Bryde's whale

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Bryde's Whales
Size comparison against an average human
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Eutheria
Order: Cetacea
Suborder: Mysticeti
Family: Balaenoptiidae
Genus: Balaenoptera
Species: brydei
edeni
omurai
Binomial name
Balaenoptera brydei
Olsen, 1913
Balaenoptera edeni
Anderson, 1879
Bryde's Whale range

Bryde's whales (pron.: /ˈbruːdə/ BREW-də) are baleen whales, the "great whales" or rorquals. They prefer tropical and temperate waters over the polar seas that other whales in their family frequent. They are largely coastal rather than pelagic. Bryde's whales are very similar in appearance to sei whales and almost as large.

The whales are named after Norwegian entrepreneur, Johan Bryde, who helped set up the first whaling station in Durban, South Africa in 1908.[2]

They inhabit tropical and subtropical waters worldwide. Bryde's whales are considered medium-sized for balaenopterids, dark gray in color with a white underbelly.

Contents

Etymology [edit]

In Japan, early whalers called it "iwashi" or "kutsuo kujira", the "anchovy" or "skipjack whale". It preys on the former, while it was commonly associated with the latter. As modern whaling shifted to Sanriku, whalemen confused it for the sei whale, and now the term "iwashi kujira" only applies to the latter species. Incidentally, anchovies are dominant prey for both species off Japan. They are now called "nitari kujira", or "look-alike whale", for their resemblance to the sei whale.[3]

Taxonomy [edit]

The taxonomy is poorly characterized. Three genetically distinct, candidate species/subspecies/morphologies, Bryde's whale B. brydei, Bryde's/Eden's whale B. edeni,[4] and Omura's whale B. omurai,[5] differentiate by geographic distribution, inshore/offshore preferences, and size. For at least two of the species, the scientific name B. edeni is common. Omura's whale, a pygmy, is only recently described and reaches only 11.5 m (38 ft).[6]

In 1878, the Scottish zoologist John Anderson, first curator of the Indian Museum in Calcutta, described Balaenoptera edeni, naming it after the former British High Commissioner in Burma, Sir Ashley Eden, who helped obtain the type specimen. Eden's Deputy Commissioner, Major A.G. Duff, sent a Mr. Duke, one of his assistants, to Thaybyoo Creek, between the Sittang and Beeling rivers, on the Gulf of Martaban, where he found a 37-ft whale, which had stranded there in June 1871 after swimming more than twenty miles up the creek — it was said to have "exhausted itself by its furious struggles" to get free and "roared like an elephant" before finally expiring. Despite terrible weather, he was able to secure almost the entire skull as well as nearly all its vertebrae, along with other bones. These were sent to Anderson, who described the specimen, which was physically mature, as a new species.[7] In 1913, the Norwegian scientist Ørjan Olsen, based on the examination of a dozen "sei whales" brought to the whaling stations at Durban and Saldanha, in South Africa, described Balaenoptera brydei, naming it after the Norwegian consul to South Africa Johan Bryde.[8] In 1950, the Dutch scientist G.C.A. Junge, after comparing specimens of B. edeni and B. brydei with a 39-ft physically mature specimen that had stranded on Pulu Sugi, an island between Singapore and Sumatra, in July 1936, synonymized the two species into B. edeni (Anderson, 1878).[9]

Description [edit]

Bryde's Whales are moderately-sized rorquals, falling behind sei whales but being larger than the relatively small minke whales. The largest measured by Olsen (1913) was a 14.95 m (49 ft) female caught off Durban in November 1912,[8] while the longest of each sex measured by Best (1977) at the Donkergat whaling station in Saldanha Bay, South Africa, were a 15.51 m (50.9 ft) female caught in October 1962 and a 14.56 m (47.8 ft) male caught in April 1963 – both were the offshore form.[10] At physical maturity, the coastal form off South Africa averages 13.1 m (43 ft) for males and 13.7 m (45 ft) for females, while the South Africa offshore form averages 13.7 m (45 ft) and 14.4 m (47.2 ft). The coastal form off Japan is slightly smaller, with adult males averaging 12.9 m (42.3 ft) and adult females 13.3 m (43.6 ft). At sexual maturity, males average 11.9 m (39 ft) and females 12 m (39.3 ft) off Japan. Sexual maturity is reached at 8–11 years for both sexes in the offshore form off South Africa. At birth, they are 3.95-4.15 m (13-13.5 ft).[11] The body mass of Bryde's whales can range from 12 to 25 metric tons (13 to 28 short tons).

