Fin whale  (Balaenoptera physalus)

Fin whales are the fastest of all cetaceans, reaching speeds of 37 kilometres per hour and known to completely clear the water. This whale is grey in colour on the upper surface and white on the underside (4). The patterns on the jaw are asymmetrical, being white on the right side and dark on the left, and a large number of grooves extend along the throat to the naval (4). The prominent dorsal fin is 60 centimetres in length and curves strongly (4). Males and females tend to be very similar in their general appearance, but females are slightly longer than males (4). The baleen plates are bluish to grey in colour and have white fringes (2).

This species has a global distribution but is quite rare in tropical or iced polar seas. It occurs in the Atlantic, Pacific, Indian and Arctic Oceans (5); the species is split into two subspecies which do not appear to come into contact, one in the south (B. p. quoyi) and one in the north (B. p. physalus) (5). The fin whale is the only rorqual commonly found in the Mediterranean (6).

A pelagic and coastal species, sometimes occurring in water as shallow as 30 meters (5).

Fin whales tend to occur in pairs or in groups known as pods that usually contain around six or seven individuals; although larger groups have been observed (5) (7). This species spends spring and early summer in cold feeding grounds at high latitudes, migrating to more southerly areas for winter and the breeding season (5). Northern and southern populations never meet because the seasonal patterns are reversed in the two hemispheres, and so they migrate to the equator at different times of year (5). Mating takes place in winter, and as gestation takes about 11 months, births occur in the winter breeding grounds where conception took place (5). A single calf is produced, which is suckled for six to seven months; when weaned, calves travel with their mother to the feeding grounds (5). Females produce calves every couple of years after reaching sexual maturity at three to twelve years of age. Full maturity is usually attained at 25 to 30 years of age (5).

Fin whales feed by filtering planktonic crustaceans, fish and squid through their baleen plates. Individuals can dive to depths of 230 metres and can stay submerged for about 15 minutes (7) (8). The blow of a fin whale reaches six metres in height and is a slim cone shape (7).

The major threat to the survival of this species has been hunting; their blubber, oil and baleen were all highly prized (4). Between 1935 and 1965, over 30,000 individuals were killed every year (7). At present, there is evidence of man-made injuries to fin whales, many of which have resulted from collisions with boats (9). Like other large whales, they are also threatened by environmental change, including noise and chemical pollution (10).

In 1985, the International Whaling Commission (IWC) banned the hunting of all whales by signatory states. The IWC regulates the International Convention for the Regulation of Whaling (1946), and also provides scientific advice to signatory states (11). Conservationists are worried however, that these protection measures are a case of 'too little too late', the southern hemisphere is thought to support only 5,000 fin whales, and the northern seas hold just 2 to 3,000 individuals (4). It seems likely that the species may never recover from past over-exploitation.

For more information on whales and dolphins and their conservation see:

• The Whale and Dolphin Conservation Society (WDCS):
  www.wdcs.org/
• The Smithsonian Institution's North American Mammals website:
  www.mnh.si.edu/mna/

Authenticated (8/10/02) by WDCS, the Whale and Dolphin Conservation Society.
http://www.wdcs.org