Seasonal Variations in Biofouling and Plankton Community Connected to a Large Scale Salmon Farm.
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- Institutt for biologi 
Biofouling is the one of the main problems in marine finfish aquaculture. Biofouling occludes the nets and incurs major costs to fish farmers in the form of copper containing anti fouling paints used on the net surfaces, cleaning and changing of nets. Copper containing anti fouling paints is the major protective method in use by the fish farmers, but given the toxicity of the copper towards the marine invertebrates and its ability to accumulate in the food chain, it may face a ban in marine aquaculture. So, there is a need to develop better anti fouling methods which will be as effective as copper, have least impact on the environment and cost effective to use. To design these, better understanding of the process of biofouling is needed. There is little data available about the biofouling in marine aquaculture.In this regard, I studied biofouling in a marine cage aquaculture farm (ACE/Tristeinen), located in mid-Norwegian coastal waters. In this study, knot less nylon net panels and Micanti net panels were used to compare different aspects of biofouling and to test the effectiveness of the Micanti nets. Zooplankton samples were collected and analyzed with a focus on the larval stages of the fouling organisms, to relate the plakntonic stages of the foulers in the zooplankton sample to the foulers present on the net panels. Sea lice larval stages presence in the zooplankton samples was also detected to study the movement of sea lice larval stages.Analysis of the net panels and zooplankton samples together showed a trend between the larvae of foulers found in the zooplankton samples and foulers present on the net panels. On net panels hydroids, mussels, algae, amphipods and nudibranchs accounted for the major proportion of the fouling. On nylon net panels hydroids were more compared to mussels and on Micanti net panels mussels were more compared to hydroids. Nets occlusion and net fouling wet weight was slightly less on the micanti net panels compared to nylon net panels. Few sea lice, Lepeophtheirus salmonis larval stages were found in the zooplankton samples. Micanti did not work as expected, as it having problems with strength, length and density of the fibers flocked on the net. Improving these would help to improve the functionality of the Micanti nets as a better non-toxic antifouling technology.