Pollution-Induced Fish Kills in Bolinao: Effects of Excessive Aquaculture Structures and Overstocking

In the Philippines, Lingayen Gulf is one of the main producers of aquaculture. In 1992, the Lingayen Gulf Coastal Area Management Plan (LGCAMP) was formulated to regulate aquaculture industry. Bolinao was one of the municipalities surrounding the Gulf identified to be suited for coastal or marine aquaculture production. Since 1995, the number of aquaculture structures in Caquiputan Channel, Bolinao continued to increase to the point that it exceeded the carrying capacity of the Channel. Despite the ordinances, aquaculture operation was not regulated. Overstocking and excessive feeding practices have been reportedly done in the area. These practices, together with excessive number of structures, were claimed to have caused deterioration in water quality that, in turn, have caused fish kills in the area. This study was conducted to assess the effects of excessive aquaculture structures and overstocking on water quality and aquaculture production in the area. Water quality analysis done in the sample fishpens revealed that on the average, the DO levels in areas with aquaculture structures were below the critical value of 5 mg/L for fish growth. TSS values were also reasonably high in aquaculture sites compared to the non-aquaculture areas. Stocking density was found to be negatively correlated with DO values. Cost and return analysis revealed that aquaculture operation is a lucrative business but the at the same time, the management practices have negative effects on the industry itself. Aquaculture production analysis showed that stocking density tends to have negative effects on production if stocking density exceeded 1,693 frys/100 m2 fish pen area. Water quality dummy also indicate that the poorer the water quality in terms of DO value, the more likely that production will decrease. Among the policy implications forwarded from the results of the study include: strict enforcement of the ordinances, provision of resources for activities toward sustainable aquaculture, and enactment of legislation.