Updated: December 2016
The bowhead whale is a large baleen whale. A body mass of up to 100 tonnes and a length of up to 20 m make the bowhead whale one of the largest animals on the planet. Females are slightly larger than males. The bowhead whale has no dorsal fin unlike the majority of baleen whales. The disproportionally large head constitutes more than one-third of the entire length of the animal and the name bowhead is associated with the whale’s high, arched lower jaw that looks like an archer’s bow. The colour of the animal is predominately black with much of the chin and lower jaw being white. A row of pigmented spots is located on each side of the lower jaw. A light grey or whitish band around the peduncle in front of the fluke is seen in some (older) whales. The bowhead whale is the longest-living mammal on the planet; it can reach an impressive age of around 200 years.
Eastern Canada-West Greenland stock: ca 6,400; Spitzbergen stock: ca 100
Circumpolar Arctic and sub-Arctic waters. Two stocks inhabit the North Atlantic- one in Eastern Canada/West Greenland, and one in the Greenland Sea/Svalbard area.
Historically hunted by Inuit, and also a large commercial hunt. Small numbers taken by Inuit in Canada and Greenland.
Populations reduced by historical whaling, but the Eastern Canada-West Greenland stock is increasing, and new evidence shows possible increases in the Spitzbergen stock as well. Hunting is managed by DFO in Canada. Greenland obtains quotas from the IWC and gives additional regulations.
Latin: Balaenoptera physalus (Linnaeus, 1758)
Icelandic: Grænland hvalur
English: Bowhead whale, Greenland right whale or Arctic whale
Approximately 18 m long (can reach a length of 20 m) and a body mass of 70-100 tonnes. Females are larger than males
Up to ~200 years (George et al. 1999)
Bowhead whales are filter feeders. They feed by swimming slowly forward with their mouth wide open. The diet consists of zooplankton, mainly copepods
One calf every 3-4 years from 13-13.5 m of body length at around 25 years of age
The bowhead is an Arctic resident, living its whole life in Arctic or sub-Arctic waters. It is migratory, with a seasonal appearance in certain areas; migration is influenced by the distribution of sea ice
The bowhead whale belongs to the family Balaenidae and genus Balaena. Besides Balaena, Balaenidae consists of Eubalaena, where the three species of right whales belongs.
The bowhead whale is thick-bodied compared to other baleen whales. The head constitutes one third of the body length and the baleen plates are correspondingly longer. The skin is smooth, the back broad and there is no dorsal fin or dorsal hump. The paired blowholes are located on a distinct elevation called the crown. The eyes are located quite low on the sides of the head. Flippers are short and broad. Colouration is predominately black with the chin and lower jaw being white. A row of pigmented spots is located on each side of the lower jaw. In some (older) whales a light grey or whitish band around the peduncle in front of the fluke is seen. The amount of white on the fluke and tail increases with age. Older individuals can be whiter on the head and can be heavily scarred (Reeves and Leatherwood 1985). The blubber layer of the bowhead whale is thick ranging from 5.5 cm on the chin to 28 cm on the trunk (Haldiman and Tarpley 1993).
Adult bowhead whales measure 12 – 18 m in length with some individuals reaching lengths of ~20 m (Haldiman and Tarpley 1993). By calculating the volume and weight of water displaced by a model made to scale a bowhead whale ‘of typical proportions’ was estimated to have a mass of 75 tons (Reeves and Leatherwood 1985). Females are typically larger than males. The flippers are short and broad with lengths ranging from 97 cm – 304 cm. Fluke width averages 33% of body length (Haldiman and Tarpley 1993).
Bowhead whales are relatively slow swimmers. Their migratory speed has been reported at approximately 1.1– 2.5 m s-1, which is in the same range as the mean speed for balaenid whales when foraging at the surface (Simon et al. 2009, Heide-Jørgensen et al. 2006). Tracking of whales with satellite transmitters in West Greenland in winter has shown whales to travel fast through dense pack ice. Three whales (one male and two females) were shown to travel 1,730 – 5,888 kilometres during one month. The authors hypothesised that the bowhead whales have the potential to cross stock boundaries that were perhaps not anticipated when the boundaries were established (Heide-Jørgensen et al. 2006).
