Blue Whales

      The largest mammal in the world and the largest animal ever known to have live on earth is believed to be the Blue Whale (Balaenoptera musculus). [1] An average individual weighs 100 tons (90 metric tons) and is 70 feet  (21m) long. At the American Marine Mammal Laboratory (NMML), the longest whale measured by scientists was 29.9 m long (98 ft) – about the same length as a Boeing 737 airplane, and is believed  to be in excess of 180 tons (200 metric tons). The female blue whales are somewhat larger than the males.[2] It gives birth to a calf that averages 25 ft in length and weighs about 2 tons.[3] Everyday, the calf drinks about 106 gallons of milk during the first seven months of its life. An average adult pumps 2500 gallons of blood and burns 3 million calories a day.

      The Blue Whales’ upperparts of the body are mottled blue-gray and its undersides are whitish or light yellow. The dorsal finis relatively small, visible only briefly when diving.3  Speeds of 50 km/hr (30mph) over short burst were recorded among the whales when interacting with other whales, but 20 km/hr (12mph) is its more typical travelling speed. They slow down to 5 km/hr (3mph) when feeding.

      In most oceans around the world, Blue Whales were said to be abundant until the beginning of the 20^th century. Whalers hunted them almost to extinction for the first 40 years of that century.  It is only in 1966 that the International community outlawed the hunting of the species.1 A report on 2002 estimated that Blue whales worldwide were 5,000 to 12,000.[4] The largest population of Blue Whales was in the Antarctic before they were overexploited due to whaling.[5] 

HISTORY

      In the 19^th century, the sailing-vessel whalers only occasionally hunted Blue Whales. In the second half of that century, the introduction of steam power made it possible for boats to overtake the large, fast-swimming blue whales and rorquals. By the early 1870’s, most of the technology for “modern” whaling was available and factory ships were added in the early 20th century.[6] This includes the invention of the exploding harpoon gun which revolutionized the whaling industry. The said industry began to focus on blue whales after 1900.

      Blue Whales in the Southern Hemisphere portion were protected beginning in1939. In 1955, under the International Convention for regulation of Whaling, they were given complete protection in the North Atlantic and this was extended to the Antarctic in 1965 and the North Pacific in 1966.[7]

      Blue Whales are protected under both the Endangered  Species Act (ESA) (as an endangered species) and the Marine Mammal Protection Act (MMPA).[8]

DISTRIBUTION

            In all oceans of the world, Blue Whales maybe found. They migrate to tropical-to-temperate waters during winter months to mate and give birth to calves.[9]

Blue whales have been seen north of Svalbard, 1500km from the North Pole, and along the Ross Ice Shelf edge,  the most southerly marine waters of the planet. However, they are not evenly distributed, there seems to be several distinct populations, possibly comprising up to 4 separate sub-species in the north Pacific and north Atlantic, the northern Indian Ocean, the Antarctic and the sub-Antarctic regions of the Indian Ocean.[10]

            It is assumed that Blue Whale distribution is governed largely by its food requirements and that populations are seasonally migratory. Poleward movements in spring allow the whales to take advantage of high zooplankton production in summer. In the fall, blue whales move towards the subtropics to reduce their energy expenditure while fasting, avoid ice entrapment in some areas, and engage in reproductive activities in warmer waters of lower latitudes.[11]

POPULATION

      It is not well known whether the blue whale population worldwide is increasing or remaining stable since whaling was banned or outlawed. In the beginning of the 20^th century, it is estimated that there were between 275,000 to 300,000 blue whales in the world, of which around 250,00 of the vast majority were in the Antarctic.10 Today the number is probably around 5,000. In the north Atlantic, there are perhaps 1,000 or 2,000; in the north Pacific, the range is somewhere 1,400 to 4,000. In the Antarctic, there are probably fewer than 1,000 – possibly just 400.10

      In some reports, the total global population of blue whales was estimated to range between 5,000 to 12,000 in 2002 although there is great uncertainty in available estimates for many areas.4 The Blue whale remains listed as “endangered” on the  International Union for Conservation of Nature and Natural Resources (IUCN) Red List of threatened species as it has been since the list’s inception.

CAUSES OF ITS LOW POPULATION

Whaling

1. Commercial Whaling

            Commercial whaling likely began in the North sea in the 9^th century and in the Gulf of Gascogne in the 12^th century.[12] When the populations of right whale started to diminish over the course of the 16^th century in Europe, whalers headed for North America.  A veritable industry then developed along the coast of North America over the centuries. Thousands of whales are hunted every year. The hunt intensified with the advent of more powerful ships and invention of the exploding harpoon. Over 2 million whales were taken in the Antarctic Ocean alone in the year 1904 to 1985. This hunt depleted  several species to the point of near extinction.

