speakers at a seminar-workshop on AIS held not long ago in Quezon City.
The national scientific forum was organized by the Los Baños-based ASEAN Regional Center for Biodiversity Conservation (ARCBC) with the cooperation of the Department of Environment and Natural Resources-Protected Areas and Wildlife Bureau (DENR-PAWB).
Alien invasive species have been described as plants, animals, and microbes not native to a region which, when introduced accidentally or intentionally, out-compete native species for available resources, reproduce prolifically, and dominate regions and ecosystems.
Typical examples of destructive AIS are the Thai catfish and golden kuhol, which has become a serious pest throughout the country, attacking rice, corn, ornamental and other plants.
Dr. Guerrero also reported that two alien fish species not yet considered invasive but on the "watch list" are the African catfish and the South American catfish.
The African catfish was introduced in 1985 by the private sector from Taiwan. It is now contributing to food supply in the Ilocos Region, Central Luzon, Southern Luzon, Western Visayas, and some parts of Mindanao.
However, African hito is predatory in the wild and carnivorous in captivity, preying on small "ayungin," carp, and tilapia.
The South American catfish was introduced in the country in the 1990s by the aquarium trade industry as a "janitor fish". Escapees of the fish in flood-prone areas have "invaded" Laguna de Bay.
"No adverse reports on the impact of the catfishes have yet been documented," Dr. Guerrero added.
Summing up, he stressed that, based on the country’s experiences with AIS, "not all that are good for other countries is good for us. In fact, it can be a big problem."
The PCAMRD official thus advocated that existing quarantine regulations be strictly enforced. He also recommended that introduced species should be properly evaluated before these are released into the environment.