Watch drone video of bowhead whales
The large head of the bowhead whale, that comprises approximately one-third of its total body length, functions as an enormous feeding device. The impressive mouth gap is more than 4 m2. The mouth forms a gigantic filtering apparatus with baleen plates up to 4 m long (Simon et al. 2009).
When foraging, bowhead whales moves at very slow speeds, less than 1 m/s. Each foraging dive can amount to ~2000 tons of filtered water and prey. Bowheads are not deep divers. Simon et al. (2006) showed a maximum foraging dive depth of 127 m, and a mean dive time of 11-20 min per dive. The bowhead whale diet consists mainly of zooplankton, especially Calanus copepods and amphipods as well as other small crustaceans.
Sounds and Communication
Bowhead whales are highly vocal. They use both hearing and sounds for communication, socializing, foraging, navigation, and mate selection. Five species of baleen whales are known to produce songs: the bowhead whale, blue whale (Balaenoptera musculus), humpback whale (Megaptera novaeangliae), fin whale (Balaenoptera physalus) and minke whale (Balaenoptera acutorostrata). Bowhead whale singing is most intense in the breeding season but bowhead whales have also been reported singing in other seasons (Reese et al. 2001, Würsig and Clark, 1993).
Stafford et al. (2012) found bowhead whales in Fram Strait (between Greenland and Svalbard) to call or sing continuous from November 2008 through April 2009. More than 60 unique songs were recorded. Also, Johnson et al. (2014) found great variability in songs for bowhead whales from the Bering–Chukchi–Beaufort stock and that songs were shared among individuals.
Social and sexual behaviour
The bowhead whales are often segregated by size, sex, and reproductive state during migration and on their summering grounds. Population segregation may be related to predatory pressures, diving abilities and habitat partitioning (Finley 2001). There are different reports on the bowhead whales social organization relating to populations, sex of the animal, age, and whether females are traveling with a calf. Bowheads have been observed in great numbers e.g. in areas with plenty of food or when traveling between sites. However, whether or not they are gregarious animals as such is still an open question. Large aggregations of up to 20-60 animals have been observed along the east coast of Baffin Island and in the Beaufort Sea. In the Svalbard–Barents Sea stock only individuals or pairs have been observed. During migration, bowheads often travel singingly, in pairs or in small groups (Reeves and Leatherwood 1985).
Sexual interaction between bowhead whales have been observed during spring migration in the western Arctic but have also been observed in the fall for animals of the Bering Sea stock. For the EC–WG stock sexual behaviour have been reported in fall at Isabella Bay, North East Canada. Sexual activity can take place between pairs of whales but most often occurs in larger ’mating’ groups (Würsig and Clark 1993).
The bowhead whale is one of the stockiest whales of appearance. Compared to the fast fin whale, for example, the bowhead whale is a relatively slow swimmer. When swimming only the whales’ head and the rounded back are above the water surface. The bowhead whale has many structural similarities to the right whales. Two obvious characteristics distinguish them from each other; the bowhead whales higher arch of the upper jaw and the absence of bonnet callosities (bumps of hardened skin on the top of the rostrum)(Haldiman and Tarpley 1993). The bowhead whales’ two blowholes send a V-shaped blow several meters in the air when bowhead whale spout.
The bowhead whale is probably the longest living mammal on earth. It can reach an impressive age of more than 200 years. Oldest estimated individual was 211 years old (SE 35) and was from Alaska. It was estimated using aspartic acid racemization in the nucleus of the eye. Recoveries of traditional whale-hunting tools from some harvested whales also indicate life-spans in excess of 100 years of age (George et al. 1999).
Conception in bowhead whales is believed to occur around a mean date of 24th March (Reese et al. 2001, Heide-Jørgensen et al. 2007). Mean length of gestation in bowheads from the Bering–Chukchi–Beaufort Sea stock was estimated to 13.9 months with parturition likely to occur in May – June. Disko Bay in West Greenland is used as a spring feeding ground and probably also a mating ground for bowhead whales from Eastern Canada and West Greenland. Near-term pregnant females are observed but females here are rarely accompanied with calves. Parturition in this population thus likely occurs after the whales have visited Disko Bay in April – May, probably around the same period as the Bering–Chukchi–Beaufort Sea stock (Heide-Jørgensen et al. 2012a).
