The Blue Whale is a blue-steel gray member of the family Balaenopteridae (Rorquals), the same family as the Fin Whale and the Sei Whale. It is primarily an open ocean species and is the largest species on Earth. The longest Blue Whale measured by scientists was 29.9 metres (98 ft), although lengths up to 33 metres have been reported (Wikipedia 2011).
Gregr et al. (2006, 3) provide the following description: "Blue whales have a light to slate-grey appearance above water with a characteristic mottled pigmentation. The pigmentation can range from a sparse mottling pattern to
highly mottled individuals with splotches along the flanks, back and ventral surface.
3 Chevrons often curve down and back on both sides of the rostrum behind the blowholes...The blue whale has a large, broad U-shaped head that comprises nearly 25% of its body length. The top of the head has a prominent rostral ridge that runs from the upper
jaw and mandibles to the splash-guard in front of two blowholes. The dorsal fin is
relatively small compared to other balaenopterids and is highly variable in shape. The
flippers are approximately 4 m in length (15% of body length) with blunt tips. The flukes are broad and triangular with a straight or slightly curved trailing edge, grey in colour, possibly with variable white patches on the underside." 60-88 pleats extend from the throat approximately to the navel and the mouth has 260 to 400 beleen plates (Jefferson et al. 2008).
Identification and Subspecies Information
Four subspecies are presently recognized: Balaenoptera musculus musculus (North Atlantic, North Pacific), Balaenoptera musculus. indica (northern Indian Ocean), Balaenoptera musculus intermedia(Southern Hemisphere) and Balaenoptera musculusbrevicauda (Southern Hemisphere and northern Indian Ocean), however, Balaenoptera musculus indica may or may not be a valid subspecies (Jefferson et al. 2008). Hybrids between Blue and Fin Whales are reported (Jefferson et al. 2008, and others).
Biology
Behaviour
Blue Whales migrate each year to feeding grounds and may be solitary or occur in small groups--although as many as 60 have been seen at one time. They can swim at speeds up to 30 mph.
Biology
Diet:
Blue Whales feed on zooplankton, filtering food through their baleen. "They feed primarily on euphausiids (Euphausia pacifica, Thysanoessa spinifera, T. inermis, T. longpipes, T. raschii, and Nematoscelis megalops), though calanoid copepods (Calanus spp.) and pelagic red crab (Pleuroncodes planipes) also occur in the diet." (Gregr et al. 2006, 6).
Reproduction:
Calves are born in winter in tropical/subtropical regions (Jefferson et al. 2008). Gregr et al. (2006) provide some insights into reproduction in Blue Whales: Females breed every 2-3 years, but calving rates are not well known, calves are 6-7 m in length at birth, they are weaned at 6-7 months while still in the feeding grounds.
Distribution
Global Range
The Blue Whale is found in most oceans in the world. They are found "from the pack ice of both hemispheres to temperate and tropical waters, with distinct populations found in the North Atlantic, North Pacific, Southern Hemisphere, and the northern Indian Ocean",(Gregr et al. 2006). Although wide-ranging, they are not typically found in equatorial waters (Jefferson et al. 2008).
In Canada, this species is found in the North Pacific and the North Atlantic (Gregr et al. 2006). "Historically, blue whales ranged throughout the coastal and pelagic waters of the North Pacific... Based on whaling records, Gambell (1979) suggested that there were three blue whale populations in the North Pacific, while Reeves et al. (1998) concluded that as many as five sub-populations, including ones in the eastern Gulf of Alaska and California/Mexico, inhabited the North Pacific with an uncertain level of mixing between them. The lack of recent sighting data in much of the species’ former range suggests that some sub-populations may have been extirpated by commercial whaling." (Gregr et al. 2006, 4). The breeding grounds are not well-defined (Jefferson et al. 2008).
Distribution in British Columbia
Gregr et al. (2006) indicate that the eastern North Pacific population represents a large proportion of the known Blue Whales in the world, and while sightings of Blue Whales in BC are rare, calls are consistently heard from California to BC. Pacific Canadian waters "may represent an important feeding ground for a large portion of the world's Blue Whales" (Gregr et al. 2006, 6). Some detail on the presence of Blue Whales in BC waters are provided by Gregr et al. 2006 (pages 4-6), and this includes calls heard off Vancouver Island, sightings by Japanese surveys in Canadian waters, a tagged whale off Vancouver Island, two Blue Whales photo-identified off the Queen Charlotte Islands, and two Blue Whales sighted near the shelf-break off Queen Charlotte Sound in the spring of 2002.
Conservation
Conservation Issues
The Pacific population of the Blue Whale was listed as an endangered in Canada in 2002. Reason for designation is given as: "Blue whales off the coast of British Columbia are likely part of a population based in the northeastern Pacific. The population was reduced by whaling. The rarity of sightings (visual and acoustic) suggests their numbers are very low (significantly less than 250 mature individuals). Threats for blue whales along the coast of British Columbia are unknown but may include ship strikes, pollution, entanglement in fishing gear, and long-term changes in climate (which could affect the abundance of their zooplankton prey)." (Gregr et al. 2006).
Populations of Blue Whales were decimated globally by whaling in the early 1900's.
Gregr, E.J., J. Calambokidis, L. Convey, J.K.B. Ford, R.I. Perry, L. Spaven, and M. Zacharias. 2006. Recovery Strategy for Blue, Fin, and Sei Whales (Balaenoptera musculus, B. physalus, and B. borealis) in Pacific Canadian Waters. IN Species at Risk Act Recovery Strategy Series. Vancouver: Fisheries and Oceans Canada. vii + 53 pp. Available online.
Jefferson, Thomas A., Marc A. Webber and Robert L. Pitman. 2008. Marine Mammals of the World: A Comprehensive Guide to their Identification. Elsevier, New York. Available online.
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2021. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
2024-10-13 9:31:18 AM]
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