Bowhead Whale

Other PEMT sensitivity layers in this region:
Polar Bear | Bowhead Whale | Beluga | Ringed Seal | Peary Caribou
Migratory Birds | Traditional Hunting | Oil Spill Sensitivity

Summer
Bowhead Whale - Summer

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Eastern Arctic

Valued Component Features

Key habitat

During June to September, bowhead whale summer distribution is primarily in the eastern Beaufort Sea where they form large loose aggregations offshore from approximately mid-August to late September (Hardwood and Smith 2002; Harwood et al. 2008). The aggregations form in traditional areas where oceanographic conditions favour the concentration of crustaceous zooplankton, their main prey item (Thomson et al. 1986). Key habitat areas include the Tuktoyaktuk Peninsula, the Amundsen Gulf, and the south and west coastal areas of Banks Island (COSEWIC 2005). Habitat requirements of bowhead whales in summer grounds largely depend on the distribution of main prey resources which can vary from year to year depending on temperature, salinity, light intensity and nutrient availability (Mackas et al. 1985). Whales can be found in deep (>200m) or shallow (<50m) waters depending on the summer month and the availability of food (Griffiths and Buchanan 1982, Richardson et al. 1985, Mate et al. 2000). The older, mature bowheads (including cows and calves) tend to be found in the further offshore feeding areas (e.g., off the Tuktoyaktuk Peninsula), whereas the sub adults tend to occur in feeding areas closer to shore (e.g., off the Yukon coast)(L. Harwood, pers. comm.).

Banks Island Coast and Amundsen Gulf

Banks Island Coast and Amundsen Gulf are the first summer areas bowhead reach after migrating through offshore routes of the Beaufort Sea (Fraker and Bockstoce 1980, COSEWIC 2005). Bowheads can reach the coastal waters of Bank Island and Amundsen Gulf as early as May (Branham et al. 1980). Although bowhead are more frequently seen in May near the Banks Island coast (Hazard and Cubbage 1982).

Bowheads are often seen in the Amundsen Gulf along King's Bay in late July and early August (Hazard and Cubbage 1982). The western half of Amundsen Gulf are important summer grounds during July, where bowhead take advantage of early ice break up in these areas and forage in deep waters (>200 m) (COSEWIC 2005).

Tuktoyaktuk Peninsula

Areas north of the Tuktoyaktuk Peninsula are important summer areas in late August and September (Hardwood and Borstad 1986, Richardson et al. 1987, Dickens et al. 1987) where whales have been observed feeding off the shore of the Peninsula (Würsig et al. 1989).

The Kugmallit Canyon, and Tuktoyaktuk Peninsula inner and outer shelves are considered sensitive habitat areas for bowhead whale in the southeastern Beaufort Sea.

Mackenzie River Plume

The influence of freshwater into the Beaufort Sea creates nutrient rich environmental conditions ideal for foraging bowhead whales. Areas off King Point, Shingle Point, Mackenzie Bay and Herschel Island have all been identified as important bowhead whale habitat (WMAC 2000a, WMAC 2000b, WMAC 2000c, Dickens et al. 1987).

Bowhead use areas around the Mackenzie Delta in late summer . Distribution in the Mackenzie Delta can vary from year to year where in some years whales stick to shallow ice-free waters and in other years they are found offshore either in or near ice (Richardson et al. 1987).

In late August and September bowhead congregate around the Mackenzie River plume, where turbid, brackish water from active surface circulation and upwellings likely create nutrient rich environments for invertebrate prey species (Hardwood and Borstad 1986, Würsig et al. 1989).

Between August and October bowhead have been seen near Herschel Bay as they slowly make their fall migration back to the Bering Sea (Hardwood and Borstad 1986, Richardson et al. 1987).

Herschel Island, Komakuk area, Mackenzie Canyon and the shelf break north of Herschel Island are all ranked sensitive for bowhead whale.

Rationale for Selection

Historically, the bowhead whale was a very important resource to the Inuit, aiding in survival by providing a year's worth of food, oil and building material for an entire camp from a single whale (NWMB 2000). Archaeological records indicate that bowhead whales have been hunted in the Canadian Arctic since 1100 A.D. (Freeman et al. 1998). In the NWT, the Inuvialuit Settlement Region is currently allowed to harvest one bowhead whale annually. Current hunting of bowhead    whales by Inuit is more of a cultural and traditional importance rather than a food source. The bowhead whale hunt is viewed as a vital element to Inuit culture and the passage of traditional knowledge (NWMB 2000).

Other reasons for its selection include the importance of the Beaufort Sea to the bowhead whale's life history. Federally, the Bering-Chukchi-Beaufort bowhead whale population is listed as Special Concern in Canada (COSEWIC 2005) and lower risk/conservation-dependent by the World Conservation Union (IUCN). Due to commercial hunting pressures in the past, the bowhead whale was almost hunted to extinction (COSEWIC 2005). The Bering-Chukchi-Beaufort population has recovered from these detrimental levels but continued monitoring of the species is needed. Additionally, bowhead whales are an important component to the ecological functions in the Arctic seas both as predator and prey. Bowhead whale appear to be closely tied to the distribution of their prey (Würsig et al. 1989, Treacy et al. 2006) and could be a good indicator of ecological changes in the Beaufort Sea dynamics.

