habitat_narrative
Marine
Although usually moving in small schools of between three and eight individuals (often segregated by age and sex), Sei Whales congregate at feeding grounds and may develop aggregations of more than 100 individuals. The blow shape of Sei Whales is similar to that of the Fin Whale, but does not project as high or as broadly. In comparison to that of the Fin Whale, the dorsal fin of the Sei Whale is more upright. Sei Whales are also considered fast swimmers, and have been recorded to reach speeds of up to 30 knots over short distances.Their diet is greater in variety than that of the Blue Whale, but they usually only feed on one food type at a time. For example, 21,713 North Pacific Sei Whale stomachs were dissected, revealing that 82.7% consisted only of copepods and the stomach contents of 12.6% comprised only of euphausiids; while in the southern hemisphere, 31,494 stomachs were examined, revealing that 54.3% contained only euphausiids, 30.5% consisted only of copepods and 14.4% of the dissected stomachs held only amphipods (Nemoto and Kawamura 1977). In the southern hemisphere, their most important prey is considered to be copepods, but in Antarctica specifically, they may take krill (Euphausia superba). Within the waters surrounding the assessment region, Sei Whales consume both euphausiids and copepods, however in small quantities (Bannister and Baker 1967, Best 1967). Sei Whales do not consistently return to the same feeding grounds every year, and may inexplicably disappear from a particular site during certain years, or even decades (Horwood 1987).
Breeding in the southern hemisphere usually takes place between the months of April and August, with a peak in June. The gestation period lasts for approximately 12 months. Newly born calves are usually about 4.5 m, and over the next six months grow rapidly to a length of approximately 8.0 m (Skinner and Chimimba 2005).
Ecosystem and cultural services: Marine mammals integrate and reflect ecological variation across large spatial and long temporal scales, and therefore they are prime sentinels of marine ecosystem change; migratory mysticete whales may be used to investigate broadscale shifts in ecosystems (Moore 2008).
