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Seals and Sirenia
The pinniped nomenclature used here is based on Rice (1998), who subsumes the former order Pinnipedia within the Carnivora. The two families are the true seals (Phocoidae) and the eared seals, i.e. fur seals, sea lions and walruses (Otariidae). Morphologically they are very close, due to their adaptation to the marine environment, and this similarity extends to their migratory behaviour, which is summarised here.

In general, the pinnipeds are found around the cooler ocean currents, with the 20° C isotherm as a limit. Exceptions are the monk seals, Monachus spp., inhabiting tropical and subtropical waters. Two land-locked species, Pusa caspica and Pusa sibirica, inhabit the Caspian Sea and Lake Baikal.

All species are amphibious. Parturition and moulting occurs on land, while virtually all feeding is restricted to their aquatic habitat. Seasonal migrations are closely correlated with the requirements of feeding and breeding behaviour. Nutrient-rich marine areas are preferred for feeding, while oceanic islands, rocky shores or ice are preferred for breeding. Migration behaviour is very complex, and males, females and juveniles exhibit different return migrations in accordance with their biological needs. The best overview for the whole group is still the compilation by Baker (1978), who tabulated migration distances for males, females and juveniles for most species (l.c., p. 718). Migratory status within GROMS is based on these data, which still had many question marks. Meanwhile, satellite data and genetic analysis provide detailed data sets for certain individuals and populations, but there are still considerable knowledge gaps, in particular for the rare species. Major satellite studies concentrate on grey seals (Halichoerus grypus: Sjoberg et al. 1999) and harbour seals (Phoca vitulina). Population genetic studies reveal valuable insights, and Gemmel et al. (1997) have identified DNA markers for 18 pinniped species. These techniques have been used by Burg et al. (1999) for an investigation of the genetic diversity and population structure of harbour seals (Phoca vitulina richardsi) along the coasts of British Columbia and parts of Alaska (see Figure A2.16).

One species and a subspecies have become extinct. There have been no documented reports of the Japanese sea lion (Zalophus californianus japonicus) since the late 1950s. The Caribbean monk seal (Monachus tropicalis) was last seen at Seranilla Bank in 1952. Aerial surveys in 1973 through the Gulf of Mexico and around the Yucatan Peninsula failed to find any surviving individuals the species is definitely extinct (Hilton-Taylor 2000). Its close relatives, the Hawaiian and the Mediterranean monk seals, are both threatened, with the latter (Monachus monachus) on the brink of extinction for a variety of reasons (Figure A2.17). One major threat affecting practically all species is entanglement in fishing gear and abandoned nets (‘ghost fishing’). At least 15 of the world’s 32 pinniped species have been seen entangled. This kills thousands of northern fur seals in Alaska (GESAMP 1990), and is a severe threat to the above-mentioned monk seals (Veryeri et al. 2001).

Seals are often considered as competitors by fishermen, which leads to illegal hunting or legal culling. The latter is still viewed as a management tool to reduce seal populations considered too abundant. The expected effect is an increase in fish populations. However, the underlying models of predator-prey interactions are probably too simplistic, and Yodzis (2001) showed conclusively that adverse effects can occur in more complex food webs: Seals do not only feed on target fish species, but also on other predators. Therefore, culling of seals might lead to an increase in predatory fish. However, it is difficult to prove any model experimentally, due to the considerable time lags of population data and the complexity and vast extension of the respective ecosystems.

Due to the interaction with fisheries, the national legal status of most species of seals is complex. Hunting has been reduced considerably, and in some parts has been reduced to subsistence hunting for aborigines.31

Most species are protected at least regionally or seasonally. However, there are temporary exceptions or tolerated infringements sanctioned by custom. Finally, incidental mortality as bycatch is not prosecuted, even for highly endangered species such as the monk seal (Veryeri et al. 2001).

Populations of two species are listed in CMS Appendix II, while the critically endangered monk seal ranks on CMS Appendices I and II (Table 4.4)

Tab. 4.4: Threatened migratory seal species and subspecies. Note that there are several insufficiently known or threatened species which might be a focus of future conservation measures under the CMS. Tab. 4.4: Bedrohte wandernde Seehundarten und -unterarten. Man beachte, daß mehrere Arten unzureichend erforscht oder bedroht sind. Diese Tiere stellen einen möglichen zukünftigen Schwerpunkt bei Erhaltungsmaßnahmen durch die Bonner Konvention dar.
Species Common name Red List 2000 Migration CMS Status
Arctocephalus philippi Juan Fernandez fur seal VU Partial
(foraging females)
Callorhinus ursinus Alaskan fur seal VU Long distance
Halichoerus grypus grypus Grey seal -
Northeast Atlantic
EN partial NL
Halichoerus grypus macrorhynchus Grey seal -
Baltic Sea populations
NL partial App. II
Eumetopias jubatus Northern sea lion EN partial (males long distance) NL
Monachus monachus Mediterranean monk seal CR range extension App. I & II
Phoca caspica Caspian seal VU intraoceanic NL
Phoca vitulina Common seal DD Bering:
Phoca vitulina vitulina Common seal - only Baltic and Wadden Sea populations DD   App. II (Pop)
Pusa hispida Ringed seal EN partial; Bering:

31 for population numbers and quotas see "Marine Hunters: Whaling and Sealing in the North Atlantic", published by the High North Alliance, 1997
Mammals < Marine mammals > Birds
Seals & sirenia
Manatees & dugongs
Whales & dolphins

This document should be quoted as part of the publication "Riede, K. (2001): The Global Register of Migratory Species ­ Database, GIS Maps and Threat Analysis. Münster (Landwirtschaftsverlag), 400 pp." + CD

 by Klaus Riede