Anatomy [edit]

See also: Whale anatomy
A Bryde's whale, showing faint lateral ridges

The Bryde's whale is a baleen whale, more specifically a rorqual belonging to the same group as blue whales and humpback whales. It has twin blowholes with a low splashguard to the front. Like other rorquals, it has no teeth, but has two rows of baleen plates.

Bryde's whales closely resemble their close relative the sei whale. They are remarkably elongated (even more so than fin whales), with the greatest height of the body being 1/7 their total length – compared to 1/6.5 to 1/6.75 in fin whales and only 1/5.5 in sei whales. Bryde's are dark smoky gray dorsally and usually white ventrally, whereas sei whales are often a galvanized blue-gray dorsally and have a variably sized white patch on the throat, a posteriorly oriented white anchor-shaped marking between the pectoral fins, and are blue-gray beyond the anus – although Bryde's off South Africa can have a similar irregular white patch on the throat. Bryde's have a straight rostrum with three longitudinal ridges that extend from the blowholes, where the auxiliary ridges begin as depressions, to the tip of the rostrum. The sei whale, like other rorquals, has a single median ridge, as well as a slightly arched rostrum, which is accentuated at the tip. Bryde's usually have dark gray lower jaws, whereas sei whales are lighter gray. Bryde's have 250-370 pairs of short, slate gray baleen plates with long, coarse, lighter gray or white bristles that are 40 centimetres (16 in) long by 20 centimetres (7.9 in) wide, while sei whales have longer, black or dark gray baleen plates with short, curling, wool-like bristles.[8]

The forty to seventy ventral pleats extend to or past the umbilicus, occupying about 58% and 57% of the total length, respectively – sei whales, on the other hand, have ventral pleats that extend only halfway between the pectoral fins and umbilicus, occupying only 45-47% of the total body length, whereas their umbilicus is usually 52% of the total body length. Both species are often covered with white or pink oval scars caused by bites from cookie-cutter sharks.[12]

Bryde's have an upright, falcate dorsal fin that is up to 46.25 cm (18.5 in) in height, averages 34.4 cm (13.75 in), and is usually between 30 and 37.5 cm (12 and 15 in).[10] It is often frayed or ragged along its rear margin and located about two-thirds the way along the back. The broad, centrally notched tail flukes never break the surface. The flippers are small and slender.[6]

Behavior [edit]

A Bryde's whale in False Bay, South Africa, showing upright dorsal fin, which is often nicked or frayed on its trailing edge (shown here)
A Bryde's whale off La Gomera, showing its culumnar blow

Their blow is columnar or bushy, about 10–13 feet (3.0–4.0 m) high. Sometimes they blow or exhale while under water. Bryde's whales display seemingly erratic behavior compared to other baleens, because they surface at irregular intervals and can change directions for unknown reasons.[6]

They usually appear individually or in pairs, and occasionally in loose aggregations of up to twenty animals around feeding areas.[6]

Breathing [edit]

They regularly dive for about 5–15 minutes (maximum of 20 minutes) after 4–7 blows. Bryde's whales are capable of reaching depths up to 1,000 feet (300 m). When submerging, these whales do not display their flukes. Bryde's whales commonly swim at 1–4 miles per hour (1.6–6.4 km/h), but can reach 12–15 miles per hour (19–24 km/h).[6]

They sometimes generate short (0.4 seconds) powerful, low frequency vocalizations that resemble a human moan.[6]

Diet [edit]

These whales opportunistically feed on plankton (e.g., krill and copepods), and crustaceans (e.g. pelagic red crabs, shrimp), as well as schooling fish (e.g., anchovy, herring, sardine, mackerel, and pilchard). Bryde's whales use several feeding methods, including skimming the surface, lunging, and bubble nets.[6]

Reproduction and nurturing [edit]

