The Philippines Pampanga River Scores well in IBI ecological test

Rivers have been important sources of drinking water, food, and livelihood since the beginning of human civilizations and until now, communities depend on the sustenance rivers provide.

However, they have been utilized for so long that nature has shown signs of ecological imbalance due to widespread pollution, continuous human activities, and natural phenomena. One such resource is the Pampanga River, the fourth largest basin in the Philippines, coursing Central Luzon from Pantabangan Dam in the northeast to Manila Bay in the southwest.

Many methods have been developed in order to study and monitor river conditions. Conventional tools currently used in the Philippines, however, like physico-chemical monitoring which only analyzes elements such as temperature and level of nutrients in the water, have been proven by previous studies to be insufficient in detecting pollutions in the aquatic environment. Thus, additional methods have been developed which include the Index of Biotic Integrity (IBI).

The study Assessment of the Fish Population in Pampanga River, Central Luzon, Philippines Using the Index of Biotic Integrity (2005) by Sheryll P. Angeles of the University of the Philippines’ Institute of Environmental Science and Meteorology evaluates the effectiveness of the IBI through its assessment of the condition of the Pampanga River. Based on the study, biotic integrity is “the ability of an ecosystem to support and maintain a balanced, integrated, adaptive biological system having the full range of elements and processes in the natural habitat of a region.” The IBI measures the quality of water through metrics that reflect fish species richness and composition, fish abundance, and condition of individual fish. High IBI scores indicate relatively high number of total species present, high overall fish abundance, and low number of hybrids and fish with disease or deformities. High IBI scores therefore imply good quality of water and habitat.

The combination of the IBI and the physico-chemical analysis is used to analyze the fish population. The IBI metrics are modified to match the fish assemblage of the Pampanga River. Fish sampling was done quarterly from four sampling sites from January to November 2004. Site A is located at Val de Fuente, Cabanatuan, Nueva Ecija; site B at Cabio, Nueva Ecija; site C at San Luis, Pampanga; and site D at Apalit Pampanga. A total of 2,657 fishes were caught and were found to belong to 25 species and 14 families.

Using the IBI, three major metrics were measured to assess the aquatic environment of the Pamapanga River: species richness and composition (total number of species, native and intolerant), trophic composition (omnivorous, invertivorous[1], carnivorous), and individual abundance and condition (total number of native fish individuals and percent of fish with anomalies).

Results show that fishes that can endure extreme changes in the water condition or tolerant fishes such as the Leiopotherapon plumbeus (Ayungin) and the Oreochromis niloticus (Nile Tilapia) dominate the river. Several other exotic and tolerant species exist in all sampling sites, which, according to Angeles, is an alarming situation that should not be taken lightly because of their possible contribution to further destabilize the riverbank structure.

These kinds of species include the Pterygoplicthys pardalis (Sailfin Catfish) which is very tolerant and proliferates very fast and the Hypostomus plecostomus (Suckermouth Catfish/Janitor Fish) which has already caused bank erosion in the Marikina River. Native and intolerant fishes also breed in sites that may be considered with fair to excellent environmental conditions. Intolerant species found in the Pampanga River were Butis butis (Duckbill Sleeper), Butis gymnopomus[2], Glossogobius cellebius (Biyang bato/Ipon), Valamugil engeli (Talilong), and Scatophagus argus (Kikiro/Kitang).

Variations in the condition of the sampling sites are found to affect significantly the IBI scores collected in the Pampanga River. In site A, shallow depth and low water volume due to the presence of dams were said to have possibly caused the drop in fish abundance and diversity. In October 2004, IBI scores rose because of heavy rains that washed the upstream fish population downstream, thus, increasing fish abundance and diversity. In November, IBI scores dropped once again because of continuous rains which washed the fishes further downstream resulting in a decline in fish population. Low IBI scores were recorded in site D, which, based on the study, were possibly due to “high levels of phosphates, total dissolved solids, nitrate-nitrogen, and fecal coliform.” Therefore, the number of native intolerant species decreases while the number of tolerant species increases. Based on these results, the status of the Pampanga River is found to range from fair to excellent due to the evidence of native and intolerant species even if tolerant species dominate the river.

The Index of Biotic Integrity has performed well in determining the environmental condition of the Pampanga River through the assessment of the fish population. Its application can be adjusted to the water conditions of tropical regions so it is an effective method of analyzing the Philippine aquatic systems. However, the author still recommends a thorough study of this method for a more reliable evaluation and monitoring of water conditions.

References:
1. “An Introduction to the Index of Biotic Integrity.” Biological Indicators of Watershed Health. U.S. Environmental Protection Agency. August 2007.
2. Froese, R. and D. Pauly. Editors. 2007. FishBase. World Wide Web electronic publication. www.fishbase.org, version (07/2007).

[1] Invertivorous species or invertivores are fishes that feed on invertebrates.
[2] No common name given or available.