This report is a contribution to the Strategic Environmental Assessment (SEA3) conducted by the Department of Trade and Industry (now Department of Energy and Climate Change) and is an addendum to "SEA2 Technical report 005 - An overview of plankton ecology in the North Sea" by same authors. Eight marine mammal species occur regularly over large parts the North Sea: harbour seal, grey seal, harbour porpoise, bottlenose dolphin, white-beaked dolphin, Atlantic white-sided dolphin, killer whale and minke whale. A further 15 cetacean species and five pinniped species are reported less frequently in the region. This report describes the distribution and abundance of these mammals and their ecological importance. The harbour porpoise the most numerous marine mammal in the North Sea, with a population estimated at 268,000 in summer 1994. The northern parts of the SEA3 area are important for the three most abundant cetacean species in the North Sea: minke whale, harbour porpoise and white-beaked dolphin. Harbour seals occur widely in the SEA3 area. Marine mammals make use of sound for a variety of purposes: finding prey, detecting predators, communication and probably navigation. The offshore oil and gas industry generates underwater noise at every stage of the process: during exploration seismic surveys, drilling, production and decommissioning. The effects of these different sources of underwater noise on marine mammals are discussed. The use of explosives for underwater cutting and demolition during the decommissioning of platforms and installations may pose a serious threat to some marine mammals. The effects of pollution on seals and cetaceans are discussed, including the effects of oil spills. Large whales can be killed by being struck by ships; increased shipping traffic in an area would increase this threat.

This report is a contribution to the Strategic Environmental Assessment (SEA4) conducted by the Department of Trade and Industry (now Department of Energy and Climate Change). Twelve marine mammal species occur regularly in the SEA4 area: grey seal, harbour seal, hooded seal, harbour porpoise, white-beaked dolphin, Atlantic white-sided dolphin, Risso's dolphin, long-finned pilot whale, killer whale, minke whale, fin whale and sperm whale. A further eleven cetacean species and four pinniped species are occasional visitors. This report describes the distribution and abundance of these mammals and their ecological importance. The SEA4 area is an important area for cetaceans, but little is known about the abundance or seasonal distribution of many species. Marine mammals make use of sound for a variety of purposes: finding prey, detecting predators, communication and probably navigation. The offshore oil and gas industry generates underwater noise at every stage of the process: during exploration seismic surveys, drilling, production and decommissioning. The effects of these different sources of underwater noise on marine mammals are discussed. The use of explosives for underwater cutting and demolition during the decommissioning of platforms and installations may pose a serious threat to some marine mammals. However, current understanding of the effects of noise on marine mammals is rudimentary. The effects of pollution on seals and cetaceans are discussed, including the effects of oil spills. The diseases to which they are subject are briefly discussed, as are non-oil management issues such as fisheries bycatch.

This report is a contribution to the Strategic Environmental Assessment (SEA7) conducted by the Department of Trade and Industry (now Department of Energy and Climate Change). Twenty-one cetacean species have been recorded in the SEA7 region. Of these, ten species are known to occur regularly: harbour porpoise, bottlenose dolphin, short-beaked common dolphin, Risso's dolphin, white-beaked dolphin, Atlantic white-sided dolphin, long-finned pilot whale, killer whale, sperm whale and minke whale. Five further species, though not very often recorded, and primarily associated with deep water, probably also occur regularly: striped dolphins, fin whales, northern bottlenose whales, Cuvier's beaked whale and Sowerby's beaked whale. There are occasional at-sea records of a further 6 species: Sei whale, humpback whale, blue whale, northern right whale and false killer whale. Pygmy sperm whales and at least three further species of beaked whale might also be expected in the general area on occasion. In this report, each of the more abundant species is briefly described with particular reference to its distribution and abundance in the SEA-7 area.

This report is a contribution to the Strategic Environmental Assessment (SEA6) conducted by the Department of Trade and Industry (now Department of Energy and Climate Change). Seven marine mammal species are known to occur regularly in the SEA6 area. A relatively small but fairly discrete population of grey seals utilises all but the northwest Irish Sea. Harbour seals are found primarily in the far north of the area. Harbour porpoises are seen year round throughout the area and bottlenose dolphins are present year round off Wales. Minke whales, Risso's dolphins and short-beaked common dolphins are regularly seen in summer mainly in the far south. The report discusses the distribution and abundance of these mammals and their ecological importance. Marine mammals make use of sound for a variety of purposes: finding prey, detecting predators, communication and probably navigation. The offshore oil and gas industry generates underwater noise at every stage of the process: during exploration seismic surveys, drilling, production and decommissioning. The effects of these different sources of underwater noise on marine mammals are discussed. The use of explosives for underwater cutting and demolition during the decommissioning of platforms and installations may pose a serious threat to some marine mammals. The effects of pollution on seals and cetaceans are discussed, including the effects of oil spills. The prevalence of disease among the marine mammal populations is reviewed.

This report is a contribution to the Department of Trade and Industry's (now Department of Energy and Climate Change) Strategic Environmental Assessment SEA2. Eight marine mammal species occur regularly over large parts the North Sea: harbour seal, grey seal, harbour porpoise, bottlenose dolphin, white-beaked dolphin, Atlantic white-sided dolphin, killer whale and minke whale. A further 15 cetacean species and five pinniped species are reported less frequently in the region. This report describes the distribution and abundance of these mammals and their ecological importance. The harbour porpoise is the most numerous marine mammal in the North Sea, with a population estimated at 268,000 in summer 1994. The northern and central SEA2 areas are particularly important areas for the harbour porpoise. Marine mammals make use of sound for a variety of purposes: finding prey, detecting predators, communication and probably navigation. The offshore oil and gas industry generates underwater noise at every stage of the process: during exploration seismic surveys, drilling, production and decommissioning. The effects of these different sources of underwater noise on marine mammals are discussed. The use of explosives for underwater cutting and demolition during the decommissioning of platforms and installations may pose a serious threat to some marine mammals. The effects of pollution on seals and cetaceans are discussed, including the effects of oil spills. Large whales can be killed by being struck by ships; increased shipping traffic in an area would increase this threat.

This report is a contribution to the Strategic Environmental Assessment (SEA5) conducted by the Department of Trade and Industry (now Department of Energy and Climate Change). Eight marine mammal species are known to occur regularly in this area: grey seal, harbour seal, harbour porpoise, white-beaked dolphin, bottlenose dolphin, Atlantic white-sided dolphin, killer whale, and minke whale. Long-finned pilot whales and Risso's dolphins are regularly seen in waters around Shetland. There are occasional at-sea records of at least a further five cetacean species (humpback whale, fin whale, sperm whale, striped dolphin and short-beaked common dolphin) and four pinniped species (hooded seal, bearded seal, ringed seal and walrus).