See also: Whale reproduction

Bryde's whales breed in alternate years, apparently in any season, with an autumnal peak. Their gestation period is estimated at 12 months. Calves are about 11–13 feet (3.4–4.0 m) long at birth and weigh 1,000 kilograms (2,200 lb). They become sexually mature at 8–13 years of age, when females are 39 feet (12 m). The mother nurses for 6–12 months.[6]

Range and habitat [edit]

Bryde's whales prefer highly productive tropical, subtropical and warm temperate waters of 61–72 °F (16–22 °C). Pygmies may prefer waters near the coast and continental shelf.[6]

Bryde's whales inhabit the Atlantic, Indian, and Pacific oceans, from 40° South to 40° North. Vagrants have been reported as far north as California and Washington. Some populations migrate seasonally, moving towards higher latitudes during the summer and towards the equator during the winter. Uniquely among baleen whales, some populations do not migrate.[6]

Population [edit]

There may be up to 90,000–100,000 animals worldwide, with two-thirds inhabiting the Northern Hemisphere.

For management purposes, the U.S. population is divided into three groups: the Eastern Tropical Pacific stock (11,000–13,000 animals), Hawaiian stock (350–500), and Northern Gulf of Mexico stock (25–40). Prior to 2006, there had only been two confirmed sightings of Bryde's whale in the eastern North Pacific north of Baja California—one in January 1963, only a kilometer off La Jolla (originally misidentified as a fin whale), and another in October 1991 west of Monterey Bay. Between August 2006 and September 2010, six sightings were made by scientists in the Southern California Bight. Five were west of San Clemente Island, and one between San Clemente Island and Santa Catalina Island. All but one involved single individuals.[13] Another sighting was made off Dana Point, California on September 19, 2009, which was originally misidentified as a fin whale.

There are insufficient data to determine population trends.

Conservation [edit]

An underwater view of a Bryde's whale off Thailand

Bryde's whale is listed as Data Deficient by the International Union for the Conservation of Nature and Natural Resources (IUCN). It is also listed in Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix I, which prohibits international trade.

The Bryde's whale is listed on Appendix II [14] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II [14] as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.

In addition, the Bryde's whale is covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU).[15]

Whaling [edit]

Historically, this species was not significantly targeted by commercial whalers, but became more important in the 1970s as the industry depleted other targets. The Japanese hunt this species as part of their scientific whaling program. Artisanal whalers have taken them off the coasts of Indonesia and the Philippines.

Modern whaling for Bryde's whales is thought to have begun from coastal stations in Japan in 1906, where it continued uninterrupted until 1987—they were also caught offshore in the western North Pacific by both Japanese (1971–79) and Soviet (1966–79) fleets, as well as from Taiwan (1976–80), the Bonin Islands (1946–52 and 1981–87) and the Philippines (1983–85). In 1997 it was estimated that over 20,000 Bryde's whales had been caught in the western North Pacific between 1911 and 1987 (it was later learned that the Japanese had falsified their reported take from the Bonin Islands between 1981–87, reporting a catch of only 2,659 instead of the true take of 4,162). A population assessment done in the mid-1990s stated that the population in the western North Pacific may have declined by as much as 49% during 1911–96. Norwegian factory ships off Baja California took an additional 34 Bryde's whales between 1924–29;[16] two were also caught off central California in 1966.[17]

An estimated 5,542 Bryde's whales were caught off Peru between 1968–83, including a reported catch of 3,589 between 1973–83. An unknown number were also caught off Chile between 1932–79. Over 2,000 were caught off Cape Province, South Africa, between 1911–67, most (1,300) during 1947–67. The majority of the 2,536 sei whales caught by the pirate whaler Sierra in the South Atlantic between 1969–76 are believed to have been Bryde's whales. At least some Bryde's whales were among the 5,000 sei whales recorded in the catch off Brazil between 1948–77, but possibly only 8%.[1]

Over 30,000 Bryde's whales were caught between 1911–87, including over 1,400 taken by the Soviets in the Southern Hemisphere between 1948–73 (only 19 were reported).[18] The peak reported catches were reached in 1973–74 and 1974–75, when over 1,800 were taken each year. In 2000 the Japanese began implementing a scientific research program involving an annual catch of 50 Bryde's whales in the western North Pacific. Nearly 500 have been caught since the program began (as of 2009).[19]

Other threats [edit]