The estimated body length at sexual maturity for female bowhead whales is around 13 m (George et al., 2004, Heide-Jørgensen et al. 2012a) at an age of ~25 years (Rosa et al. 2013). Male bowhead whales reach sexual maturity at body lengths of >12.7m (O’Hara et al. 2002) and probably at around the same age as the females (Rosa et al. 2013).
Near-term foetuses have been measured to be 3.9-4.3 m long and lengths of small calves between 3.63 m and 4.29 m have been observed in May (See Koski et al. 1993). Lactation probably lasts a year (George et al. 1999). Average calving rate is assumed to be 3-4 years, it is unlikely to be less than 3 years (Koski et al. 1993).
The only known natural predator to the bowhead whale is the killer whale (Orcinus orca).
Distribution and Habitat
Bowhead whales are endemic to Arctic and subarctic waters. The bowhead whale is the only of the baleen whales found year round in the Arctic. The overall bowhead whale distribution spans approximately latitudes 54°N – 75°N in the North Pacific basin and 60°N – 85°N in the North Atlantic basin (Moore and Reeves, 1993). Four management stocks of bowhead whales occupy the Northern Pacific Ocean, the North West Atlantic Ocean and the North East Atlantic Ocean.
Distribution in the North Atlantic
Bowhead whale distribution in the Northwest Atlantic includes the western Arctic Canada from the Canadian high Arctic Archipelago to Hudson Bay in the South, Baffin Bay, Davis Strait, the West coast of Greenland (with a southernmost limit at approximately 66°N (Moore and Reeves, 1993)) and northern Greenland.
The population in the Northeast Atlantic is distributed from the Greenland Sea between East Greenland to the Barents and Kara seas and into the Russian Arctic.
Bowhead whales live in close association with sea ice. They are migratory of nature, generally migrating to the high Arctic in summer and moving southward in winter with the advancing ice edge. More on migration is found in the section North Atlantic stocks: Bowhead whale migration in the North Atlantic.
For management, at least four geographic stocks of bowhead whales are recognized. The stocks are geographically separated by landmasses or extensive sea ice. The stocks are:
- The Eastern Canada–West Greenland (EC–WG) stock (Frasier et al. 2015)
- The Svalbard–Barents Sea stock (or the Spitsbergen stock)
- The Bering–Chukchi–Beaufort Sea stock
- The Okhotsk Sea stock
The International Whaling Commission (IWC) operates with the EC–WG population as being two distinct stocks; the Hudson Bay–Foxe Basin stock and the Baffin Bay–Davis Strait stock. The reason behind the stock delineation was the separation of bowhead whale summering areas in Baffin Bay and Foxe Basin, and the assumption that baleen whales make seasonal north-south movements rather than east-west movements. Exchange between the bowhead whale summering populations was therefore considered unlikely. However, neither historic nor scientific evidence has been presented confirming the separation of these two stocks. On the contrary, scientific studies based on photographic evidence and satellite tracking have linked bowhead whales between West Greenland and the Hudson Strait (Heide-Jørgensen et al. 2006). Also genetic studies support a one-stock hypothesis for the EC–WG bowhead whale population. It has also been found that whales from the EC–WG population are genetically distinct from the more westerly Bering–Chukchi–Beaufort population (DFO 2015).
For management purposes, particularly in regard to establishing quotas for subsistence hunting, it is essential to know the stock structure of populations. The recognition of one stock of bowhead whales in Foxe Basin–Hudson Bay/Baffin Bay–Davis Strait has led to a shared quota for the stock instead of different quotas for each of the two areas (DFO 2009, 2015).
Bowhead whale migration in the North Atlantic
Migratory patterns of bowhead whales have been documented from aerial surveys, shore- and ship-based observations, telemetry studies, and from subsistence whaling activities. Bowhead whales from the EC–WG stock spend the winter in Hudson Strait, northern Hudson Bay, or along the pack-ice edge extending to coastal West Greenland. Bowhead whales may also be found in winter in the North Water and in polynyas along the east coast of Baffin Island. In spring, the whales are found along the West Greenland coast, primarily Disko Bay, in Hudson Strait, Cumberland Sound, and the entrance to Lancaster Sound. In spring the whales cross Baffin Bay from Disko Bay to Lancaster Sound. The whales stay within the high Canadian Arctic or along the east coast of Baffin Island in summer and early fall and winter in Hudson Strait or at the West Greenland coast (Heide-Jørgensen et al. 2006).
