Estimating the abundance of beluga is difficult due to the remoteness and large size of their distribution area and the mobility of the animals. Aerial surveys are most commonly used, but the results obtained must be corrected for both whales at the surface 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.
Beluga distribution in the eastern Atlantic. Summering areas in black and wintering areas are grey.
One estimate, made in 1939, gave a population of 40,000 to 50,000 beluga in the Barents, Kara and Laptev Seas (Svalbard and Karskaya populations; Boltunov and Belikov 2002). These numbers are very rough, and were based on observations of beluga during mass inshore movements in the fall. Another estimate made later guessed that from 15,000 to 20,000 beluga inhabited the White, Barents and Kara Seas (Boltunov and Belikov 2002).
Beluga distribution in the western Atlantic.
The size of this population had not been estimated before the early 1970s. The first reconnaissance survey at that time, of concentrations of belugas in estuaries, gave a very rough estimate of 10,000 belugas (Koski et al. 2002). Surveys conducted in the late 1970s estimated that 10,250 to 12,000 belugas were involved in the fall migration out of the central Arctic (Koski et al. 2002). A survey in 1996 estimated 21,213 belugas (95% CI 10,985 to 32,619) in the waters surrounding Somerset Island: Barrow Strait, Peel Sound and Prince Regent Inlet (Innes et al. 2002a). This estimate takes into account both whales missed by observers and those that might be unseen due to diving behaviour.
Any apparent trends of increase or decline in this population are difficult to assess since the confidence intervals for all estimates are quite large. In addition, some proportion of these animals winter off West Greenland, an area where a decline in numbers has been observed (see below). Though beluga here were subject to commercial hunting in the past, hunting pressure today in Canada on these animals is low (NAMMCO 2000), but is higher for those beluga which migrate to Greenland.
While direct harvest is low in the Canadian High Arctic, a component of this stock is subject to harvest off West Greenland during the fall migration, and in northern Greenland during the summer. There is evidence that the stock that winters in West Greenland is severely depleted (see below). However there is no evidence from surveys conducted in the Canadian High Arctic that the number of beluga occupying this area has declined (Innes et al. 2002a, Koski et al. 2002). More information is needed about stock structure in this area.
Aerial surveys flown in west Greenland between 1981 and 1994 found that beluga numbers decreased by 62% during that period, probably because of over-harvesting (Heide-Jørgensen and Reeves 1996). Further surveys in 1998 and 1999 confirmed the decline and found 7,941 (95% CI: 3650–17,278) belugas in West Greenland, including whales missed by the observers and whales that were submerged during the survey (Heide-Jørgensen and Acquarone 2002). New management measures (see below) may have reversed the decline, and the most recent survey carried out in 2006 revealed an abundance of 10,595 (95% CI: 4,904–24,650) (NAMMCO 2010).
Ungava Bay was formerly a summering area for beluga, but these appear to have been largely extirpated by past commercial and subsistence over-harvesting. Only very small numbers of belugas are observed there now, and the present summer stock size is thought to be fewer than 50 animals (Doniol-Valcroze and Hammill 2011) These animals may be remnants of the former stock, or transient or re-colonising animals (NAMMCO 2000).
Although there is some uncertainty in the available data, it seems that this population has declined from about 4,000 whales in 1985 to 2,000 in 2001. Although recent management measures may have stabilized the population and even allowed some increase, it is still highly vulnerable to decline at current harvest levels (Doniol-Valcroze et al. 2011).
James Bay also has a large summering population, probably exceeding 10,000 animals (DFO 2002c). Recent research has shown that at least some beluga are resident in James Bay year-round (Balleul et al. 2012). Belugas are not hunted in this area, however they may be subject to exploitation elsewhere (de March and Postma 2003).
Western Hudson Bay has a large number of summer resident beluga. A partial survey in 1987 reported 25,100 beluga (95% CI 18,300 to 52,800) (NAMMCO 2000), while a more complete survey conducted in 2004 estimated 57,300 (95% CI 37,700 to 87,100) (Richard 2005). Harvest of this group is estimated to be from 130 to 200 animals a year, which is likely a sustainable number for such a large group (NAMMCO 2000).
The most recent survey, conducted in 1999, found a stock size of 1,547 (95% CI 1,187 – 1,970). This group is listed as “threatened” by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).
The original size of this stock is unknown, but it has been back calculated to be in the low thousands. It has been estimated that about 16,000 animals were taken from the population between 1870 and 1960 (Kingsley 2002). This harvest, which was for commercial products, to protect fisheries, and for recreation, was uncontrolled and led to serious depletion of the population. Studies in the early and mid 1970s found numbers in the low hundreds, and all hunting was prohibited in 1979 (Kingsley 2002). Presently the stock size is thought to be around 1,100 animals (Hammill et al. 2007, Kingsley 2002).
The population appears to have stabilized at a level that is depleted relative to the historical stock size, and the lack of further recovery is of concern (Hammill et al. 2007). Potential threats to this population include pollution (Hobbs et al. 2003) and anthropogenic noise (McQuinn et al. 2011). While some have postulated that there is a high rate of cancer in this population based on the examination of stranded carcasses (Martineau et al. 2002), this interpretation is controversial (Hammill et al. 2003). This population is classified as "threatened” by COSEWIC.