Sustainability

The Bering-Chukchi-Beaufort population had almost been hunted to extinction in the mid-19th century due to commercial whaling pressures. This population is not yet secure and currently is at about 50% of its historical population size and has increase 3.4% from 1978-2001 (George et al. 2004, COSEWIC 2005). The most recent documented population estimate is 10,740 (George et al. 2004). Regulation of commercial whaling is an important component in the sustainability of bowhead whales. Due to the late age of sexual maturity and low fecundity of this species, removal of individuals in the population can have significant effects on the population (COSEWIC 2005).

Historical sightings of bowhead whale in the Beaufort Sea indicate the importance of this area for spring, summer and fall migration periods. Predation, offshore human activity and climatic pressures that influence ice conditions all have the potential to affect the survival and distribution of the bowhead whale in the Beaufort Sea (COSEWIC 2005). Conservation of high use feeding areas within the Beaufort Sea is an important component in sustaining viable populations of this species as the distribution of bowhead whale appears to be closely linked to vertical and horizontal distribution of prey (Würsig et al. 1989).

Susceptibility to development

Potential implications of industrial development on bowhead whales in the Beaufort Sea include:

  • industrial activities may reduce the quality and amount of suitable habitat available to bowhead whales, especially for feeding
  • industrial activities may increase the risk of mortality to individual bowhead whales in proximity to developments
  • industrial activities may cause disruption of migration patterns and behaviour making whales more susceptible to other environmental pressures such as predation and climatic change

Habitat Susceptibility

Due to the occurrence of bowhead whale in the Beaufort Sea from spring to fall, they are susceptible to habitat impacts from industrial activities throughout most of the year in the Beaufort Sea. Residual effects from industrial activity may result in either complete loss of habitat, as is common with the ‘footprint' of industrial developments, or effective habitat loss, whereby bowhead whales avoid habitat in proximity to development.

Development activities to which bowhead whales may be susceptible include:

  • industrial pollution and miscellaneous spills
  • noise due to seismic activities and vessel movement
  • injuries due to marine vessel collisions
  • island building or temporary drilling platforms

Industrial pollution and miscellaneous spills that are discharged have the potential to result in either complete or effective habitat loss. Bowhead whale habitats most susceptible to these releases are the shallow waters in the Mackenzie Delta and Amundsen Gulf. The population impacts that may result from an oil spill would depend largely on the season, amount and type of contaminants released, climatic factors and response initiated. An oil spill within the shallow waters and river estuaries identified as important bowhead whale habitat would be the most sensitive and could produce major site-specific impacts. Areas around the Mackenzie River plume would be vulnerable due to the large number of whales that congregate in the area in late summer. An oil spill further offshore within the feeding, movement and migratory areas and corridors may produce fewer impacts because they can navigate around the spill in these greater water depths. Contact with spilled oil may directly affect the availability of invertebrate food and therefore the health and migratory behaviour of whales.

Man-made noise pollution in the Beaufort Sea may have detrimental effects on this species. Bowhead whale are sensitive to human noise created by drilling, marine construction, seismic exploration, and ships causing changes in normal behavioural patterns and in some cases avoidance of areas with activity (Richardson et al. 1986, 1990, 1995, Davies 1997). Presence of drilling rigs can create a significant temporary loss of available habitat (Schick and Urban 2000). Long-term effects of noise pollution on bowhead whales in the Beaufort Sea are unknown; although it is considered a high threat to bowheads in the eastern arctic (Moshenko et al. 2003).

Mortality Susceptibility

In addition to noise generation, marine vessels have the potential to collide with bowhead whales resulting in severe injuries. Collision with vessels can create large lacerations (George et al. 1994), which can affect the health of an individual whale directly and indirectly through alterations to feeding and other survival behaviour. George et al. (1994) found that vessel-inflicted injuries where low at approximately 1% in the Bering-Chukchi-Beaufort Sea stock. This could be correlated to the low rate of vessels in the area (George et al. 2004); however, similar to right whales, it may also be due low survival rates of those whales that have collided with vessels (Kraus 1990).

Mitigation

There are several strategies that can be applied to project-specific mitigation planning, based on the summary of project specific residual effects, the seasonality of bowhead whale movements, and the criteria used to define the grid rating. These considerations should not be interpreted as a prescription for actions imminently required; rather, they are strategies that may be valuable in project planning.

  • High quality foraging areas are key areas that are important to the viability of the species, and therefore impacts here should be mitigated and/or avoided where possible. These areas include Mackenzie Bay and the Tuktoyaktuk Peninsula. Should development be initiated in such areas, timing should attempt to coincide with periods when bowheads are not present (from September to April).
  • In areas of bowhead spring and fall migration, marine vessel movement activities within these areas should be limited to levels to which the population-level impacts are not apparent.
  • On-ice activities are generally unlikely to produce residual effects beyond the frozen water season, and may be a preferable option to open water activities, especially if accidents and hazards are controlled.