Recently a study showed overlap of the EC–WG stock and the Bering–Chukchi–Beaufort stock when two whales spent time in the same area in the Northwest Passage in the high Canadian Arctic (Heide-Jørgensen et al. 2012b). Sea ice in the Northwest Passage is thus perhaps no longer a physical barrier separating bowhead whales from the Pacific and Atlantic Oceans as previously assumed.
The Svalbard–Barents Sea stock, also called the Spitsbergen stock, is confined to the Northeast Atlantic from the Greenland Sea between East Greenland to the Barents and Kara Seas and into the Russian Arctic (Norwegian Polar Institute 2016). Little is known about the migratory behaviour of this small stock. A survey conducted in April 2006 found whales in Fram Strait between East Greenland and Svalbard, which is a wintering site for this population (Wiig et al. 2007). There have also been bowhead sightings from Spitsbergen fjords during summer. Historical records from whaling operations show that whales stay north and northwest of Spitsbergen in spring, and around Jan Mayen in the same seasons. Whales were also found in the Greenland Sea in May-June. The seasonal pattern for this population is “up-side-down” compared to other populations that travel north in summer and south in winter (Moore and Reeves 1993). In April 2010, a satellite transmitter was deployed on a female bowhead whale from the Svalbard–Barents Sea stock for the first time. The whale was tagged in Fram Strait where she initially remained before she began a southwest migration and stayed between ~70 ̊ and 73 ̊ N until the tag stopped continuous transmissions in late July. Data showed that the whale spent most of its time in waters close to the ice edge, over areas where the bottom slope was relatively steep. Data was also transmitted in winter, where positions from late November until late December 2010 showed that the whale was back in the North at about 80 ̊ N. The authors suggest that this stock overwinters at high-latitude locations and that the migratory pattern of this whale during summer is consistent with the patterns that early whalers described for bowhead whales in this region in the 16th and 17th centuries (Lydersen et al. 2012). A recent study proposes the Northeast Water Polynya (NEW) in the Greenland Sea to be one of the most important summering grounds for this stock (Boertmann et al. 2015).
Current Abundance and Trends
Abundance estimates of the North Atlantic bowhead whales have been estimated from aerial surveys using line transects, surveys from vessels, and from capture-mark-recapture studies. Canada and Greenland survey the utilized EC–WG stock and Greenland and Norway survey the Svalbard–Barents Sea stock.
In 1981, aerial surveys of the winter range of the EC–WG stock provided an estimate of total population abundance of 1,349 (95% CI 402-4,529) (Koski et al. 2006). Since then, surveys in Eastern Canadian and West Greenland waters suggested that there were at least hundreds of bowhead whales but the range of coverage was limited and important seasonal aggregations had been missed (see references in Frasier et al. 2015). In the early 2000s (2002-2004), aerial surveys of the EC–WG population in Canadian waters were conducted by the Department of Fisheries and Oceans Canada (DFO). Several statistical analyses suggested abundance estimates from 6,344 (95% CI = 3,119-12,906) – 14,400 (95%CI = 4,811-43,105) individuals (See references in Frasier et al. 2015). In August 2013, DFO conducted the High Arctic Cetacean Survey (HACS) to update previous abundance estimates for the EC–WG bowhead whale population. The survey achieved almost complete coverage of important summer aggregation areas. The fully corrected abundance estimate was 6,446 (CV 26%) (Doniol-Valcroze 2015). The estimates indicate that the EC–WG population has increased significantly since bowhead whales were first protected from commercial whaling in the 1930’s.
Until recently, the protected Svalbard–Barents Sea stock was believed to number in the tens (Lydersen et al. 2012). But, a recent study estimated an abundance of 102 (95 % CI 32–329) bowheads in the Northeast Water Polynya (NEW) in the Greenland Sea from an aerial survey, which indicates that this stock could be recovering (Boertmann et al. 2015).
Total abundance in the Northern Atlantic in 2016: ~8000 bowheads
Total abundance in 2016 of the North Atlantic bowhead whale stocks (the EC–WG stock and the Svalbard–Barents Sea stock) amounts to nearly 8,000 bowheads.
Based on Bayesian analyses of genetic capture-mark-recapture data Frasier et al. (2015) estimated a total abundance estimate of 7,660 (95% HDI 4,500-11,100) for the EC–WG bowhead whale population. The results are consistent with a population increase throughout the 19-year study period.
