||It has been suggested that Balaenoptera brydei be merged into this article. (Discuss) Proposed since August 2013.|
|Size compared to an average human|
|Bryde's Whale range|
The Bryde's whale complex (// BREW-də) comprises two putative species of rorqual: Bryde's whale (Balaenoptera brydei, Olsen, 1913), a larger form that occurs worldwide in warm temperate and tropical waters, and the sittang or Eden's whale (B. edeni, Anderson, 1878), a smaller form that may be restricted to the Indo-Pacific. There is also a smaller, coastal form of B. brydei off southern Africa, and perhaps another form in the Indo-Pacific which differs in skull morphology, tentatively referred to as the Indo-Pacific Bryde's whale. The recently described Omura's whale (B. omurai, Wada et al. 2003), was formerly considered a "pygmy" form of Bryde's, but is now recognized as a distinct species.
B. brydei gets its specific and common name from Johan Bryde, Norwegian consul to South Africa who helped establish the first modern whaling station in the country, while B. edeni gets its specific and common name from Sir Ashley Eden, former High Commissioner of Burma (Myanmar). Sittang whale refers to the type locality of the species.
In Japan, early whalers called it "iwashi" or "katsuo 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.
The taxonomy is poorly characterized. There are two genetically distinct, candidate species/subspecies/morphologies, Bryde's whale B. brydei, and the Sittang or Eden's whale B. edeni, which differentiate by geographic distribution, inshore/offshore preferences, and size. For both putative specices the scientific name B. edeni is commonly used or they are simply referred to B. cf brydei/edeni.
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. 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. 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).
Members of the Bryde's whale complex are moderately-sized rorquals, falling behind sei whales but being larger than Omura's whale and 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, 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. 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). The body mass of Bryde's whales can range from 12 to 25 metric tons (13 to 28 short tons).
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.
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.
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). 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.
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.
They usually appear individually or in pairs, and occasionally in loose aggregations of up to twenty animals around feeding areas. They are more active on water surface than Sei whales, and this tendency becomes even stronger in coastal form.
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).
They sometimes generate short (0.4 seconds) powerful, low frequency vocalizations that resemble a human moan.
Bryde's whale feed on a wide variety of fish, planktonic crustaceans, and cephalopods. In the western North Pacific, Bryde's whale caught by Japanese scientific whaling vessels (2000-2007) mainly fed on Japanese anchovy (Engraulis japonicus, 52%) and various species of euphausiid (36%, including Euphausia similis, E. gibboides, Thysanoessa gregaria and Nematoscelis difficilis), as well as oceanic lightfish (Vinciguerria nimbaria, nearly 3%), and mackerels (Scomber spp., less than 2%). The prey differed by location and season. In coastal areas, euphausiids dominated the diet, comprising 89 and 75 percent of the diet in May and June, respectively. Further offshore, Japanese anchovy was the dominant species, accounting for nearly 100 percent of the diet in late summer. Based on the stomach contents of Bryde's whales caught by Japanese pelagic whaling expeditions in the North Pacific in the 1970s, the majority where found to feed on euphausiids (nearly 89%), whereas only about 11 percent fed on fish.
Off South Africa, prey preferences differed between the inshore and offshore forms. The former mainly feed on anchovies (Engraulis capensis, 83%), maasbankers (Trachurus trachurus, 36%), and pilchards (Sardinops ocellata, 33%), with only one (or 3%) being found with euphausiids (Nyctiphanes capensis). The latter, on the other hand, mainly feed on euphausiids (primarily Euphausia lucens, but also E. recurva, N. capensis, and Thysanoessa gregaria), as well as various deep-sea fish (including Mueller's pearlside, Maurolicus muelleri, and a species of Lestidium). One was even found "full of baby squid" (later identified as Lycoteuthis diadema).
