Video assessment of environmental impacts of salmon farms

Video recordings have become a common method for monitoring the benthic environment around salmon farms, but generally they are only assessed qualitatively. We made a quantitative assessment of video recordings and compared the results with benthic invertebrate faunal data from the same sites. Transects around two Atlantic salmon (Salmo salar L.) farms were videoed, with environmental variables that clearly showed change with levels of organic enrichment ranked according to their degree of occurrence. These variables included Beggiatoa cover, pellets and faeces, sediment colour, and abundance of flora and fauna. Analysis of the data by multivariate statistics indicated that quantitative data from video recordings can clearly detect major organic enrichment, but that they are not as sensitive as benthic infaunal data to lower levels of disturbance. This assessment technique will need to be tailored to different environmental conditions, but shows promise for long-term monitoring programs.