Also the Svalbard–Barents Sea bowhead whale stock show signs of an increasing population. An aerial survey conducted in summer 2009 estimated 102 (95 % CI 32-329) bowheads in the Northeast Water Polynya (NEW). This result showed the largest abundance of bowhead whales reported from the Greenland Sea since the whaling period and made the authors conclude that the NEW could be one of the most important summering grounds for the Svalbard–Barents Sea bowhead stock. The whales forage on calanoid copepods from the productive deep basins along the coast of Svalbard east of the NEW (Boertmann et al. 2015).
A case study: Increasing abundance of bowhead whales in West Greenland
A study in April 2006, showed a significant increase in the winter population abundance of bowhead whales on the former whaling grounds in West Greenland. The result was surprising, as the change in abundance couldn’t be explained by recent or rapid growth in population size. One hypothesis was that the population, which showed a higher abundance of mature females, had recently attained a certain threshold size elsewhere. The authors also augmented that a severe reduction in sea ice facilitated access to coastal areas, and that these two in combination could explain the increase in the occurrence of whales. Consequently, the survey documented the largest number of bowhead whales recorded for the past 100 years in West Greenland. This was a first clear indication that the population was increasing (Heide-Jørgensen et al. 2007). A recent study from 2015, however, indicates that the observed increase in abundance (between 1998 and 2006) has levelled off (Rekdal et al. 2015).
Bowhead whales have been protected since 1931 apart from limited subsistence whaling. The EC–WG stocks and the Bering–Chukchi–Beaufort stock are subject to subsistence whaling while the two other stocks are fully protected.
Three out of the four bowhead whale stocks seem to be increasing in abundance (see Table below). For the Okhotsk Sea, data is insufficient for estimating abundance but according to IWC the population appears small and is subject to both anthropogenic and natural pressures (IWC 2016a). IWC recommends that an abundance estimate be obtained for this population.
Abundance estimates, trends and current status from the International Union for Conservation of Nature, the IUCN Red List of Threatened Species (IUCN 2016), of the four bowhead whale stocks are summarized in the table below. The IUCN operates with a separate status for each of the four stocks.
Conservation Status according to other international organisations
The Convention on International Trade in Endangered Species of Wild Fauna and Flora CITES lists the bowhead whale as one mega-population grouping the four recognized populations in the Appendix I – ‘threatened with extinction’. CITES does not distinguish between the status of the different stocks. As is the case for the fin whale (see also fin whale – Stock status) pooling of different populations together under a single listing can be misleading as the stocks are by definition reproductively isolated and may have very different conservation histories. This is particularly dangerous when the populations pooled together are very different in size, as is the case for the EC–WG and Bering–Chukchi–Beaufort stocks that are much larger than the Svalbard–Barents Sea and Okhotsk Sea stocks (NAMMCO 2016).
In the North Atlantic, the bowhead whale is managed by two international management organisations, the North Atlantic Marine Mammal Commission (NAMMCO) and the IWC, for those countries that are members. Canadian takes are managed domestically.
Commercial bowhead whaling was prohibited in 1931. Canada and Greenland resumed hunting bowheads from the EC–WG stock in 1996 and 2008 as aboriginal subsistence whaling.
Management measures in NAMMCO member countries
The last updated list of laws and regulation in NAMMCO countries regarding hunting of marine mammals (a.o. protection and hunting methods) can be found here.
Hunting in Greenland is regulated and administered by the Ministry of Fisheries and Hunting (Government of Greenland 2016). Some of the regulations are general to hunting (Home Rule Act no. 12, 29-10-1999, and later amendments in 2001, 2003 and 2008), animal welfare (Home Rule Act no. 25, 18-12-2003), nature protection (Home Rule Act no. 29, 18-12-2003), hunting permits (Executive order nr. 20, 27-12-2003), while others address specifically the hunting of large whales. In addition to Greenland Government rules there may also be additional rules set by the municipality.
There is no private ownership of land, sea or living resources. Hunting grounds and game animals are open to harvest and use by Greenlandic citizens, subject to hunting licenses. However, only persons with a full-time occupational hunting license are allowed to hunt large whales, and there are a number of important conditions and limitations, including those related to catch limits, methods of hunting, training and reporting.
Locally, a team of wildlife officers/wardens control hunting and fishing activities, making sure that conservation measures of protected areas and species are observed, and passing on information to the local community. The wildlife officers work in close cooperation with the municipalities, the police, and the Government of Greenland.
