Balaena mysticetus

Bowhead Whale

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Bowhead Whale Bowhead Whale

 

Description

The bowhead whale (Balaena mysticetus) is a baleen whale of the right whale family Balaenidae in suborder Mysticeti. A stocky dark-colored whale without a dorsal fin, it can grow to 20 m (66 ft) in length. This thick-bodied species can weigh 75 tonnes (74 long tons; 83 short tons) to 100 tonnes (98 long tons; 110 short tons),[3] second only to the blue whale, although the bowhead's maximum length is less than several other whales

 

Geography

Bowhead whales are found only in Arctic and subarctic regions. They spend much of their lives in and near the pack ice, migrating to the high Arctic in summer, and retreating southward in winter with the advancing ice edge (Moore and Reeves 1993).

The International Whaling Commission recognises five stocks: Bering-Chukchi-Beaufort Seas (US (Alaska), Canada, and Russian Federation); Hudson Bay-Foxe Basin (Canada); Davis Strait-Baffin Bay (Denmark (Greenland) and Canada); Svalbard-Barents Sea (Spitsbergen) (Denmark (Greenland), Norway, and Russian Federation); and the Okhotsk Sea (Russian Federation and Japan) (Rugh et al. 2003).

The Bering-Chukchi-Beaufort Seas stock occurs from Chaunskaya Guba (Russian Federation) in the western Chukchi Sea east to Amundsen Gulf (Canada), and the northern Bering Sea south to Karaginskiy Zaliv (Russian Federation), St. Matthew Island, and Norton Sound (US (Alaska)) (Rice 1998).

Recent evidence of movements of tagged whales indicating overlapping ranges, and inconclusive analyses of genetic differences, have called into doubt the traditional distinction between the Hudson Bay-Foxe Basin and the Davis Strait-Baffin Bay stocks (Heide-Jørgensen et al. 2006, IWC 2007).

The range of the Hudson Bay-Foxe Basin stock was traditionally taken to include northern Hudson Bay, Hudson Strait, Foxe Channel and Foxe Basin. Tracking of satellite-tagged whales in 2002 and 2003 confirm movement from Foxe Basin through Fury and Hecla Strait into the Gulf of Boothia and Prince Regent Inlet (Cosens 2004).

The Baffin Bay-Davis Strait stock is centred in summer in the eastern Canadian High Arctic archipelago and along eastern Baffin Island. The whales move out of the summering areas as ice forms in autumn to wintering areas in polynyas (Holst and Stirling 1999), unconsolidated pack ice, and open water near the ice edge off West Greenland (Reeves and Heide-Jørgensen 1996) and eastern Baffin Island. The summering grounds include Cumberland Sound, the well-studied late summer and autumn feeding ground in Isabella Bay (Finley 1990), Lancaster Sound, Admiralty Inlet, and Eclipse Sound.

Animals satellite-tagged in Cumberland Sound in southeast Baffin Island in 2004 and 2005 moved into Prince Regent Inlet and the Gulf of Boothia and also into Foxe Basin and the Hudson Strait (Dueck et al. 2006). Animals tagged in West Greenland also moved to Prince Regent Inlet and Hudson Strait. There is thus no clear geographical division between the two putative stocks. The genetic evidence is inconclusive, and the IWC Scientific Committee currently regards the stock identity question as open (IWC 2007).

The Svalbard-Barents Sea (Spitsbergen) stock (see separate listing) occurs from the east coast of Greenland across the Greenland Sea, the Barents Sea and the Kara Sea as far as Severnaya Zemlya (Russian Federation), and as far south as the ice front, exceptionally reaching Iceland and the coast of Finnmark (Norway).

The Okhotsk Sea stock (see separate listing) occurs in the Sea of Okhotsk from Shantarskiye Zaliv east to Zaliv Shelikova, Gizhiginskaya Guba and Penzhinskaya Guba (Moore and Reeves 1993, Rice 1998).

Ecosystem

The seasonal distribution is strongly influenced by pack ice (Moore and Reeves 1993). During the winter bowhead whales occur in areas near the ice edge, in polynyas, and in areas of unconsolidated pack ice. During the spring these whales use leads and cracks in the ice to penetrate areas that were inaccessible during the winter due to heavy ice coverage. During the summer and autumn they concentrate in areas where zooplankton production is high or where large-scale biophysical processes create local concentrations of calanoid copepods (Finley 1990, Finley et al. 1998).

Small to medium-sized crustaceans, especially krill and copepods, form the bulk of the bowhead's diet (Lowry et al. 2004). They also feed on mysids and gammarid amphipods, and the diet includes at least 60 species. Bowheads skim feed at the surface and feed in the water column. It has recently been suggested that they also feed near the bottom, but probably do not directly ingest sediments as gray whales routinely do.

Conservation

Primary conservation efforts for Balaena mysticetus involve reducing or ending the hunting of this species. Agencies who are playing parts in the conservation of the species are the Alaskan Eskimo Whaling Commission (AEWC) and the National Oceanic and Atmospheric Administration (NOAA) (Shelden and Rugh 1995). Native people have been allowed to take only one whale every two years (Nicklen 2000). Whale populations plummeted as a result of a huge expansion in the whaling industry from the 1600s to the early 1900s (Shelden and Rugh 1995).

 

Threats

Heavy commercial hunting, beginning in the 1500s, depleted all populations of bowheads. The Bering-Chukchi-Beaufort Seas stock has recovered substantially since the end of commercial whaling in the early 20th century, while recent provisional estimates of the Hudson Bay-Foxe Basin and Baffin Bay-Davis Strait stocks also suggest significant recovery. There is no reliable evidence of recovery of the Svalbard-Barents Sea (Spitsbergen) and Okhotsk Sea stocks.

Limited aboriginal subsistence whaling on the BCB stock (by native peoples of Alaska, and the Russian Federation (Chukotka) is permitted by the IWC on the basis of advice from its Scientific Committee (most recently under its new aboriginal subsistence whaling management procedure). These takes have not impeded the recovery of the stock. Very small takes by aboriginal hunters are allowed in Canadian waters. So far these have been too few to impede recovery of the stocks, but there will be pressure to increase take levels given the recent, higher population estimates in the eastern Canadian Arctic.

There has been concern since the 1970s that disturbance from oil and gas exploration and extraction activities in the Arctic region might affect bowhead whales. There is also evidence of incidental mortality and serious injury caused by entanglement in fishing gear and ship strikes (Philo et al. 1992, 1993; Finley 2000). Environmental threats, such as pollution (Bratton et al. 1993) and disturbance from tourist traffic (Finley 2000), may affect bowhead whales but the impacts have not yet been well characterized or quantified.

During this century, a profound reduction in the extent of sea ice in the Arctic is expected, and possibly a complete disappearance in summer, as mean Arctic temperatures rise faster than the global average (Anonymous 2005). The implications of this for bowhead whales are unclear but warrant monitoring.

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