Exotic Aquatic Organisms - International Development Research ...

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long time ago as shown by the fact that three genera and all of the species of cyprinids living
there are endemic to the Lake.
Introduction of exotic species into the different islands from other islands of the country or
from other countries, requires serious study and careful consideration, particulary on adverse
effects such introductions may produce on endemic and indigenous species. Government should
adopt strict policies and guidelines to regulate introduction of exotic species. Almost all aquatic
introductions into the country were meant to benefit the country, through aquaculture, capture
fisheries, or for biological control purposes. However, the benefits that were derived did not
really outweigh the adverse effects that came about as a result of some of the introductions.
There were introductions of exotic aquatic species that were done by individua:ls without the
knowledge of the Government. Even in pet shops in Manila, exotic species of fishes can be
found which were brought into the country without government clearence. Certain species that
are or were available for purchase from pet shops or dubious sources are species of Serrasalmus
(pirranha), Pangasius and other catfishes. Such exotic species fortunately are not yet found in the
wild and are evidently confined as pets for the time being. No action on the part of the
Government has been observed to regulate such introduction.
Recorded Exotic Fish Species in the Philippines
The first recorded introduction of an exotic fish species to the Philippines was in 1907 when
Mr. Alvin Seale was authorized by the Philippine Insular Government to import from California,
fingerlings of largemouth bass, Micropterus salmoides. Introductions as a food fish and for sport,
were made in ponds and lakes specially in higher altitudes in the Mountain Province (Baguio
City) and Caliraya Lake in Laguna Province. This species does very well in higher altitudes
where temperatures are the same as subtropical zones. Luckily, this fish did not thrive in
lowlands where many lakes abound. It is only in Lake Caliraya that M. salmoides is known to be
doing well, at 700 meters above sea level, and in 1985 another related species, Micropterus
salmoides floridanus was received as a gift from California and stocked in Caliraya Lake (a
reservoir). Bass fishing tournaments are held in this reservoir regularly.
Subsequently, other introductions of aquatic species, mostly fish, were made with reasons
that varied from providing more food fish for the country in lakes and rivers, for aquaculture
purposes, for biological control of undesirable species such as mosquitoes and weeds, for sport
fishing and others. Some of the introductions became nightmares for aquatic-based industries
like the brackishwater farming industry; for e.g., introduction of Mollienesia latipinna (molly)
for the purpose of controlling malarial mosquitoes. The mosquito fish, however, became a pest
in brackishwater ponds. Other fish species introduced for control of mosquitoes were Gambusia
affinis, Poecilia reticulata and Fundulus heteroclitus. The introduction of Tilapia mossambica
(Mossambique tilapia) was a real nightmare for brackishwater farming, competing for food in
the farm with Chanos chanos (milkfish). The Mossambique tilapia is now an established species
in brackishwater farms in the entire country.
The Philippine freshwater catfish, Clarias macrocep ha/us, became completely dominated by
an exotic species, C/arias batrachus, imported from Thailand during the craze for catfish
farming patterned after the success in Thailand. Clarias batrachus now dominates natural
populations in lakes and rivers and the indigenous C. macrocephalus can hardly be found in the
markets nowadays. C. macrocephius has better qualities as a food fish compared to C. batrachus.