The IWC determines the catch quotas for the bowhead whales taken in Greenland. The quota year for bowheads is from March 1st to December 31st.
Bowhead whales in Norway are fully protected. Whaling is under the authority of the Ministry of Trade, Industry and Fisheries (Government of Norway, 2016). Currently, the common minke whale (Balaenoptera acutorostrata) is the only legally hunted whale species in Norway.
Hunting and utilisation
Subsistence hunting for bowhead whales by Inuit in Canada, Greenland and Alaska are important for traditional food, economics and for sustaining cultural traditions and values. Although the bowhead whale populations have been protected since 1931, the Inuit in Canada, Greenland and Alaska can catch a limited number of whales as aboriginal subsistence whaling. The small number of whales hunted by Aboriginal people in Canada is managed domestically. Quotas for catches by Aboriginal people in Greenland and Alaska are set by the IWC (IWC 2016b). Inuit in Canada resumed bowhead whale hunting in 1996, and 24 bowhead whales have been taken in the period 1996-2014 (DFO 2015. Inuit in Greenland resumed bowhead whale hunting in 2008, and 8 bowhead whales have been taken in the period 2008-2015 (Government of Greenland 2016).
The bowhead whale was almost hunted to extinction by European and American commercial whalers through a nearly 400-year period between the 1500’s and the 1900’s. All stocks of bowhead whales were exploited. Currently of the two North Atlantic stocks, only the EC–WG stock is exploited while the Svalbard–Barents Sea stock is fully protected throughout its range. Both stocks are considered increasing, for more details see under Stock Status.
In Eastern Canada two Inuit communities, the Nunavut Settlement Area and the Nunavik Marine Region (northern Quebec) resumed subsistence hunts for bowhead whales in 1996 and in 2008, respectively. The hunts are co-managed by the Nunavut Wildlife Management Board, the Nunavik Marine Region Wildlife Board and Fisheries and Oceans Canada. Hunting is licensed by the DFO (DFO 2015). It has been estimated that the EC–WG bowhead whale population can support a total human-induced mortality of 52 whales annually resulting from all sources of anthropogenic mortality including hunt, struck and loss, net entanglements and ship collisions (Doniol-Valcroze 2015). The current annual level of total allowable hunt is five bowhead whales in Nunavut and two in Nunavik. It is prohibited to catch calves less than 7.6 m. in length and females accompanied by calves (DFO 2015). Table 2 lists the bowhead catches in Eastern Canada from 1996 – 2014, a total of 24 catches.
The West Greenland hunt for bowhead whales from the EC–WG stock resumed in 2008 under conditions established by the IWC (DFO 2015). In 2014, IWC re-approved the two strikes per year for West Greenland with the requirement for an annual review by the IWC Scientific Committee. The catch history of bowheads in West Greenland since 2008 is listed in table 3. The Government of Greenland allows for unused catches to be transferred to the following year.
Hunting methods in NAMMCO countries
’People’s right to hunt and utilize marine mammals is a firmly established principle in NAMMCO, and hunting conditions and techniques have always been priority issues. Embedded in this right is also an obligation to conduct the hunt in a sustainable way and in such a way that it minimizes animal suffering’ (NAMMCO 2010a).
Besides annual hunting quotas, a number of regulations have to be met for legal bowhead whale hunting in West Greenland. Only hunters with a valid full-time occupational hunting license, a species-specific license, an approved harpoon gun, and mandatory fishing gear are allowed to hunt bowheads. Furthermore, hunters have to have attended a course in the use of ‘whale-grenades’ to be allowed to buy and handle those grenades. The hunter that holds the bowhead-license also has to report his plans for the hunt of the bowhead whale to the authorities. The bowhead whale can only be hunted between March 1st and December 31st. Only adult whales can be taken and females with calves and calves are fully protected. The actual bowhead whale hunt requires three whale hunting boats of at least 11 meters. Mandatory hunting gear on the boats includes a harpoon gun (calibre of at least 50 millimetres with approved whale grenades for large whales) and a line or trawl winch with a tractive force of at least five tonnes. Furthermore, the boats have to be equipped with buoys that prevent the whale from sinking. A wounded bowhead whale has to be put down using a ‘whale-grenade’ shot to the breast-region.
