2Artificially created ecosystems (ACEs) in coastal waters: developing methods to assess their effects on wild fish in cold-waterenvironments

Artificial structures, such as marinas, harbours, sea-cage fish farms, mussel rafts and oil platforms, are widespread throughout Norway's coastal zone. Such structures may constitute 'Artificially Created Ecosystems' (ACEs) by providing substantial artifi cial habitat and modifying ecosystem processes in their vicinity. Sea-cage fish farms are one such example of widespread artificial structure in Norway's coastal zone and farms are increasing in both number and size. Over 1000 farms operate and release > 800 000 tons of fish food into coastal waters each year. Little is known of the effect of the artificial environment farms create on wild fish that aggregate in their immediate vicinity, principally due to a lack of appropriate techniques to census fish i n the unique 3-dimensional environment they create. We intend to adapt and test a variety of fish census techniques to suit the unique environment around sea-cage fish farms in Norwegian coastal waters, which are typically placed in deep, cold-waters with varying environmental conditions (e.g. visibility, current). Once developed, these techniques will be used to assess wild fish species diversity, abundance and biomass around 9 representative salmon farms along the Norwegian coast and 9 control locations to gauge the magnitude of aggregation at fish farms. We will also collect farm-associated wild fish and wild fish from control locations for analysis of biological parameters (size, sex, diet, condition, parasite loading) to determine the possible ecolog ical effects of aggregation to wild fish stocks. Combined, the information from censuses and biological sampling will provide baseline data that will assist managers to devise strategies to enhance the positive and minimise the negative environmental effe cts of artificial structures in coastal waters.