In the Gulf of California, they mainly feed on Pacific sardine (Sardinops sagax) and thread herring (Opisthonema libertate) (about 88%), but also feed on euphausiids (mostly Nyctiphanes simplex, 11%). They've also been observed feeding on pelagic red crabs (Pleuroncodes planipes) off southern Baja California. In the Coral Sea, the South Pacific, and the Indian Ocean they appear to mainly feed on euphausiids, while off Brazil they have been observed feeding on sardines. Individuals caught off Western Australia were found with anchovies (E. australis) in their stomachs (though these individuals may refer to Omura's whale).
Bryde's whales use several feeding methods, including skimming the surface, lunging, and bubble nets.
Reproduction and nurturing
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.
B. brydei occurs in the Atlantic, Pacific, and Indian oceans between the 40th parallels of latitude, preferring highly productive tropical, subtropical and warm temperate waters of 61–72 °F (16–22 °C). In the North Pacific, they occur as far north as Honshu to the west and southern California in the east, with vagrants reported as far north as Washington State in the United States. There is a resident population in the Gulf of California and they occur throughout the eastern tropical Pacific, including Peru and Ecuador, where they are absent from July to September. They have also been reported in an upwelling area off Chile between 35° and 37°S. In the southwestern Pacific, they occur as far south as the North Island of New Zealand. Based on osteological features a specimen from Taiwan was referred to B. brydei, while several specimens from the Philippines and Indonesia differed slightly in skull morphology and were referred to the putative Indo-Pacific Bryde's whale. Mitochondrial DNA analysis showed that Bryde's whales caught in the pelagic western North Pacific and Bonin Islands (resident population exists), as well as biopsy samples taken from whales off Hawaii, the west coast of Baja California, and the southern Gulf of California, belonged to B. brydei.
B. brydei occurs throughout the Indian Ocean north of about 35°S. Those of the southern Indian Ocean appear to correspond to B. brydei, as do the individuals illegally caught by the Soviets in the 1960s in the northwest Indian Ocean as well as the Maldives. Individuals sighted in the Red Sea may or may not be referable to B. brydei.
In the North Atlantic, they have been recorded as far north as Cape Hatteras. They occur in the Gulf of Mexico and throughout the wider Caribbean – two specimens from Aruba were found through mtDNA analysis to be firmly placed within B. brydei and to form a clade with a specimen from Madeira and individuals of the offshore form of South Africa. They were first recorded in the Azores in 2004, but do not occur in the Mediterranean. They appear to occur off Brazil year-round. Individuals of the inshore form off South Africa are also resident year-round, occurring mainly between Cape Recife and Saldanha Bay, whereas the larger offshore form migrates to West African equatorial waters in the winter.
The type specimen is from the Gulf of Martaban coast of Myanmar, while other referred specimens were found on the Bay of Bengal coast of Myanmar, Bangladesh, India, Thailand, and Taiwan. A population found off southern and southwestern Japan in the East China Sea has also been referred to B. edeni. A whale that stranded in Hong Kong and another saved from a river in eastern Australia were found to be closely related to the Junge specimen and the East China Sea whales. Bryde's whale (most had auxiliary ridges) of small size – estimated at 10.1 to 11.6 m (33 to 38 ft) in length – sighted off the northeastern side of the Solomon Islands during a survey in late November and early December 1993 may be referable to B. edeni. Four of the whales – estimated at 11.3 to 11.6 m (37 to 38 ft) in length – were accompanied by calves – which ranged from 6 to 6.7 m (19.5 to 22 ft) in length. It is unknown whether eight small individuals – reaching only 11.2 to 11.7 m (36.7-38.4 ft) at maturity – caught off western and eastern Australia between 1958 and 1963 are specimens of B. edeni or B. omurai.
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).
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. Another sighting was made off Dana Point, California on September 19, 2009, which was originally misidentified as a fin whale.
In general, there are insufficient data to determine population trends.
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  of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II  as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.
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; two were also caught off central California in 1966.
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%.
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). 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).
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.
These whales are protected in the USA by the Marine Mammal Protection Act of 1972.
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