Sei Whale - Range and Migration

Range and Migration

Sei whales live in all oceans, although rarely in polar or tropical waters. The difficulty of distinguishing them at sea from their close relatives, Bryde's whales and in some cases from fin whales, creates confusion about their range and population, especially in warmer waters where Bryde's whales are most common.

In the North Atlantic, its range extends from southern Europe or northwestern Africa to Norway, and from the southern United States to Greenland. The southernmost confirmed records are strandings along the northern Gulf of Mexico and in the Greater Antilles. Throughout its range, the whale tends to avoid semi-enclosed bodies of water, such as the Gulf of Mexico, the Gulf of Saint Lawrence, Hudson Bay, the North Sea, and the Mediterranean Sea. It occurs predominantly in deep water, occurring most commonly over the continental slope, in basins situated between banks, or submarine canyon areas.

In the North Pacific, it ranges from 20°N to 23°N latitude in the winter, and from 35°N to 50°N latitude in the summer. Approximately 75% of the North Pacific population lives east of the International Date Line, but there is little information regarding the North Pacific distribution. Two whales tagged in deep waters off California were later recaptured off Washington and British Columbia, revealing a possible link between these areas, but the lack of other tag recovery data makes these two cases inconclusive. In the Southern Hemisphere, summer distribution based upon historic catch data is between 40°S and 50°S latitude in the South Atlantic and southern Indian Oceans and 45°S and 60°S in the South Pacific, while winter distribution is poorly known, with former winter whaling grounds being located off northeastern Brazil (7° S) and Peru (6° S). The majority of the "sei" whales caught off Angola and Congo, as well as other nearby areas in equatorial West Africa, are thought to have been predominately misidentified Bryde’s whales. For example, Ruud (1952) found that 42 of the "sei whale" catch off Gabon in 1952 were actually Bryde's whales, based on examination of their baleen plates. The only confirmed historical record is the capture of a 14 m (46 ft) female, which was brought to the Cap Lopez whaling station in Gabon in September 1950. During cetacean sighting surveys off Angola between 2003 and 2006, only a single confirmed sighting of two individuals was made in August 2004, compared to 19 sightings of Bryde's whales.