Fish Ark Philippines: direction for the conservation of native and endemic Philippine Freshwater Fishes Project 1: Survey of diminutive freshwater fishes indigenous to isolated crater lakes, mountain crater lakes, mountain streams and cataracts in Southern Luzon, Philippines

Ichthyofaunal surveys were conducted from Aug 2008 to July 2011 to evaluate the conservation status of freshwater fish communities and record the environmental conditions of 27 aquatic sites representing seven study areas with isolated crater lake, mountain streams, and waterfalls within Southern Luzon, Philippines. The survey inventoried at least 72 different fish species belonging to 58 genera and 27 Families. Native species comprised approximately 75% (54 out of 72) of the total fish identified. Family gobiidae largely dominated the native species at about 30% (16 out of 54). However, a large percentage of the fish community was introduced such as cichlids, cyprinids, and poeciliids, suggesting established feral populations of exotic species in natural aquatic habitats of the Region. Further, Oreochromis niloticus was one of the most frequently captured and the most widely distributed among the introduced ichthyospecies, or if not, among all the fishes surveyed. Ichthyofaunal compositions for each site was assessed by calculating the various biotic indices such as Shannon diversity index (H'), Pilou's Evenness Index (e), Simpson's species dominance index (c), and fish density (d). Biotic indices showed highly diverse conditions (H' greater or equal to 1.5) among species in some less disturbed areas and during the wet season. Likewise, species richness and total abundance in the sites were both found to increase during the wet season of the year. Geological and hydrological features of the aquatic ecosystems, presence of diversified micro-habitats, seasonal changes, dense vegetation, and connection to adjacent seas are the main contributory factors structuring the fish assemblages and the equitable distribution (greater or equal to 0.6) of dominant and non-dominant fish species. In contrast, anthropogenic-induced modification in habitats, occurrence of invasive alien species, pollution, and climate change may negatively altered the function and structure of aquatic biota. Significant spatial and temporal differences (p0.05) on physico-chemical parameters were recorded. Freshwater fishes accounts recorded from the survey and proposed IUCN status of freshwater fish natives were also provided. The survey also updated the list of freshwater fish fauna of Southern Luzon.