ABSTRACT. – The aquaculture industry is developing at a fast pace, growing from 1 million tonnes a year harvested in the 1950s, to more than 75 million tonnes nowadays. However, there are rising concerns over the environment impacts. The aim of this study is to investigate the impacts of salmon aquaculture in Loch Creran, Scotland, using mussels Mytilus edulis (Linnaeus, 1758) as a bioindicator. Water samples and mussel tissues were collected from two different sites along the loch shore and were analysed for contaminant bioaccumulation and biological effects, using gas chromatography and histology techniques. The results showed high levels of heavy metals and organic compounds (n-hexadecanoic acid, 1-Heptatriacontanol, Isophorone, Cholestan-3-ol and oleic acid) in mussel tissues close to the salmon farms. The histology results indicate that the mussels from the aquaculture site are in poor health condition, with 90 % of tissue samples exhibiting one or more signs of pollutant induced stress, such as haemocyte infiltrations, lipofuscin accumulation, parasites and possible neoplasms.