A neglected ecosystem in the Philippines is the estuary, defined as “a semi-enclosed coastal body of water with free connection with the open sea, and within which sea water is usually diluted with freshwater derived from land drainings.”
Authorities recognize four types of estuaries from the geomorphological standpoint but one additional type called “river delta estuary” found at the mouths of large river systems is common throughout the country.
Large estuaries are found in the tropics, and play important roles in fishery as nursery grounds for certain fishes and crustaceans.
The larvae and juveniles live in the safety of estuaries until they reach a certain developmental stages when they are able to colonize far-flung and larger ecosystems in which to spend the rest of their lives.
Other economic benefits from estuaries include fishery yields and ecological tourism.
Furthermore, estuaries are thought of as multiuse systems for humans; they are used as fishery grounds, as transport areas for human commerce and trades, as receptacle for wastes, as sites for human habitations, etc.
It is precisely these uses, which are often competing, that lead to the environmental degradation of estuarine ecosystems. Once this happens, estuaries become useless for any gainful and sustainable human activity.
Estuaries are prone to perturbations resulting from both human and natural activities such as sedimentation and eutrophication (excessive nutrient pollution).
In addition, these stressors may be exacerbated further by the effects of climate change such as increased flooding and extreme drought resulting to alteration in species composition.
There must, therefore, be a careful balancing in the human use of estuaries to keep their integrity, and this requires research and firm action by political authorities.
It is common knowledge that Philippine estuaries abound in aquatic species, many of which are used as food by people living in the vicinity of these ecosystems.
The fact that estuaries serve as source of food is one of the major reasons why people live near or in estuaries.
But the quantity of food derived from estuaries is generally not known, and this requires research.
What is known through the published records made by fishery scientists beginning in the early decades of the 20th century are the various species of fish found in river systems of the Philippines.
A number of Filipino scientists in the 1920s through the 1950s have published in the Philippine Journal of Science accounts of marine fishes occurring in rivers.
A.W.C.T. Herre, an American scientist and friend of the Philippines, in 1953 and 1958, summarized the findings of these papers, and reported a total of 268 species of marine fish in rivers and lakes in his Lists A and B.
All of these fishes, of course, entered rivers through the estuaries, and a number of them inhabit the freshwater portions of these rivers for most of their lives.
Many of these species such as the gobies, Eleotrids, and eels live in freshwaters but spawn in the sea.
Some of them, such as the mangrove jack, are nursed in the estuaries before they colonize marine habitats. Still others are typically estuarine species throughout their life history, such as groupers and mullets.
It would be of interest in terms of ecological knowledge and conservation to know to what extent the earlier findings in the early and middle decades in the 1900s are still true today, that is, how many of the 268 species listed by Herre (1858) are still using the estuaries as their habitats.
To answer this question, the SU-Angelo King Center for Research & Environmental Management (SUAKCREM) is conducting research studies on estuaries beginning with those on Negros Island.
