Abstract.We have investigated the effect of a salmon farm on the local benthos and the benthic environment. The bottom fauna was examined before establishment in March 1988, during operation in September 1989 and April 1990, and after closure in March‐April 1991. During this time 2417 tonnes of salmon were produced. The samples were collected from two stations within 250m of the farm site. The sediment contained mainly clay and silt, the organic content varied from 9·1 to 17·3% and there was no increase in the organic content during the sampling period.The bottom fauna in 1988 was rich and relatively similar at both stations. The species number close to the farm declined from 65 in 1988 to only 11 in 1989. A year after the fish farm was moved, the number of species had risen to 29.The fish farm clearly influenced the bottom fauna in the immediate vicinity of the site but no effect was found at 250 m distance. The environmental conditions had improved in 1991 after abandonment of the site, but the fauna had not returned to the status measured before operations began in 1