Blue Whale (Balaenoptera musculus)
Subspecies of the blue whale include:
- Northern Hemisphere blue whale (B. m. musculus)
- Antarctic blue whale (B. m. intermedia)
- Pygmy blue whale (B. m. brevicauda) - a significantly smaller and morphologically distinct form found in the subantarctic zone of the southern Indian Ocean and southwestern Pacific Ocean.
|Weight:||up to 330,000 pounds (150,000 kg)|
|Length:||up to 88-108 feet (27-33 m), depending on location (blue whales are largest in the Antarctic)|
|Appearance:||long body with mottled gray color pattern that appears light blue when seen through the water|
|Lifespan:||unknown, but sexually mature around 5-15 years|
|Behavior:||reproductive activity, including births and mating, mostly takes place during the winter|
The blue whale is species of baleen whale found worldwide. Blue whales in the Northern Hemisphere are generally smaller than those in the Southern Ocean. In the North Atlantic and North Pacific, they can grow up to about 88 feet (27 m), but, in the Antarctic, they can reach a up to about 108 feet (33 m) and can weigh more than 330,000 pounds (150,000 kg). As is true of other baleen whale species, female blue whales are somewhat larger than males.
Blue whales have a long-body and comparatively slender shape, a broad, flat "rostrum" when viewed from above, a proportionately smaller dorsal fin than other baleen whales, and a mottled gray color pattern that appears light blue (hence, the "blue" whale) when seen through the water.
The primary and preferred diet of blue whales is krill (euphausiids). In the North Atlantic, blue whales feed on two main euphausiid species (Thysanoëssa inermis and Meganyctiphanes norvegica). In addition, T. raschii and M. norvegica have been recorded as important food sources of blue whales in the Gulf of St. Lawrence. In the North Pacific, blue whales prey mainly on Euphausia pacifica and secondarily on T. spinifera. While other prey species, including fish and copepods, may be part of the blue whale diet, these are not likely to contribute significantly.
Scientists have yet to discern many details regarding the life history of the blue whale. The best available science suggests the gestation period is approximately 10-12 months and that blue whale calves are nursed for about 6-7 months. Most reproductive activity, including births and mating, takes place during the winter. Weaning probably occurs on, or en route to, summer feeding areas. The average calving interval is probably two to three years. The age of sexual maturity is thought to be 5-15 years. There are no known differences in the reproductive biology of blue whales in the North Pacific and North Atlantic oceans.
Blue whales are found worldwide, from sub-polar to sub-tropical latitudes. Poleward movements in spring allow the whales to take advantage of high zooplankton production in summer. Although the species is often found in coastal waters, blue whales are thought to occur generally more offshore than other whales, like humpback whales.
Blue Whale Range Map
(click for larger view PDF)
Blue whales are found in all oceans and are separated into populations by ocean basin in the North Atlantic, North Pacific, and Southern Hemisphere. They follow a seasonal migration pattern between summering and wintering areas, but some evidence suggests that individuals remain in certain areas year-round. The extent of knowledge concerning distribution and movement varies with area, and migratory routes are not well known. In general, distribution is driven largely by food requirements. For example, they occur in waters where krill is concentrated.
In the North Atlantic Ocean, blue whale range extends from the subtropics to the Greenland Sea. Blue whales are most frequently sighted in the waters off eastern Canada, with the majority of recent records from the Gulf of St. Lawrence, where they are present throughout most of the year. They are most common during the summer and fall feeding seasons and typically leave by early winter. Although they are rare in the shelf waters of the eastern U.S., occasional sightings of blue whales have been made off Cape Cod. It is believed this region may represent the current southern limit of the blue whales' feeding range. In addition, some evidence suggests that blue whales occur infrequently in the Gulf of Mexico and the Caribbean. Blue whales in the North Atlantic probably exist in two distinct populations.
In the North Pacific Ocean, the blue whale's range extends from Kamchatka to southern Japan in the west and from the Gulf of Alaska and California south to Costa Rica in the east. They occur primarily south of the Aleutian Islands and the Bering Sea.
Blue whales in the North Pacific probably exist in two sub-populations:
Kids' Times: Blue Whale [pdf]
Video: Blue whale story
Photo: NOAA's National Marine Sanctuaries
- Eastern North Pacific
- Western North Pacific
The Eastern stock is believed to spend winters off of Mexico and central America, and feed during summer off the U. S. West Coast and, to a lesser extent, in the Gulf of Alaska and central North Pacific waters.
