The seas around Scotland support a wide variety of fish species, some of which have been a source of livelihood, food and culture for centuries. Different components of the fish community have been assessed using different parameters. The Wider fish community assessment is based on 167 different species sampled by the International Bottom Trawl Survey designed to assess changes in demersal (bottom dwelling) fish communities. This includes a range of both commercial and non-commercial species. The Commercial fish assessment is based on the status of the eight species of greatest commercial value to Scotland (mackerel, herring, haddock, monkfish, cod, hake, whiting, saithe) using fishery and survey data. The Inshore fish (estuaries and reduced salinity sea lochs) is undertaken to determine the quality of transitional waters and the assessment is based on six representative inshore sites on the east and west coasts of Scotland. The Deep sea fish assessment is based on data from various scientific trawl surveys that provide a measure of species richness. Scotland has long been renowned for its Salmon and sea trout – two species that spend part of their life cycle at sea before returning to their natal river to spawn. The assessment of these stocks is based on returning fish (catches and count data) for 173 assessment areas which are primarily single river catchments. Altogether these various assessments provide an overview of the status of the different fish stocks, but much remains to be done to fully understand their behaviour and dynamics. The Case study: Basking sharks in Scottish waters for example describes how the use of cutting-edge technologies has greatly increased our understanding of the distribution, migration and behaviour of the basking shark (the second largest fish in the ocean) that frequent the waters off the west coast of Scotland. Similarly, the Case Study: Flapper skate – Loch Sunart to the Sound of Jura MPA describes how a capture-tag-recapture project involving recreational sea anglers, data storage tags and acoustic arrays have greatly improved our understanding of the ecology of the skate and consequently informed the necessary management measures needed to ensure their protection. The Case study: Sandeels in Scottish waters describes this fish stock that is an important component of the food web.