ENVIRONMENTAL EFFECTS OF FLOATING FISH CAGES IN THE SETIU ESTUARY/LAGOON OF TERENGGANU, MALAYSIA

In order to address the environmental effects of floating fish farms in the Setiu estuary/lagoon of northeast peninsular Malaysia, foraminifera, sediment grain-size, and carbon and nitrogen isotopic ratios have been analyzed in surface samples in and around the three floating fish cage complexes. Two currently functional floating fish cage complexes, SET11-S43 and SET11-S40, in a lagoon close to an inlet (salinity in the 20s) have mixed agglutinated and calcareous assemblages with the majority of live foraminifera at these sites being calcareous species. At an abandoned fish cage complex, SET11-S9A, located in a low salinity (<5) estuarine setting, Miliammina fusca and Ammobaculites exiguus dominate entirely agglutinated assemblages. Side scan sonar data as well as grain-size analysis of surface sediment samples surrounding the fish cage complexes indicate that a muddy substrate extends up to 10s of meters from the cages with a surrounding sandier substrate typical of most of the Setiu estuary/lagoon system. The percent of carbon and nitrogen in sediment exhibit distributional patterns that correlate with the distribution of the fish cage mud. Greater abundance of carbon and nitrogen in sediment is found to the north of the active fish cage complexes, SET11-S43 and SET11-S40, than to the south. High carbon and nitrogen abundance also characterizes samples taken within the fish cage complexes at SET11-S43 and SET11-S9A but not at SET11-S40. These patterns are attributed to organic matter input from both fish farms and the surrounding mangrove forest, as well as tidal currents.