Bryde's whales have not been reported as taken or injured in fishing operations. Bryde's whales are also sometimes killed or injured by ship strikes. Anthropogenic noise is an increasing concern for all rorquals, which communicate via low-frequency sounds.[6]

These whales are protected in the USA by the Marine Mammal Protection Act of 1972.[6]

See also [edit]

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References [edit]

  1. ^ a b Reilly, S.B., Bannister, J.L., Best, P.B., Brown, M., Brownell Jr., R.L., Butterworth, D.S., Clapham, P.J., Cooke, J., Donovan, G.P., Urbán, J. & Zerbini, A.N. (2008). "Balaenoptera_brydei". IUCN Red List of Threatened Species. Version 2011.1. International Union for Conservation of Nature. Retrieved 5 August 2011. 
  2. ^ Best, Peter B. 2007. Whales and Dolphins of the Southern African Subregion ISBN 978-0-521-89710-5
  3. ^ Omura, Hidero. "Review of the Occurrence of the Bryde's Whale in the Northwest Pacific". Rep. Int. Commn. (Special Issue 1), 1977, pp. 88-91.
  4. ^ Olsen, 1913
  5. ^ Wada, Oishi, and Yamada, 2003
  6. ^ a b c d e f g h i j k l "Bryde's Whale (Balaenoptera edeni)". Retrieved December 2009. 
  7. ^ Anderson, J. 1878. "Anatomical and Zoological Researches: Comprising an Account of the Zoological Results of the Two Expeditions to Western Yunnan in 1868 and 1875; and a Monograph of the Two Cetacean Genera, Platanista and Orcaella". Quaritch, London.
  8. ^ a b c Olsen, Ørjan. 1913. "On the External Characters and Biology of Bryde's Whale (Balaenoptera brydei), a new Rorqual from the Coast of South Africa". Proc. Zool. Soc. Lond., pp. 1073-1090.
  9. ^ Junge, G.C.A. 1950. "On a Specimen of the Rare Fin Whale, Balaenoptera edeni Anderson, stranded on Pulu Sugi near Singapore". Zool. Verhandl. 9, pp. 3-26.
  10. ^ a b Best, Peter B. "Two Allopatric Forms of Bryde’s Whale off South Africa". Rep. Int. Whal. Commn. (Special Issue 1), 1977, pp. 10-38.
  11. ^ Evans, Peter G. H. (1987). The Natural History of Whales and Dolphins. Facts on File.
  12. ^ Omura, H. 1966. "Bryde's whales in the Northwest Pacific". In Whales, Dolphins, and Porpoises (ed. K.S. Norris): 70-8. Univ. Calif. Press, Berkeley and Los Angeles.
  13. ^ Smultea, Mary A., Annie B. Douglas, Cathy E. Bacon, Thomas A. Jefferson, and Lori Mazzuca. "Bryde's Whale (Balaenoptera brydei/edeni) Sightings in the Southern California Bight". Aquatic Mammals (2012), 38 (1), pp. 92-97.
  14. ^ a b "Appendix II" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5th March 2009.
  15. ^ Official webpage of the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region
  16. ^ Tønnessen, Johan; Arne Odd Johnsen (1982). The History of Modern Whaling. University of California Press, Berkeley. ISBN 0-520-03973-4. 
  17. ^ Whaling in 1965–66 and summer 1966 (IWS). Luna.pos.to. Retrieved on 2011-09-15.
  18. ^ Berzin, A. 2008. The Truth About Soviet Whaling (Marine Fisheries Review), p 57.
  19. ^ International Whaling Statistics.

Bibliography [edit]

  • National Audubon Society Guide to Marine Mammals of the World, Reeves, Stewart, Clapham and Powell, 2002, ISBN 0-375-41141-0
  • Whales & Dolphins Guide to the Biology and Behaviour of Cetaceans, Maurizio Wurtz and Nadia Repetto. ISBN 1-84037-043-2
  • Encyclopedia of Marine Mammals, editors Perrin, Wursig and Thewissen, ISBN 0-12-551340-2
  • Whales, Dolphins and Porpoises, Carwardine (1995, reprinted 2000), ISBN 978-0-7513-2781-6

External links [edit]

Wikimedia Commons has media related to: Balaenoptera edeni
Wikispecies has information related to: Balaenoptera edeni
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