49 Philippine Journal of Science 143 (1): 49-59, June 2014 ISSN 0031 - 7683 Date Received: 06 January 2014 Key Words: Alien species, Aquaculture, Exotic species, Fisheries, Introductions, Invasive species *Corresponding author: aquabios@yahoo.com Rafael D. Guerrero III National Academy of Science and Technology, Philippines Philippine Heritage Center, DOST Compound, Metro Manila, Philippines Impacts of Introduced Freshwater Fishes in the Philippines (1905-2013): A Review and Recommendations Based on existing records and observations, 62 freshwater fishes were introduced from 1905 to 2013 in the Philippines for aquaculture (45%), ornamental purpose (42%), recreational fishing (6%), and mosquito control (6%). An evaluation showed that 48 (77%) of the fishes are beneficial, 10 (16%) are invasive, and 4 (6%) are potentially invasive. In terms of of economic benefits, the gains derived from the introduction of beneficial fishes, particularly for culture and fisheries enhancement, are much more compared to the economic losses due to the negative impacts of invasive fishes. A review of the national policies and regulations on the introduction of imported live fishes showed that the required processes are adequate and in place. However, there are gaps that need to be urgently addressed to strengthen monitoring, surveillance and control to prevent the spread of the six invasive ornamental fishes now established in inland waters and to forestall the escapes of the potentially invasive fishes. INTRODUCTION With globalization, the transport of plants and animals from one country to another through human intervention has been facilitated. The intentional or unintentional introduction of living organisms for economic and other reasons can have beneficial or adverse impacts (Bruton & Merron 1985; De Silva 1989). Next to habitat destruction, the introduction of “invasive species” is the second major cause of loss of biodiversity (IUCN 1999). Introduced aquatic animals such as fishes are defined as those that have been transported into aquatic habitats outside their native range for the species (ICES 2003). Exotic or alien species are those that have been transferred from one country to another or from one body of water to another where they are non-native. Invasive alien species is defined by the Convention on Biological Diversity (2014) as “species whose introduction and/or spread outside their natural past or present distribution threaten biological diversity.” Introduced aquatic species may have environmental, social and economic impacts. Species introductions can improve production and economic benefits from fisheries and aquaculture. It has been estimated that 17% of the world’s finfish production is attributed to alien species. Such species have “more positive socioeconomic benefits reported than negative ecological impacts” (FAO 2014). Exotic fishes capable of breeding naturally in areas where they are introduced can become established with “open or occupied niches” and replace local species due to their “numerical and/or fitness advantage” (Stachowicz & Tilman 2005). Invasive fishes can also cause genetic pollution with “uncontrolled hybridization, introgression and genetic swamping” (Mooney & Cleland 2001). According to the Global Invasive Species Programme (1999), “invasive alien species are a global threat whose impacts cost at least US$ 1.4 trillion annually and will have to be managed in perpetuity.”