The study was conducted to assess the species composition, abundance and diversity of fish including physico-chemical characteristics of the Minalin Channel-Pampanga River Basin during dry season (February - April 2018) and wet season (July - September 2018). Findings showed that 24 fish species (16 fresh water and 8 marine) where identified representing 16 families (9 fresh water and 7 marine). The most abundant species recorded are E. hawaiiensis and S. melanotheron during dry season. Likewise, over-all catch of species is more abundant in the dry season. This shows that dry season has higher diversity index compared to wet season. This result could be linked to the seasonality of some species in the fishing area. The seasonality is related to the biology requirements of fishes and external factors that influence these requirements. As to the physicochemical characteristics of the river, the result of the study showed an abrupt change of salinity from 11.57 ppt in the dry season to 0 ppt in the wet season. This variation could be linked to the drop of temperature and increase of water inputs during wet season. The decrease in temperature observed during wet season could be directly linked to minimal sunlight that reaches the surface and subsurface layer of the river caused by huge amount of precipitation. This seasonal variation in catch composition and abundance could be a function of seasonal change in habitat condition which affects diversity indices.
