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Abstract. The topic on freshwater resources on the rivers and lakes in the Philippines is strangely under researched despite its economic and ecological importance. There is very little research on freshwater fish biota in the numerous islands of the archipelago that this paper will remedy this omission. Field works were done from October 2017 to February 2018 to determine the freshwater fish resources found in Pajo-StoDomingo (PSD) river system in Virac, Catanduanes Island, Luzon. A total of 12 families (Ambassidae, Anguillidae, Atherinidae, Cichlidae, Cyprinidae, Eleotridae, Gobiidae, Mugilidae, Channidae, Osphronemidae, Sparidae, Terapontidae); 18 genera and 20 species of fish fauna were identified in the study areas, higher than the previous studies. The most speciose families are Cyprinidae, Gobiidae and Mugilidae, with three species each, followed by Ambassidae and Eleotridae with two species each, and then the rest of the families with one species each.
Key Words: Catanduanes, diversity, fish abundance, fish fauna, freshwater systems, streams.
Introduction. The review of Magbanua et al (2017) provided indications that further research is needed in freshwater systems wherein organisms thriving in rivers and streams have been neglected in the Philippines. From a total of 281 papers reviewed, only 78 papers were on freshwater fish and the rest were on zooplankton (Aquino et al 2008), and algal bloom occurrence in Laguna de Bay lake (Baldia et al 2003). It was Papa & Mamaril (2011) who traced the history of biodiversity and limno-ecological studies on Lake Taal and have recommended the need for more in depth researches about this inland body of water in the Philippines.
Despite the importance of biodiversity in rivers in tropical Asia, this has been neglected compared to its temperate counterpart (Dudgeon 2000a; Dudgeon et al 2006). Recent situations indicate that these aquatic ecosystems have suffered from intense human intervention resulting in habitat loss and degradation and as a consequence many fresh water and estuarine fish species have become heavily endangered (Dudgeon 2000b; Strayer & Dudgeon 2010; Magbanua et al 2017).
In many southeast and east Asian countries like the Philippines and India, river basins receive heavy demand for the economic and industrial uses of fresh water. This is coupled with irreversible changes in natural population by introduction of exotic species and diseases (Pusey et al 2004;...