Climate Change

Global circulation models predict substantial decreases in both thickness and coverage of arctic sea ice due to increased atmospheric CO2. Present climate models are insufficient to predict regional ice dynamics, winds, mesoscale features, and mechanisms of nutrient resupply, which must be known to predict productivity and trophic response (Tynan and DeMaster 1997). However, we can speculate on the potential impacts of observed trends in Arctic climate on wildlife. Changes in the extent and concentration of sea ice may alter the seasonal distributions, geographic ranges, patterns of migration, nutritional status, reproductive success, and the abundance and structure of some species. For bowhead whale, like most cetaceans, decreases in ice extent will be more of an indirect effect than actual loss of habitat (Tynan and DeMaster 1997). One of these indirect effects include the potential change in abundance and distribution of marine invertebrates the bowhead whales food source.

Ice algae are an important component in the Arctic environment being the primary source in the food chain (Alexander 1995). Formed at the ice-seawater boundary, this ice algae forms on the underside of the ice and becomes part of the water column during spring melt. The presence of this new food source in the water column in spring creates a bloom of phytoplankton, where copedpods (the primary prey of bowhead whales) thrive (Drolet et al. 1991, Tynan and DeMaster 1997). Therefore, ice edge habitat is a very important component to bowhead whales. Change in the timing or loss of this spring food source could result in a shift of behaviour, migration patterns, distribution and survival of bowhead whales (COSEWIC 2005).

Sensitivity layers and scores

From April to June the majority of this population migrate towards summer areas in the eastern Beaufort Sea, following ice leads and open water areas that develop as a result of spring ice break up. Bowhead whale summer distribution is primarily in the eastern Beaufort Sea where they form large loose aggregations offshore from approximately mid August to late September (Figure 7). Data sets on bowhead distribution from 1980-1986 and from more recent surveys in 2007-2008 have been used to derive this sensitivity map (Harwood, pers. comm.). Observed bowhead densities have been calculated for 20 km x 20 km grid cells, and grid cells with >5 bowheads/100 km2 have been designated as aggregation areas according to DFO's present working definition (Harwood et al. 2008).

The number of times that bowheads aggregated in a given grid cell have been tallied over the available survey years, with the frequency of aggregations being used to designate a sensitivity of 3, 4 or 5. The rating system below was based on the period that bowhead whales are present and use the areas for feeding as well as for movement and migration. Potential residual effects from development would be most detrimental to the viability of the population in congregation areas and areas where upwelling provides quality foraging habitat for theses activities. Thus, higher risk categories are associated with these important habitats.

Summer/fall (May-October) Sensitivity

Low sensitivity (1): All non-aggregation areas shallower than 2 m, as bowheads cannot access such depths given their body size.

Low/Moderate Sensitivity (2): All non-aggregation areas deeper than 2 m, i.e., those areas that have limited use as movement/migration corridors and/or foraging areas

Moderate Sensitivity (3): Areas around the Mackenzie Delta in late summer. Distribution in the Mackenzie Delta can vary from year to year where in some years whales stick to shallow ice-free waters and in other years they are found offshore either in or near ice

Moderate/High Sensitivity (4): Western half of Amundsen Gulf are important summer grounds during July, and areas off King Point, Shingle Point, Mackenzie Bay and Herschel Island have all been identified as important bowhead whale habitat.

High Sensitivity (5): Areas north of the Tuktoyaktuk Peninsula are important summer areas in late August and September

Summary

The bowhead whale was largely selected as a VEC due to it is of cultural importance and traditional use to Inuit hunters. They are an important component to the ecological functions in the arctic sea, and are closely tied to invertebrate prey distributions making them a potentially good indicator of ecological changes in the Beaufort Sea dynamics.

Bowhead whales are present in the study area from spring to fall, with summer distribution primarily in the eastern Beaufort Sea. Key habitat areas include the west coastal areas of Banks Island, the Amundsen Gulf, the Tuktoyaktuk Peninsula, and the Mackenzie River Delta (COSEWIC 2005). Feeding is the predominant activity of bowhead whales in the Beaufort Sea. The bowhead whale's migration route in the Beaufort Sea follows leads in the ice where open water areas develop as a result of spring ice break up. Therefore, climatic changes have the potential to effect migration patterns, food abundance and survival of bowhead whales in the Beaufort Sea.

Potential impacts from industrial activity include pollution, miscellaneous spills, man-made noise impacts, and marine vessel collisions. Industrial activities occur during the winter season (i.e., in frozen water periods throughout much of the study area) are unlikely to result in direct impacts to bowhead whales as they winter in the Bering Sea. Industrial development during spring, summer and fall have the potential to impact bowhead whales depending on the location of these activities in the Beaufort Sea.

References

See references used for Bowhead Whale information.