Marine mammals

Marine mammals

5-Marine_mammals-(P)-Pod_of_pilot_whales--(copyright-Gudmundur_St_V)

A pod of pilot whales in the open ocean

Photo: Guðmundur St. Valdimarsson

5-Marine_mammals-(P)-Humpback_whale_breaching--(copyright-Tryggvi_S)

Humpback whale breaching in Steingrimsfjordur, Northwest Iceland

Photo: Tryggvi Sveinsson

Marine mammals are the top predators and the largest consumers in Arctic and subarctic environments. The majority of seal species live in cold environments and many of these species are among the most abundant large mammals on earth. Whale species are more evenly spread over the world, but most of the large species depend on abundant food supply in high latitudes in summer. Many migrate to warmer waters in the winter when food is harder to get in the colder ecosystems. This is also the case with many seabirds. Their ability to fly makes them able to escape the harsh northern winters but enjoy the rich food supply in these environments in the summer. The warm internal temperatures and high metabolic rate combined with large biomass of the whales make the marine mammals and the birds the top predators of the Arctic and subarctic environment.

At least 12 species of cetaceans occur regularly in Icelandic waters, 5 species of baleen whales and 7 species of toothed whales, including dolphins and porpoise. In addition, 11 species have been recorded more sporadically. Whaling has been conducted in Icelandic waters throughout the centuries and research on the whale stocks around Iceland is therefore considered important. Reliable abundance estimates exist for most species of large whales while such estimates are not available for small cetaceans. In the continental shelf area, common minke whales probably have the largest biomass while on the open ocean it is the fin whales.

Seals are also fairly common in Icelandic waters. However, further north in the high Arctic they are even more abundant. This is also where the most numerous seal species go to breed on the sea ice. Only two species of seals are really native to Iceland, neither of which leaves coastal waters. However five other species from the north visit Iceland on a regular basis.

The third group of marine mammals occurring in Iceland consists of only one species, the polar bear (Ursus maritimus). Polar bears feed almost exclusively on ice-associated seals. Most of their life is therefore spent on drift ice in the ocean; hence they are classified as marine mammals. Adult polar bears are also quite good swimmers if required. Polar bears are not native to Iceland but are frequent guests, especially in cold years associated with drift ice. Exceptions do also occur; for example two visited Iceland in the summer 2008 in a rather warm year with no drift ice in sight. During the 20th century about 50 polar bear visits were recorded.

It should also be mentioned here for completeness sake that one species of marine reptile has been spotted in Icelandic waters. This is the leatherback turtle (Dermochelys coriacea), the largest of the sea turtles and the species that can live in the coldest waters since it is able to maintain relatively high internal temperatures. It has both been sighted alive in the ocean and found stranded dead. However, this is very rare since Icelandic waters are much too cold for this beast to occur on a regular basis. There are no records of marine turtles having been caught in any type of fishing gear in Icelandic waters. Hence devices to avoid turtle bycatch in Icelandic shrimp fisheries are totally unnecessary.

References and further information

  • Haraldsson, T., & Hersteinsson, P. (2004). Hvítabjörn (Polar bear). In Hersteinsson, P. (ed.), Íslensk spendýr (Icelandic mammals) (pp. 102-107). Reykjavík, Iceland: Helgafell.
  • Sigurjónsson, J., & Víkingsson, G. A. (1997). Seasonal abundance of and estimated food consumption by cetaceans in Icelandic and adjacent waters. J. Northwest Atl. Fish. Sci. 22, 271-287.
  • Stefánsson, G., Sigurjónsson, J., & Víkingsson, G. A. (1997). On dynamic interactions between some fish resources and cetaceans off Iceland based on a simulation model. J. Northwest Atl. Fish. Sci. 22, 357-370
  • .Ægisson, S., Ásgeirsson, J., & Hlíðberg, J. (1997). Icelandic whales - past and present. Reykjavik, Iceland: Forlagid, 96 pp

Hreiðar Þór Valtýsson, University of Akureyri