A brief review is given of those physical features of San Miguel Bay, Philippines, which have an impact on the Bay's fisheries. These features are: the climate conditions, notably the strong winds during the northeast monsoon; the oceanographic conditions, notably the estuarine habitats created within the Bay by the freshwater inflow from the Bicol River and by the heavy rainfall; and the siltation of the Bay by upland erosion which is gradually making the Bay shallower, thus reducing those areas legally and physically accessible to commercial-sized vessels.