Muckle Flugga lighthouse, north of Unst in the Shetland Islands

© George Slesser, Marine Scotland Science

The Scottish Continental Shelf includes the western coasts of the Outer Hebrides, Orkney and the western coast of Shetland and the northern coast of mainland Scotland. Typical water depths are between 100 m and 150 m and some areas become stratified in summer. The coastline is predominantly rocky. The main offshore habitats are expanses of mud, sand and coarse sediment. There are large seasonal variations in sea-surface temperature, ranging from 6 °C in winter up to 14 °C in summer.

Climate change

Sea level is rising but is not a significant issue in this region because of the generally rocky coastline. There is some evidence that rising sea temperature is leading to an extension of the northern limits of some warm-water seabed invertebrates.

Maritime economy

This region contains some of the most remote fishing communities in the UK, and the coasts support a range of inshore fisheries for shellfish and fin-fish including the most valuable UK towed-gear fisheries for demersal fish and Nephrops. Potting for edible crab is also now widespread. This region is the most valuable in the UK for marine fin-fish aquaculture. There are some important hydrocarbon fields in the Scottish Continental Shelf region and there was increased activity in exploration and appraisal drilling in 2007. Production has not yet started. Marine wildlife watching is a particularly important source of income in Northern Scotland and the Western Isles, Orkney and Shetland. The region is also important for leisure diving (e.g. Scapa Flow, Orkney) and a number of other coastal tourism activities including an annual surf championship.

Fishing pressure

Assessed commercial fish stocks are either not at full reproductive capacity or are not being harvested sustainably. With the exception of saithe and one haddock stock, there is some indication of improvement in the demersal fish community in the south-west of the region but no obvious trend in the north-west despite a reduction in fishing effort. Mobile fishing gears have damaged the sedimentary habitats with particular concern for the recovery of large slow-growing and fragile species of seabed invertebrate, including damage to cold-water coral reefs. Fishing may add to the pressure on seals although the reason for the decline in harbour seal numbers is not known.

Other issues affecting status

Seabird breeding numbers have declined. Breeding success has been lower than in any other UK region and particularly poor in Shetland. A shortage of food species has been associated with the declining numbers and a combination of fishing and rising sea temperature may be the cause of the reduced food supply but we do not have a good understanding of these interactions.

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