The Western stock appears to feed in summer in the southwest of Kamchatka, south of the Aleutians, and in the Gulf of Alaska (Stafford, 2003 and Watkins et al., 2000). In winter, they migrate to lower latitudes in the western Pacific and, less frequently, in the central Pacific, including Hawaii (Stafford et al., 2001).
Blue whales accompanied by young calves have been observed often in the Gulf of California from December through March, and, thus, at least some calves may be born in or near the Gulf of California (Sears, 1990); this area is probably an important calving and nursing area for the species.
In the northern Indian Ocean, there is a "resident" population. Blue whale sightings have been reported from the Gulf of Aden, Persian Gulf, Arabian Sea, and across the Bay of Bengal to Burma and the Strait of Malacca. The migratory movements of these whales are unknown.
In the Southern Hemisphere, distributions of two subspecies (B. m. intermedia and B. m. brevicauda) seem to be segregated. B. m. intermedia occurs mainly in relatively high latitudes south of the "Antarctic Convergence" and close to the ice edge. B. m. brevicada is typically distributed north of the Antarctic Convergence.
|Southern Hemisphere||North Pacific||North Atlantic|
|Pre-whaling exploitation||150,000 - 200,000||4,900||1,100 - 1,500|
There are an estimated 5,000-12,000 blue whales remaining today, with the largest population of approximately 2,000 off the U.S. West Coast in the North Pacific.
The latest U.S. stock assessment reports of blue whales include data for various stocks, including areas of the Pacific and Atlantic Oceans.
While there is no current estimate for the number of blue whales in eastern North Atlantic waters, some data have been collected for blue whales in certain areas. In 1997, 32 individuals had been photo-identified in Icelandic waters. Additional studies have suggested that the population in Iceland and neighboring waters may be in the high hundreds (Gunnlaugsson and Sigurjónsson, 1990; Sigurjónssonand Gunnlaugsson, 1990) or even greater than 1,000 (Christensen et al., 1992). Sightings data off the west and southwest coasts of Iceland suggest the population has been increasing at about 5% per year since the late 1960s (Sigurjónsson and Gunnlaugsson, 1990).
- vessel strikes
- fisheries interactions
Additional threats that could potentially affect these populations include:
- anthropogenic noise
- habitat degradation, pollution
- vessel disturbance
- long-term changes in climate
Whaling substantially reduced blue whale populations worldwide during the early 1900s, but whaling is no longer considered a threat today.
Mortality and serious injury caused by ship strikes can be a threat to blue whales. The average number of blue whale mortalities in California attributed to ship strikes averaged 0.2 per year from 1998-2002. In September 2007, three blue whale deaths were confirmed to be caused by ship strikes in the Santa Barbara Channel off Southern California; these deaths were part of a larger Unusual Mortality Event.
In the western North Atlantic, at least 9% of whales in the Gulf of St. Lawrence have injuries or scars attributed to contact with ships (Sears et al., 1990). This area has a relatively high risk of ship strikes, because the St. Lawrence Seaway has heavy ship traffic during the time of year when blue whales are relatively abundant.
Though there is a lack of observed fisheries interactions in recent years, incidental take in fisheries threaten blue whales for two reasons. First, past records of entanglements suggest that interaction with fishing gear may affect blue whales. Second, entanglement rates may be underestimated because blue whales may break through or carry away fishing gear, perhaps suffering unrecorded subsequent mortalities or serious injuries. It is also likely that stranding data underestimate the number of whales killed by fishing gear, because most whales do not drift far enough to strand on beaches or to be detected floating nearshore. Direct observation of mortality is rare, but at least two documented cases of dead blue whales are apparently from the effects of entanglement in fishing gear (one in 1987 off Stellwagen Bank and the other in the 1990s in the Gulf of St. Lawrence).
Anthropogenic noise, habitat degradation, and vessel disturbance are additional concerns. However, there is little evidence available to describe or quantify the impacts of these threats on blue whales. For example, while anthropogenic noise may threaten other cetaceans, little is known about whether, or how, vessel noise affects blue whales.
Habitat degradation (for example, chemical pollution) has occurred in some areas of the North Atlantic (like the St. Lawrence River), but the impacts of this degradation are understudied have not been proven to affect blue whales (O'Shea and Brownell, 1994). Vessel disturbance (like whale-watching boats) may affect blue whales, but there is no direct evidence to demonstrate that persistent close approaches by tour boats has a negative effect on them.
