Fish catch data comprising species identification, abundance and length. Weight, sexual maturity and age are also recorded for a sub-sample of the total catch. The data were obtained from a number of sea lochs in the Forth of Lorne and the Isle of Mull, north west Scotland, typically on a monthly basis between 1969 and 1973. The data were obtained from fish caught by bottom and mid-water otter type trawls (including Seine, Agassiz and beam trawls). Collectively, these data form an unique insight into the fish population history of this region. The original data were collected under the overall supervision of John Gordon, at the Scottish Marine Biological Association (SMBA).