MICROFOULING OF SALMON-CAGE NETTING - A PRELIMINARY INVESTIGATION

Microfouling development on salmon-cage netting in Tasmania, Australia , was studied by scanning electron microscopy (SEM). Temporal changes and distribution of the fouling microorganisms were documented for the horizontal netting bars in winter and spring. Diatoms were dominant o n the upper surfaces of the netting bars and protista on the lower sur faces. This distribution is considered to be a consequence of shading of the lower surfaces from light and the abundance of protista is attr ibuted to high nutrient levels associated with the dense fish populati on. With increasing immersion time, there was a progression in diatom communities from prostrate forms to large erect and stalked forms in w inter, and tube-dwelling forms in spring. Both the rates and the depth of fouling varied between seasons. Copper-based and silicone-based an tifoulants effectively delayed fouling development. The former also se lected for diatom species known to be copper-tolerant. In contrast, th e silicone-treated netting was colonised mostly by the same species as the untreated netting.