1. Scientific whaling

            Precious information concerning cetaceans was furnished by intensive whaling. However, several species was brought to near extinction by it. Certain countries like Japan and as of 2003, Iceland  continue to hunt whales under the guise of  science.12 It is stated in the International Whaling Convention (IWC) signed in 1946, that each member country be allowed the option of granting itself scientific whaling permits.

       Japan carried out two whaling programs.12 The oldest takes place in Antarctica, where Japan kills over 400 minke whales on an annual basis. The program is aimed at estimating certain biological parameters – such as the natural death rate – and the study of the role of minke whales in the Antarctic ecosystem. The second program began in 1994 which involves killing of 100 minke whales in the North Pacific. The program is aimed on the feeding ecology of minke whales for better understanding. As stipulated in the IWC, whale products are then sold on local markets. Critics of this hunt state that this scientific whaling is nothing more than a pretext to maintain a demand for whale products and encourage a resumption of commercial whaling.

1. Subsistence Whaling

            Subsistence whaling according to the International Whaling Commission (IWC) is hunting that is carried out by native peoples that share strong community, family, social and cultural bonds that connect them to a traditional dependence on whaling and whale products. Also, the purpose of the hunt must be for the native people consumption only and be aimed at meeting their cultural and nutritional requirements.12

Entrapment and Entanglement in Fishing Gear

            Entanglement is a major problem for which there is still no solution. The lack of  more evidence that blue whales become entrapped or entangled in fishing gear may be due to incomplete reporting. In addition, the large size of these creatures makes it more likely that they will break through nets or carry away with them  the gear. In the latter case, undetected mortality may be attributed from starvation due to interference in feeding as sometimes occurs in humpback and north right whales.12

Disturbance by Vessels

            The presence of vessels could greatly reduce the feeding efficiency of fin whales.12 In the presence of a large number of boats, fin whales dive for shorter periods of time. This behavior change could therefore reduce the time dedicated to capturing prey. Consequently, even if the feeding efficiency is reduced only slightly, the cumulative effects should have serious repercussions on the ability of this animal to store up the energy reserves that they need.

Collision with ships

             Collisions with ships are relatively common. While Cetaceans can rapidly react to danger, in certain situations, such as when they are resting at the surface, eating, nursing or mating, they are said to be less alert, thereby resulting in ship strikes.12

WHAT COULD BE DONE TO HELP THEM

            Creation and promotion of programs and research projects that is aimed in learning to better understand the biology of the blue whale, the threats that weigh upon  their population and the actions that favor its recovery should be given importance. Conservation strategies of this species also need to be formulated to increase their chances of survival.

References:

¹     Blue Whale – Wikepedia, the free encyclopedia (2006)

    Retrieved on October 1, 2006 at http://en.wikipedia.org/wiki/Blue_Whale

²   Ralls, K. (1976) Mammals in which females are larger than males. Q. Rev. Biol.

   51:245-270.

³    Blue Whale Fact Sheet, retrieved  on October 1, 2006 at

   http://  www.dec.state.ny.us/website/dfwmr/wildlife/endspec/blwhfs.html

⁴   Committee on the Status of Endangered Wildlife in Canada (2002)

   Assessment and update Status report on the Blue Whale Balaenoptera musculus

   Populayion size and Trends, retrieved on October 1, 2006 at

   http://www.wildwhales.org/cetaceans/blue/sr_blue_whale_e.pdf.pdf

⁵  Branch, T.A., Matsuoka, K. and Miyashita, T., (2004) “Evidence for increases in  Antarctic blue whales based on Bayesian modelling”. Marine Mammal Science 20: 726-754.

⁶  Tønnessen,J.N., and Johnsen, A.O., (1982) The History of Modern Whaling. Univ.       of California Press, Berkeley. 798 pp. 

⁷  Best, P.B. (1993) Increase rates in severely depleted stocks of baleen whales.

  ICES J. mar. Sci. 50:169-186.

⁸  National Marine Fisheries Service (2002). Endangered Species Act – Section 7 Consultation  Biological Opinion (PDF). Retrieved on October 5, 2006 at http://www.nmfs.noaa.gov/pr/redirect.htm

9  American Cetacean Society Fact Sheet ( 2004) retrieved on October 6, 2006 at
http://www.acsonline.org/factpack/bluewhl.htm

¹⁰   Blue whales. retrieved on October 7, 2006 at                 http://www.wwf.org.uk/filelibrary/pdf/bluewhale.pdf

¹¹    Reeves, R. et.al, (1998) Recovery Plan for the Blue Whale (Balaenoptera  musculus) retrieved at www.nmfs.noaa.gov/pr/pdfs/recovery/whale_blue.pdf

¹²   The Blue Whale, Retrieved on October 1, 2006 at

    http:// www.whales-online.net/eng/2/2-6-3.html