During the 40 years of work on coastal and marine areas, we have identified several useful indicators of highly productive marine ecosystems. It may be good to enumerate these indicators for the guidance of environmental organizations, local government units, and national agencies especially the Department of Environment and Natural Resources and the Bureau of Fisheries and Aquatic Resources that are concerned with the productivity and integrity of coastal ecosystems.
For coral reefs in general, the occurrence of moderate to strong ocean currents and the clarity of seawater would appear to highly influence the recovery of corals that are damaged by typhoons. We have observed rapid recovery of a coral reef in Tañon Strait in the 1980s.
This contrasts with the very slow growth of both massive and branching coral species in highly turbid waters off Sultan Kudarat and Maguindanao provinces in western Mindanao. Coral growth was practically zero during the three years of study from 2002 to 2005. During this period of time, fish biomass grew slowly–less than 10% per year from an initial very low biomass of about 2-4 tons per square kilometer, despite protection from fishing of the no-take reserves. The sediments entered the marine environment through two large rivers in the area and were carried seaward for some 22 kilometers. In these two examples, there could have been other human-caused conditions that further exacerbated the situation.
A similar finding was made in southwestern Negros, where a river deposited loads of sediment on a small barrier reef at Caliling in the town of Cauayan. This reef had excellent coral species composition and a high diversity of fish species and other marine species prior to the massive destruction of the tropical rain forest drained by the Caliling River in the decades of the 1950s, 1960s, and the 1970s. I estimate the fish biomass on this reef at not less than 100 tons per square kilometer in the decades of the 1930s and 1940s. Now, both coral diversity and fish diversity is very low. Coral reef fish yields are very insignificant at this time and are not worth writing about.
All over the Visayas, the majority of unprotected reefs, seagrass, and soft-bottom areas along the coast have generally no more than 5-10 tons of fish biomass per square kilometer of marine space. Many reefs are silted. Most coral species belong to the resistant species like massive corals and practically none of the branching species and other coral lifeforms that provide a variety of microhabitats for various species of fish. Under these conditions, one cannot expect fishers to have substantial fish catches. In fact, our records of fish catch of fishers using the hook and line fishing gear indicated that their catch is hardly half a kilogram per hour of fishing per person. This is obviously too low to support the fish food needs of a family.
To sum up, the indicators of a good and productive coastal environment include a good live coral cover (50% and higher) consisting of a variety of species, a clean sediment-free water, a good water circulation, a high species diversity of fish and other reef species like clams and sea cucumbers, a variety of marine microhabitats (coral reef, mangrove, seagrass), proximity to a deeper body of marine water with an upwelling that keeps the shallow waters cool at all times, and proximity within tens of kilometers to other similar areas. One way to improve the productivity of our coastal waters is to identify and protect such areas all over the country.