MICROBIOLOGICAL QUALITY OF OYSTERS (Crassostrea iredalei) PRODUCED IN THE COASTAL AREAS OF PANAY ISLAND, WESTERN VISAYAS, PHILIPPINES

Rolando Pakingking Jr.¹, Lilibeth Hualde¹, Ernestina Peralta² 

¹Aquaculture Department, Southeast Asian Fisheries Development Center

(SEAFDEC AQD), Tigbauan 5021, Iloilo, Philippines

²Institute of Fish Processing Technology, University of the Philippines Visayas,

Miag-ao 5023, Iloilo, Philippines

e-mail: rpakingking@seafdec.org.ph 

The increasing demand for slipper-shaped oysters (Crassostrea iredalei) has propelled farmers to expand oyster culture areas in the Philippines. Stake method has by far been predominantly practiced. Because oysters are filter feeders capable of ingesting particles in suspension containing pathogenic microorganisms that can cause human foodborne diseases, continual monitoring of oyster production areas for microbiological quality is indispensable. In this respect, the major oyster producing sites located along the coastal villages of Roxas City (Culajao [n=3 sampling stations] & Cagay River [n=5]) and municipalities of Ivisan (Cabugao Bay [n=7]) and Panay (Culajao River [n=5]), Capiz province, Panay, Western Visayas, Philippines, were examined monthly for their microbiological quality, i.e. quantity of Escherichia coli, Vibrio cholerae, V. parahaemolyticus, and Salmonella in oysters’ meat and intervalvular fluid and fecal coliforms of the rearing water, over a period of 2 years.

The monthly coliform count in the water samples collected from all sampling stations were generally high (≤ 540 MPN/100 ml) regardless of the sampling period (wet or dry season).  Similarly, the monthly E. coli count in oysters’ meat and intervalvular fluid were typically high (330~24,000 MPN/100 g) particularly during the warm dry months of the year, i.e. April to June. V. cholerae was not detected in any of the oyster samples examined while V. parahaemolyticus count was within acceptable range. Salmonella was erratically detected in oysters collected from all sampling stations examined. Relaying oysters in an approved area in Cabugao Bay was likewise attempted. As a result, E. coli countin contaminated oysters significantly dropped from 24,000 MPN/ 100g to ≤ 20 MPN/ 100g after 2 weeks of relaying, suggesting the practicality of this technique in rendering raw oysters safe for human consumption.

Taken together, current data indicate the urgent need to improve the quality of raw oysters cultured in these sites through the adoption of environment friendly culture methods such as raft or long line together with the establishment of a National Shellfish Sanitation Program whose primary task shall include continual monitoring of the microbiological quality of oysters and their culture environments.