Taxonomy

This species was first described in 1878 based on a specimen stranded in Burma. The common name, Bryde's whale, was given in honor of Norwegian consul Johan Bryde, who built the first whaling stations in South Africa. In 1913, the species was described by Olson as Balaenoptera brydei. In 1950, Junge concluded that the descriptions of B. edeni and B. brydei were synonymous and that therefor B. edeni, being the first, should be the species name. There appear to be a number of different morphological forms of the Bryde's whale, which may be either regional differences or may be different subspecies. Rice (1998) states that there is a growing body of evidence that B. edeni and B. brydei should be considered separate species.

Appearance

Bryde's whales typically reach a length of 13 m, with a maximum of 15.3 m. Females are slightly larger than males. The color is variable, but usually the dorsal side is blueish black and the ventral side white or yellowish. A dark blueish grey area extends from the throat to the flippers.

The flippers are slender and somewhat pointed. The dorsal fin is pointed and falcate. The ventral grooves extend to the umbilicus. In the sei whale, the grooves end mid-body. A feature, unique to the Bryde's whale is the presence of 2 lateral ridges that run from the tip of the snout to the blowholes, one on each side of the median ridge that is common to all rorqual whales.

The baleen is about 19 cm wide and about 50 cm long. The inner margin is concave. They usually have 250-280 fully developed baleen plates

Distribution

Probably, the Bryde's whale does not migrate a lot. There are indications of some shifts towards the equator in winter and towards the temperate zones in summer. The Bryde's whale can be found in the tropical and temperate areas of the Southern Pacific, Atlantic and Indian Oceans. On the Northern hemisphere, this species can be found in the tropical and temperate areas of the Pacific and the Western Atlantic, as well as in the Indian Ocean.

Population dynamics and life history

Females become sexually mature at about 12 m in length, at which time they are probably 10 years of age (age determination based on laminations in the ear plug). Males become sexually mature at the age of 9-13 years (12 m in length). Gestation lasts about 1 year. Neonate calves are about 3.4 m in length. The calves are approximately 7.1 m when they are weaned at about 6 months. Female probably give birth less than once every two years.

Population status

Until the 1970s, catches of Bryde's whales were recorded with those of sei whales. Because of this the status of this species is rather unclear. The International Whaling Commission recognizes the following stocks:

• Indian Ocean. The Northern Indian Ocean stock was initially classified as an IMS (Initial Management Stock) with a zero catch limit, pending proper population estimates. In 1980, it was decided to treat the whole Indian Ocean as a single stock area. The total population in that area was estimated at 13,854 animals.
• Northern Atlantic. Classified as IMS and no population estimate is available.
• Western North Pacific. The exploitable population was estimated at 32,000 individuals in 1946 and 23,500 in 1987. Other calculations suggested a 1946 population of 26,000 and a 1987 population of 17,000. In 1988, the population was estimated to be 18,000 individuals.
• Eastern North Pacific. Not much information is available on this population. The area between 10N and 7S and between 90W and 110W has an estimated size of 10,000 individuals.
• East China Sea. This stock was recognized in 1979. Its status is unknown, although it has probably been exploited at a low level for some time.
• Southern Atlantic. This area contains 3 stocks: a Brazilian, a South African coastal stock and a pelagic stock. Little is known about these stocks.
• Peru. In 1983, this stock was estimated at 15,638 individuals (range: 5,723 - 25,550). The 1968 population was estimated at 19,426 individuals (range: 9,692 - 29,519).
• Solomon Islands. There is one highly unreliable estimate for 1980 of 1,800 individuals available for this stock. No further estimates have become available.
• Western South Pacific. In 1980, the population was estimated to consist of 16,585 individuals. However, there are some doubts about the validity of this estimate. No new estimates have become available.
• Eastern South Pacific. In 1980, this population had an estimated size of 13,194 individuals. However, it was noted that catches seemed to have a considerable impact on this population, which cast doubt on the original estimates. The population was then classified by the IWC as an IMS with a zero catch limit.

The IUCN lists this species as Insufficiently known.

Exploitation

The exploitation history of the Bryde's whale is somewhat obscure. Prior to 1970, the catches of Bryde's whales were included in the catch statistics for the sei whale. Once the Bryde's whale was treated at a separate species by the IWC, there have been commercial catch quota set for only a limited number of stocks, due to the uncertainties of the sizes of the various populations. A number of animals have been collected under scientific permits. The following catch quota were set:

• Indian Ocean: 197 in 1980. A zero catch limit was adopted as of 1982.
• East China Sea: no whales were reported taken between 1975 and 1980. One was taken in 1981. In 1980 the catch limit was set to 19, in 1983 to 10. After that a zero limit was implemented.
• Southern Atlantic: from 1947 to 1980 an estimated 350 whales were taken from this stock (listed originally as sei whale catches). Since 1982 there was a zero limit for this stock.
• Peru: in 1984 a catch limit of 165 was set for this stock. No change was implemented until the 1986 moratorium on commercial whaling.
• Eastern South Pacific: in 1980, a catch limit of 188 was set for this population. Due to doubts about population estimates, this was reduced to a zero catch limit in 1982. From 1946 to 1979 an estimated 1,380 whales were taken from this population.

Feeding

In some areas, the Bryde's whale feeds predominantly on krill. In other areas, schooling fish, such as pilchards, anchovies, herring and mackerel, seem to be preferred. Also bonito, shark and squid have been reported as being part of the diet of this species.

References

Cummings, W.C. (1985)

Bryde's whale Balaenoptera edeni Anderson, 1878. In: S.H. Ridgway and R.J. Harrison (eds.): Handbook of Marine Mammals, Vol. 3: The Sirenians and Baleen Whales. pp.137-154. Academic Press.

Klinowska, M. (1991)

Dolphins, Porpoises and Whales of the World. The IUCN Red Data Book. IUCN, Gland, Switzerland.

Rice, D.W. (1998)

Marine mammals of the world - Systematics and distribution
Society of Marine Mammalogy Special Publication Number 4, 231 pp.

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