From the early 1900s to the mid-1960s, blue whales were hunted in all the world's oceans, and their populations were significantly reduced. At least 9,500 blue whales were taken by commercial whalers throughout the North Pacific from 1910-1965 (Ohsumi and Wada, 1972) and at least 11,000 were taken in the North Atlantic from the 1890s-1960s (Sigurjónsson and Gunnlaugsson, 1990).
In 1966, the IWC banned commercial whaling for blue whales and no whaling (neither aboriginal subsistence nor commercial) occurs now. However, illegal whaling for blue whales has been documented or is likely to have occurred. A small number of illegal kills of blue whales have been documented in the Northern Atlantic off Canada and Spain, and in the eastern North Atlantic. Blue whales were also killed in the Southern Hemisphere by the Soviet Union after 1966 (Zemsky et al., 1995a, 1995b). Some illegal whaling by the USSR also occurred in the North Pacific (Yablokov, 1994), and it is likely that blue whales were among the species taken by these operations, but the extent is not known. Norwegian whaling operations target only minke whales, and the commercial whaling stations in Iceland, Spain, and the Portugese islands of the Azores and Madeira remain officially closed. Therefore, whaling activities, unless they are resumed, are not regarded as a threat to blue whale populations.
- Monitoring the status of the Eastern North Pacific Stock (CA-OR-WA) of blue whales via shipboard surveys
- Implementing a number of ship strike reduction measures in southern and central California
- Placing observers onboard vessels in the California/ Oregon swordfish/ thresher shark drift gillnet fishery to monitor the take of protected species, including other marine mammals
- Implementing marine mammal take reduction measures identified in the Pacific Offshore Cetacean Take Reduction Plan (including the use of acoustic pingers) to reduce the bycatch of blue whales and other marine mammals
In 1998, NMFS published a Blue Whale Recovery Plan [pdf]. The Plan details the comprehensive and long-term conservation efforts for blue whales. In April 2012, we announced that we intend to update the recovery plan for the blue whale and requested comments and information from the public.
The blue whale is listed as endangered throughout its range under the Endangered Species Act of 1973, and, thus, is listed as "depleted" throughout its range under the Marine Mammal Protection Act of 1972. Internationally, blue whales received complete legal protection from commercial whaling in 1966 under the International Convention for the Regulation of Whaling.
|Notice of Intent To Update a Recovery Plan for the Blue Whale and Prepare a Recovery Plan for the North Pacific Right Whale||77 FR 22760||04/17/2012|
|ESA Listing Rule||35 FR 18319||12/02/1970|
|Stock Assessment Reports||n/a||various|
- NMFS National Marine Mammal Laboratory Blue Whale Information and Research
- NMFS Southwest Fisheries Science Center (SWFSC) Blue Whale Information
- Stock Assessment Reports of blue whales in U.S. waters
- Kids' Times: Blue Whale [pdf]
- NOAA News: NOAA Scientists Sight Blue Whales in Alaska: Critically Endangered Blue Whales Rarely Seen in Alaska Waters (2004)
- NOAA's National Marine Sanctuaries
- Sounds of the Blue Whale from NOAA's Pacific Marine Environmental Laboratory
- U.S. Fish & Wildlife Service Blue Whale Species Profile
- Marine Mammal Commission
- International Whaling Commission
- IUCN Red List of Threatened Species
- Barlow, J. 1994. Abundance of large whales in California coastal waters: a comparison of ship surveys in 1979/80 and in 1991. Report to the International Whaling Commission. 44: 399-406.
- Bowles, A.E., M. Smultea, B. Würsig, D.P. DeMaster, and D. Palka. 1994. Relative abundance and behavior of marine mammals exposed to transmissions from the Heard Island Feasibility Test. J. Acoust. Soc. America 96:2469-2484.
- Calambokidis, J. 1995. Blue whales off California. Whalewatcher 29(1):3-7.
- Calambokidis, J., G.H. Steiger, J.C. Cubbage, K.C. Balcomb, C. Ewald, S. Kruse, R. Wells, and R. Sears. 1990. Sightings and movements of blue whales off central California 1986-88 from photo-identification of individuals. Report to the International Whaling Commission, Special Issue 12:343-348.
- Christensen, I., T. Haug, and N. Øien. 1992. Seasonal distribution, exploitation and present abundance of stocks of large baleen whales (Mysticeti) and sperm whales (Physeter macrocephalus) in Norwegian and adjacent waters. ICES J. mar. Sci. 49:341-355.
- Clapham, P.J., and R.L. Brownell, Jr. 1996. Potential for interspecific competition in baleen whales. Report to the International Whaling Commission. 46:361-367.
