Biofouling and its Possible Modes of Control at Fish Farms in Penang, Malaysia

Abstract

Biofouling by 13 selected organisms was monitored with regard to their settle• ment patterns and their suppression by three types of chemicals. Their settlement patterns over a period of 180 days within a depth range of 1.5 m can generally be divided into three types. The early settlers colonizedthe substrata within the first two months of submergence and disappeared towards the end of the experiment. The second type also reached a peak density sometime during the first or second month, but declined slightly at the end. The late settlers started to appear only on the second or third month and their numbers were mostly sustained till the end. However, the distribution of all the organisms except barnacles and tunicatea was random within the depth range studied. Biofouling was also significantly associated with the types of substrata. The three chemicals used. namely antifouling paint, formulated bis-tributyltin oxide and tannin extract effected various degrees of suppression on fouling. The effects of bis-tributyltin oxide was similar to that of antifouling paint in suppressing most of the 13 foulers studied except mobile molluscs. But the degree of suppression by the former was milder as measured by the mean weight of the foulers at 42.3 g against 20.1 g of the latter. Tannin extract was least effective and suppression was only restricted to a few groups such as sea anemones, serpulid polychaetes, bryozoans and sessile molluscs.