Once killed, the whales have to be flensed at an authority-approved place. All parts of the whale have to be used. If there’s too much meat for the hunters themselves to use or sell, the leftovers must be given to the local community.
Furthermore, the catch has to be reported to the authorities before it can be sold, and a tissue sample has to be delivered to the local authority. There can also be regulations regarding where it is allowed to hunt whales and where only whale-safaris can take place (Government of Greenland 2016).
Past and Current harvest
A tragic whaling history
The need for blubber, meat, oil, bones, and baleen started the European’s hunt for whales in the Arctic region. The bowhead whale, a fat, slow swimmer that floats after death, was an ideal target for the European, and later American, whaling ships to exploit. This first or ‘traditional’ commercial whaling is distinct from ‘modern’ commercial whaling, which is characterized by fast, motorized vessels with harpoon guns. The exploitation of the bowhead whale precedes the era of modern commercial hunting, when it ended in the early 1900’s (Ross 1993).
Whaling for bowhead whales, or the Greenland whale, polar whale or simply whale as it was referred to at the time, began off the southern coast of Labrador around the year 1540. As the whaling for bowheads in this area levelled off towards termination in the early 1600’s, bowhead whaling started near Spitsbergen. The whaling activities continued and by the year 1700 it had expanded into the Davis Strait region and into the Hudson Bay in 1860. By the late 19th century, when whaling was in its last phase, whalers were hunting bowhead whales throughout the North Atlantic sector. In the 19th century, American whalers went for the bowhead whales in the Sea of Okhotsk and the Bering, Chukchi, and Beaufort seas (Ross 1993). The hunt for bowhead whales thus continued through almost four centuries at levels driving the bowhead stocks close to extinction.
Higdon (2010) revised previous harvest series and estimated the combined commercial and Inuit harvests in eastern Canada and West Greenland since 1530 AD to 70,000 landed whales. This estimate is without struck-and-lost animals. To maintain the overall killed whales struck-and-lost animals ought to be added (struck-and-lost rates of 15–20% has previously been used by Mitchell (1977)). Using the revised harvest series, Higdon (2010) suggests, will improve estimates of pre-exploitation population size over previous attempts by Mitchell and Reeves (1981), Mitchell (1977), and Woodby and Botkin (1993).
In 1931, the League of Nations Convention protected the bowhead whale from commercial whaling. Some limited subsistence whaling still occurred by Inuit in Alaska. In 1946, the IWC was established by the International Convention for the Regulation of Whaling. IWC continued the prohibition on commercial whaling started in 1931 and began to regulate commercial whaling among signatory nations in 1964. In 1977, IWC called for a ban on the increasing subsistence bowhead whaling in Alaska due to concerns about the status of the whale populations. A ban was not implemented but the IWC granted a limited quota (Reeves and Leatherwood 1985).
Stock sizes prior to commercial whaling
Estimation of pre-exploitation stock sizes of bowhead whales have been attempted several times using historical records and population models, often in combination. However, such estimation is a difficult exercise because of lack of both a complete catch record and of basic information on biological parameters. Here pre-exploitation stock size estimates from Woodby and Botkin (1993) are presented. The estimated stock sizes are calculated by extrapolations from catch data. For full methodology see Woodby and Botkin (1993). The Spitsbergen pre-exploitation stock size was estimated to 25,000, Davis Strait to 11,000, Hudson Bay to 575, Bering Sea to 18,000 and the Okhotsk Sea to 6,500. In 2006, Allen and Keay reconstructed the Greenland–Spitzbergen bowhead population throughout the period of commercial exploitation by European whaling vessels (1611 – 1911). The estimate of approximately 52,500 adult bowhead whales resident in the waters between the east coast of Greenland and Spitsbergen in 1611 was calculated using species-specific biological parameters, a delayed-difference recruitment model, and historical whaling records. The estimate of Allen and Keay (2006) was more than double of the previous estimate from Woodby and Botkin (1993). Also Higdon (2010) suggests that using his revised harvest series estimates of pre-exploitation population size would be improved over previous attempts.
These few examples give an idea of the complexity of estimating pre-exploitation stocks sizes of commercial harvested whales. Regardless of the exact size, there is no doubt that bowhead whales were numerous inhabitants of Arctic and sub-Arctic waters previous to the whaling era. The removal of that many large marine mammals in a fairly short time period must have had an enormous impact on the Arctic ecosystems as suggested by Allen and Keay (2006).
