Chemical and Microbial Analyses of Organic Milkfish Farm in Negros Occidental, Philippines

This study was undertaken to provide baseline information on the chemical and microbial profiles of a milkfish farm that practices organic aquaculture in a brackish water system. A one-hectare pond from the total of 13-ha. farm was subjected to chemical and microbial analyses for two production cycles from August 2015 to May 2016. The owner followed the organic milkfish farming protocol practiced since 2009. The pond was fertilized with vermicast and stocked with wild-caught milkfish fingerlings of 2- 3 inches body length. Soil and fertilizer profiles, water quality, heavy metal, and antibiotic residues were analyzed. Production data were taken to compare survival between dry and wet seasons. Soil and fertilizer analyses showed high levels of magnesium, iron, manganese, copper, and nickel, but nil for cadmium. Water analyses showed positive for Escherichia coli, with the highest level of 220 MPN/100 ml from the water source during the wet season. Harvested milkfish were found negative to the antibiotic’s chloramphenicol and nitrofuran; but positive to cadmium at 0.24 mg/kg. Milkfish production was higher during the wet season, with 86% survival, compared to the dry season with 70%. All the parameters analyzed were within limits, except for cadmium, and bacterial contaminations observed higher in the water source during the wet season. Results suggest the potential of organic aquaculture in brackish water systems. However, a scheme to decrease microbial and chemical contaminations, such as a bio-filtration system is recommended, especially for farms that have open water sources like brackish water fishponds.

Keywords: organic aquaculture, brackish water aquaculture systems, heavy metals, antibiotic residue, microbial load