Interesting Creatures…The Sei whale (Balaenoptera borealis)

Jan 04, 2015 Features / Columnists, Interesting Creatures in Guyana

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The Sei whale, Balaenoptera borealis, is a baleen whale, the fourth-largest rorqual after the blue whale, the fin whale and the humpback whale. It inhabits most oceans and adjoining seas, and prefers deep offshore waters. It avoids polar and tropical waters and semi-enclosed bodies of water. The sei whale migrates annually from cool and sub-polar waters in summer to winter in temperate and subtropical waters.
Reaching 19.5 metres (64 ft) long and weighing as much as 28 tonnes (28 long tons; 31 short tons), the sei whale daily consumes an average of 900 kilograms (2,000 lb) of food, primarily copepods, krill, and other zoo plankton.
The sei whale feeds near the surface of the ocean, swimming on its side through swarms of prey.
For an animal of its size, for the most part, its preferred foods lie unusually relatively low in the food chain. The whale’s diet preferences have been determined from stomach analyses, direct observation of feeding behaviour, and analyzing fecal matter collected near them, which appears as a dilute brown cloud. The feces are collected in nets and DNA is separated, individually identified, and matched with known species.

The Sei whale competes for food against clupeid fish (herring and its relatives), basking sharks, and right whales. It is among the fastest of all cetaceans, and can reach speeds of up to 50 kilometres per hour (31 mph) (27 knots) over short distances.
Following large-scale commercial whaling during the late nineteenth and twentieth centuries, when over 255,000 whales were taken, the sei whale is now internationally protected, although limited hunting occurs under a controversial research programme conducted by Japan.
As of 2008, its worldwide population was about 80,000, nearly a third of its pre-whaling population.
Sei is the Norwegian word for pollock, also referred to as coalfish, a close relative of codfish. Sei whales appeared off the coast of Norway at the same time as the pollock, both coming to feed on the abundant plankton. The specific name is the Latin word borealis, meaning northern. In the Pacific, the whale has been called the Japan finner; “finner” was a common term used to refer to rorquals.
Sei whales are rorquals (family Balaenopteridae), baleen whales that include the humpback whale, the blue whale, the Bryde’s whale, the fin whale, and the minke whale. Rorquals take their name from the Norwegian word røyrkval, meaning “furrow whale”, because family members have a series of longitudinal pleats or grooves on the anterior half of their ventral surface. Balaenopterids diverged from the other families of suborder Mysticeti, also called the whalebone whales or great whales, as long ago as the middle Miocene. Little is known about when members of the various families in the Mysticeti, including the Balaenopteridae, diverged from each other.
Two subspecies have been identified—the northern sei whale (Balaenoptera borealis borealis) and southern sei whale (Balaenoptera borealis schlegelii). Their ranges do not overlap.
The Sei whale did not have meaningful international protection until 1970, when the International Whaling Commission (IWC) first set catch quotas for the North Pacific for individual species. Before quotas, there were no legal limits. Complete protection from commercial whaling in the North Pacific came in 1976.
Quotas on Sei whales in the North Atlantic began in 1977. Southern Hemisphere stocks were protected in 1979. Facing mounting evidence that several whale species were threatened with extinction, the IWC established a complete moratorium on commercial whaling beginning in 1986.
In the late 1970s, some “pirate” whaling took place in the eastern North Atlantic. There is no direct evidence of illegal whaling in the North Pacific, although the acknowledged misreporting of whaling data by the Soviet Union means that catch data are not entirely reliable.
The species remained listed on the IUCN Red List of Threatened Species in 2000, categorized as “endangered”. Northern Hemisphere populations are listed as CITES Appendix II, indicating they are not immediately threatened with extinction, but may become so if they are not listed. Populations in the Southern Hemisphere are listed as CITES Appendix I, indicating they are threatened with extinction if trade is not halted.
The Sei whale is listed on both Appendix I and Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix I as this species has been categorized as being in danger of extinction throughout all or a significant proportion of their range and CMS Parties strive towards strictly protecting these animals, conserving or restoring the places where they live, mitigating obstacles to migration and controlling other factors that might endanger them, and also on Appendix II, as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.
The Sei whale is covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU) and the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ACCOBAMS).
The species is listed as endangered by the U.S. government National Marine Fisheries Service under the U.S. Endangered Species Act.
(Source: Wikipedia – the Free Online Encyclopaedia)

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