Information on the distribution, abundance, status and ecology of cetaceans in the eastern North Atlantic, and especially the area between Shetland and the Faroes, is limited. Data relevant to this review originates from several sources including:

1. Historical whaling records from whaling operation which existed in Shetland, the Hebrides and Ireland at the beginning of this century (Thompson 1928) (Brown 1976), and from whaling records from Norway and the Faroes
2. Records of stranded cetaceans from around the British coast (Sheldrick 1976) (Sheldrick 1989)
3. Sightings:
   
   1. from dedicated surveys such as those in Norwegian, Icelandic and adjacent waters (NASS-87, NASS-89), and SCANS survey of the North Sea and adjacent waters (Hammond et. al. 1995)
   2. from incidental sightings databases including JNCC and UK Mammal Society/SeaWatch (Northridge et. al. 1995) (Bloor et. al. 1996) (Evans 1976) (Evans 1980) (Evans et. al. 1986) (Evans 1992).

The coverage of these schemes and surveys is patchy both temporally and spatially, due to the scattered distribution of observers (in space and time); changes in the probability of sighting cetaceans under different sea conditions; and, low survey effort in certain areas (such as the area of interest, west of Shetland). The waters west of Shetland have received very little survey effort (prior to investigations as a result of recent developments there). Nevertheless, these data give an idea of which species occur in these waters. It is important to consider the broad region as a whole, particularly in view of the long migrations and seasonal movements undertaken by some species and the current uncertainty about stock boundaries and status (Christensen et. al. 1992). Information on the distribution of cetaceans around the UK and Ireland may be found in Evans (1980), Evans et. al. (1986), Evans (1992), Evans and Scanlan (1989), Sheldrick (1989), Northridge et. al. (1995), Hammond et. al. (1995).

The bottom topography of the area to the west of Britain and Ireland is complicated (see fig. 1). The continental shelf edge dominates this, running in an approximately north-east to south-west direction. The shelf slopes steeply, dropping to depths of several thousand metres, less than 100 nautical miles from land. In basins such as the South Iceland Basin, Norway Basin and Rockall Trough the depth is over 4,000 m in places. To the west of Shetland, the Faroe-Shetland channel divides the Faroe shelf from the West Shetland shelf. To the south of the Faroes, the Wyville-Thomson Ridge forms the head of the Rockall Trough. At the northern end of the Rockall Trough are two seamounts, and to the west is the Rockall Plateau. The area is characterised by a series of deep channels and basins, shallow platforms, ridges and seamounts with steeply shelving edges.

1.2 Whaling in Scotland and Ireland

Modern whaling (using explosive harpoons fired from a steam powered catcher boat to capture the fast swimming rorqual whales) began from shore stations in Norway in the 1860's, and spread to the Faroe Islands, Iceland and Spitsbergen and finally the British Isles in 1903. There were four whaling stations in the Shetland Islands: two in Ronas Voe on the north-west coast of the mainland which opened in 1903, one in Colla Forth, Yell Sound and one in Olna Firth (west coast of the mainland) both opened in 1904. A station opened in the Outer Hebrides on Harris at Bunaveneader, West Loch Tarbert in 1904, and two in Ireland (one on South Iniskea, north-west County Mayo which opened in 1908 and one at Ardelly Point, County Mayo from 1910).

Fin whales were the main species caught, but blue, humpback, sei, right, sperm and bottlenose whales were also hunted. Following closure during World War I, four whaling stations re-opened in 1920, but whaling ended in 1929. The Hebridean operation worked for an additional two seasons in 1950-51.

The composition of the catches were similar at the Hebridean station and the Irish stations, but differed from the Shetland stations, where few blue whales and right whales were caught. Whaling generally occurred between April and September each year. Whaling grounds extended in an arc northwards from west to east of the islands as far as 150 nautical miles from the stations (see fig. 2). In the years between 1903-1914 and 1920-1929 the whaling stations in Shetland caught a total of 6,830 whales (the majority almost 70% were fin whales, over 20 % were sei whales and small numbers of blue, sperm, right, humpback and bottlenose whales). In the Hebrides, the whaling grounds extended in a westward arc from south to north to about 180 miles from the station on Harris. The catch here was also dominated by fin and sei whales but much higher numbers of blue whales and greater numbers of sperm and right whales were killed. Thompson (1928) and Brown (1976) present further details on total species catches.

Whaling elsewhere in the North-east Atlantic.
Whaling occurred off western Norway between 1918 and 1939, in Iceland until 1915 and again in 1935-1939. It also occurred in the Faroe Islands between 1920-1930 and 1933-1939. Factory ships also began working pelagic waters in the early 1930's, mainly between Spitsbergen, Iceland and the Denmark Strait (Brown 1976).

1.3 Surveys

There have been several cetacean sighting surveys in the North Atlantic. They have generally concentrated on areas away from the European continental shelf around Iceland and Norway, bordering and in some cases including the area west of Shetland. North Atlantic Sightings Surveys, NASS-87 and NASS-89 surveys were conducted by Icelandic, Faroese and Norwegian vessels. NASS-87 was conducted in June and July in Icelandic and adjacent waters. It included three survey blocks off Britain, one west of the Hebrides and Ireland, one around the Faroes and one north, north-east and north-west of Shetland (Sigurjonsson et. al. 1989) (Gunnlaugsson and Sigurjonsson 1990). NASS-89 surveys covered waters mainly south and south-west of Iceland, but included the Rockall Plateau west of the British Isles (Sigurjonsson et. al. 1991). Surveys were conducted off Norway and adjacent waters during the summers of 1987-88 (Oien 1989, 1990, 1991). These surveys were all targeted primarily at obtaining abundance estimates for commercially valuable species, but small cetaceans were also recorded (e.g. Buckland et. al. 1993).

In contrast to the large (commercially important) whales, knowledge of the smaller toothed whales is rather superficial. Surveys of small cetaceans in the North-east Atlantic have mostly been localised or short term, often concentrating on coastal waters. Knowledge of the cetacean fauna of the area is therefore limited, but some inferences can be drawn from existing information. The main target of many of these surveys is the minke whale, but other species have also been recorded systematically.

The SCANS survey (Small Cetacean Abundance in the North Sea and adjacent waters) examined the distribution and abundance of the harbour porpoise and other small cetaceans in the North Sea and adjacent areas. The survey area was determined initially by reference to the areas covered by ASCOBANS. This included waters around Shetland and Orkney (Hammond et. al. 1995).

Peter Evans (Sea Watch Foundation) has conducted surveys in coastal waters of the Hebrides and Shetland Isles, e.g. (Evans et. al. 1993) (Evans 1995). He also runs a sightings network through the UK Mammal Societies Cetacean Group.

Reported strandings are collated and analysed by the Natural History Museum (Sheldrick 1976, 1989). This has been under contract to the Department of the Environment since 1990.

The Joint Nature Conservation Committee (JNCC) collect cetaceans sightings as part of the work of the 'Sea Birds at Sea' Team. The data from the SAST database is available on UKDMAP digitised maps, and in publications such as Northridge et. al. (1995) and Bloor et. al. (1996).

A research project, utilising the US Navy/Royal Navy Integrated Undersea Surveillance System to detect the presence of the larger (blue, fin, humpback and minke) whales in the Atlantic Frontier region, managed by the JNCC and conducted by Cornell University is currently underway. Although there are no formal results from this project yet, some newspaper articles recently appeared in the press based on this research.