Acoustic pollution is one of the new ‘threats’ facing the bowhead whales. Anthropogenic noise in Arctic waters is increasing as human activity increases as a consequence of climate change. Lesser sea ice and an extended open-water season make exploration and exploitation for oil and gas possible as well as increased shipping and shipping routes in otherwise previous impassable regions is expected. Also noise from military activity (e.g. sonar), from helicopter- and airplanes, and from marine constructions add to the overall commotion in the previous sound-pristine Arctic waters.
As marine mammals rely heavily on both hearing and producing sounds for a number of vital behaviours like communication and navigation, prey detection, predator avoidance, and mate selection, increases in underwater sound levels of anthropogenic origin could affect these important life-history functions (Blackwell et al. 2015).
Blackwell et al. (2015) found that in proximity to seismic operations, bowhead whales on their westward autumn migration in the Alaskan Beaufort Sea decreased their calling rates and with sound levels above a certain threshold the whales were virtually silent. The effects on the animals of such a change in behavior are unknown.
CLIMATE CHANGE AND ANTHROPOGENIC IMPACTS
Reductions in sea ice as a consequence of climate change will likely have negative effects on some marine mammals, for example, seals that give birth to pups on ice. However, the reliance of the ice-associated whales, including the bowhead, on sea ice-mediated ecosystems is unclear (Laidre et al. 2008, Moore and Huntington 2008). Reductions in sea ice may actually enhance feeding opportunities for the bowheads on prey both produced in and/or advected to their summer and autumn habitats (Moore and Laidre 2006). Despite roughly two decades of sea ice loss in the Alaskan Beaufort Sea, the Bering–Chukchi–Beaufort population has increased steadily at a growth rate of 3.4% suggesting that sea ice reduction is not hindering recruitment to this population as it rebounds from overhunting by commercial whaling (George et al. 2004). Anticipated changes for the bowhead whale populations include migration alteration and occupation of new feeding areas (Moore and Huntington 2008).
Although bowhead whales may actually benefit from lesser sea ice through increased access to prey, the bowhead whales face a growing number of anthropogenic threats as the Arctic becomes more accessible for humans. The impact on bowhead populations of potential risks like oil spills, collisions with ships, increased ocean pollution, emissions from mining activities etc. remain, for now, uncertain.
Research in NAMMCO member countries
The bowhead whales are subject to extended research activities in both Greenland and Norway. Studies on photo identification (Heide-Jørgensen and Finley, 1991), satellite telemetry studies (Heide-Jørgensen et al. 2003, 2006, 2012a, Lydersen et al. 2012), acoustic studies (Stafford et al. 2012, Tervo 2009, 2011, 2012a,b), genetic studies (Borge et al. 2007, Rekdal et al. 2015, keane et al. 2015) and studies in age and reproduction (Heide-Jørgensen et al. 2012a) have expanded our knowledge on bowhead migration patterns, stock structure, behaviour and life-history. Surveys (Boertmann et al. 2015, Heide-Jørgensen et al. 2007, Wiig et al. 2007) have further added to this knowledge by estimations of abundance.
Rekdal et al. (2015) used two different methods for estimating abundance and trends of bowhead whales in Disko Bay, West Greenland: aerial survey and genetic capture-recapture approach. They found that the two abundance estimates were complementary. The aerial survey provided a snapshot that is useful for examining the local trend without dependence between years. The genetic capture-recapture approach estimates the size of the actual source population but this approach is less suited for time series estimates requiring samples over many years. The two approaches do not necessarily lead to identical estimates, but in combination they give valuable insight into trends affecting abundance and the fraction of the population that is present within the surveyed area (Rekdal et al. 2015).
Boertmann et al. (2015) took advantage of an aerial survey for walrus (Odobenus rosmarus) in part of the Northeast Water Polynya (NEW) and observed several bowhead whales, resulting in an abundance estimate of 102 (95 % CI 32–329) individuals. The otherwise fairly inaccessible area has only recently been visited by researchers. The authors concluded that the NEW might be one of the most important summering grounds for the Spitsbergen stock and that their results provides renewed hope for the Spitsbergen stock that until now has shown only inconclusive signs of recovery despite more than 100 years of protection from whaling (Boertmann et al. 2015).
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