Two species of seals are present year-round in coastal waters, harbour seal Phoca vitulina and grey seal Halichoerus grypus, with a further five pinniped species as infrequent visitors.
The abundance of harbour seals in central Norway has decreased since the late 1990s, mainly from hunting, but abundance is now increasing. Surveys of grey seals have shown a 50–60% reduction in pup production between 2007–2008 and 2014–2015 in mid-Norway, probably as a result of increased bycatches in gillnet fisheries for monkfish Lophius piscatorius and cod.
Twelve cetacean species are commonly observed in Norwegian waters, either on a year-round basis or as seasonal visitors in the productive summer season. The numbers of minke whales in the northeast Atlantic (including the Norwegian Sea) are stable overall (2007–2013). However, a general displacement of minke whales and other baleen whales towards the northeast implies a shift from the Norwegian Sea to the Barents Sea.