Estimating the abundance of narwhals is difficult due to the remoteness and large size of their distribution area, the mobility of the animals, and their close association with sea ice. Aerial surveys are most commonly used, but the results obtained must be corrected for both whales that are at the surface but missed by observers, plus those that are below the surface out of sight when the survey airplane is overhead. Another problem is that direct comparisons between surveys are not always possible, since surveys rarely have the same timing or cover the same area.
A rough estimate for the total world population is 85,000 animals (White 2012): A more detailed breakdown of the population status in different areas of the Arctic is given below.
Summer and winter distribution of narwhal stocks in Canada, West Greenland and East Greenland. Solid colours show summer distribution, hatched areas are winter distribution.
Narwhals are found off West Greenland at all times of the year. During the summer there are concentrations at Inglefield Bredning and farther south near the glacier fronts of Melville Bay. During the fall, winter and spring they are found in the ice pack of the West Greenland coast from Smith Sound to just south of Disko Bay (Heide-Jørgensen et al. 2010). While the summering aggregations are considered a stock for management purposes, at other times of the year narwhals off West Greenland are likely composed of a mixture of narwhals from several summering areas (Heide-Jørgensen et al. 2012).
The summer concentrations at Inglefield Bredning and Melville Bay were most recently surveyed in 2007 (Heide-Jørgensen et al. 2010). The abundance estimate for Inglefield Bredning, corrected for perception and availability biases, was 8,368 (95% CI 5,209–13,442). This area has been surveyed several times since 1986 and the number of narwhals seems to vary greatly from year to year and even within a season. It is thought that narwhals using this area may also use areas farther north in Smith Sound when ice conditions make them available.
The corrected estimate for Melville Bay was 6,024 (95% CI 1,403–25,860). This was the first estimate of summering narwhals for this area. Most narwhals were found close to the glacier fronts which reach the sea throughout Melville Bay.
The wintering area in eastern Baffin Bay along the West Greenland coast was most recently surveyed in March-April 2006, as part of a long-term series of surveys conducted 7 times since 1981 (Heide-Jørgensen et al. 2010). The survey resulted in a corrected estimate of 7,819 narwhals (95% CI: 4,358–14,029). However the survey covered only a small part of the entire Baffin Bay overwintering area. Numbers here seem to fluctuate from year to year, probably because of annual variations in ice conditions in the area, as well as variations in the timing of seasonal migrations.
During the summer narwhals are found all along the East Greenland coast north of 66° N, and concentrations are found in Scoresby Sound (Ittoqqortormiit) and Kangerlussuaq (Heide-Jørgensen et al. 2010). Narwhal have a scattered distribution along the entire coast and periodically occupy many fjords in the area. Available information from satellite tracking of narwhal from Scoresby Sound suggest that these narwhals do not mix with those from other areas during the summer, and that they should therefore be considered a separate stock (NAMMCO 2013). The first comprehensive survey, carried out in 2008, resulted in a total corrected abundance estimate of 6,444 (95% CI: 2,504–16,575), of which over half was found in the Scoresby Sound area (Heide-Jørgensen et al. 2010).
A comprehensive survey with narwhals as the main target species was carried out in Canadian waters in August 2013. The survey covered all major known summer aggregation areas for Baffin Bay narwhal in Canada, including Peel Sound, Prince Regent Inlet, Admiralty Inlet, Eclipse Sound and the East Baffin Coast. Jones Sound and Smith Sound were surveyed for the first time. This was the largest aerial survey ever carried out in Canada, with three planes and 15 observers taking part over a four week period. It is also the first time that all major narwhal habitat has been surveyed in a single year. It is expected that results from this survey will become available sometime in 2014.
Two aerial surveys were completed in August 2010 to assess the summering stock of narwhals in Admiralty Inlet. The surveys used an adaptive sampling plan which combined visual line-transect sampling of the entire inlet and aerial photography of aggregations of more than 50 animals. The two surveys yielded estimates of 24,398 (CV 0.25) and 13,729 (CV=0.40) narwhals. The differences between the two survey estimates are likely due to sampling variation related to survey coverage, sea state and animal movement. Combining the estimates from the two surveys using an effort weighted mean yielded a final Admiralty Inlet narwhal estimate of 18,049 (95% C.I. 11,613-28,053) (NAMMCO 2013, DFO 2012a).
Earlier surveys to estimate population numbers across Nunavut were carried out in the summers of 2002 to 2004. The Table below shows the results obtained (Richard et al. 2010).
Canada sets harvest levels for narwhals using a “Precautionary Approach Framework” (DFO 2008), which takes a conservative approach to management. As part of this approach, the Potential Biological Removal (PBR) method is used to determine the Total Allowable Harvest. This method was developed in the United States for the regulation of human-induced mortality on marine mammals, and produces a single threshold value for removals from a population, which allows depleted stocks to grow and other stocks to maintain their numbers.
The method produces a total allowable landed catch (TALC) for a narwhal stock, which takes into account whales that are struck and lost by hunters. Hunt loss corrections are derived from annual reports of landed and lost whales from communities under Community Based Management (DFO 2008).
For Baffin communities, present harvests are well below the recommended TALCs (DFO 2012c).
The most recent survey for narwhals in northern Hudson Bay was conducted in 2011, and resulted in an estimate of 12,485 narwhals (95% C.I. 7,515 - 20,743)( Asselin et al. 2011).
Virtually nothing is known about the size of the narwhal stock that periodically inhabits parts of Svalbard and areas farther to the east. As this stock has not been hunted for many years, it is likely stable in numbers.
Approximate summer distribution of narwhals in the Northeast Atlantic.The location of wintering grounds are not known in this area. Narwhals are rare east of Novaya Zemlya.