- Gunnlaugsson, T., and J. Sigurjónsson. 1990. NASS-87: Estimation of whale abundance based on observations made on board Icelandic and Faroese survey vessels. Report to the International Whaling Commission. 40:571-580.
- IUCN Red Data Book. 1991. Dolphins, Porpoises, and Whales of the World. IUCN. Gland, Switzerland.
- Jefferson, T.A., M.A. Webber, and R.L. Pitman. 2008. Marine Mammals of the World. Academic Press.
- Ohsumi, S., and S. Wada. 1972. Stock assessment of blue whales in the North Pacific. Unpublished working paper for the 24th meeting of the Scientific Committee of the International Whaling Commission, 20 pp.
- O'Shea, T.J., and R.L. Brownell, Jr. 1994. Organochlorine and metal contaminants in baleen whales: a review and evaluation of conservation implications. Sci. Total Environment 154:179-200.
- Perry, S. ., D.P. DeMaster, and G.K. Silber. 1999. The Great Whales: History and status of six species listed as Endangered under the U.S. Endangered Species Act of 1973. Marine Fisheries Review 61 (I): 1-74.
- Rice, D.W. 1986. Blue whale. Pp. 4-45 In: D. Haley (ed.) Marine mammals of eastern North Pacific and Arctic waters. Second edition. Pacific Search Press.
- Sears, R. 1990. The Cortez blues. Whalewatcher 24(2):12-15.
- Sears, R., F.W. Wenzel, and J.M. Williamson. 1987. The Blue Whale: A Catalogue of Individuals from the Western North Atlantic (Gulf of St. Lawrence). Mingan Island Cetacean Study, St. Lambert, Quebec. 27 pp.
- Sears, R., J.M. Williamson, F.W. Wenzel, M. Bérubé, D. Gendron, and P. Jones. 1990. Photographic identification of the blue whale (Balaenoptera musculus) in the Gulf of St. Lawrence, Canada. Report to the International Whaling Commission, Special Issue 12:335-342.
- Sears, R. and W.F. Perrin. 2009. Blue Whale. In: Encyclopedia of Marine Mammals. W.F. Perrin, B. Wursig, and J.G.M. Thewissen (eds.). Academic Press.
- Sergeant, D.E. 1966. Populations of large whale species in the western North Atlantic with special reference to the fin whale. Fisheries Research Board of Canada, Arctic Biological Station, Circular No. 9.
- Sigurjónsson, J., and T. Gunnlaugsson. 1990. Recent trends in abundance of blue (Balaenoptera musculus) and humpback whales (Megaptera novaeangliae) off west and southwest Iceland, with a note on occurrence of other cetacean species. Report to the International Whaling Commission. 40:537-551.
- Stafford, K.M. 2003. Two types of blue whale calls recorded in the Gulf of Alaska. Marine Mammal Science. 19: 682-693.
- Stafford, K.M., S.L. Nieukirk, and G.G. Fox. 2001. Geographic and seasonal variation of blue whale calls in the North Pacific. Journal of Cetacean Research and Management 3(1): 65-76.
- Watkins, W.A., J.E. George, M.A. Daher, K. Mullin, D.L. Martin, S.H. Haga, and N.A. DiMarzio. 2000. Whale call data for the North Pacific November 1995 through July 1999: Occurrence of calling whales and source locations from SOSUS and other acoustic systems. Technical Report WHOI_00_02 available from Woods Hole Oceanographic Institution. 160pp.
- Yablokov, A.V. 1994. Validity of whaling data. Nature 367:108.
- Yochem, P.K., and S. Leatherwood. 1985. Blue whale Balaenoptera musculus (Linnaeus, 1758). Pp. 193-240 In: Ridgway, S.H. and R. Harrison (eds.), Handbook of Marine Mammals, Vol. 3: The Sirenians and Baleen Whales. Academic Press, London. 362 pp.
- Zemsky, V.A., A.A. Berzin, Y.A. Mikhaliev, and D.D. Tormosov. 1995a. Soviet Antarctic pelagic whaling after WWII: review of actual catch data. Report of the Sub-committee on Southern hemisphere baleen whales. Rep. int. Whal. Commn. 45:131-135.
- Zemsky, V.A., A.A. Berzin, Y.A. Mikhaliev, and D.D. Tormosov. 1995b. Antarctic whaling data (1947-1972). Center for Russian Environmental Policy, Moscow. 320 pp. [In Russian with English summaries.]
Updated: February 27, 2013