Beluga whale (Delphinapterus leucas) COSEWIC assessment and status report: chapter 10
Population Sizes and Trends
- St. Lawrence Estuary Population
- Ungava Bay Population
- Eastern Hudson Bay Population
- Western Hudson Bay Population
- Eastern High Arctic – Baffin Bay Population
- Cumberland Sound Population
- Eastern Beaufort Sea Population
The Canadian populations of belugas have been a subject of conservation attention for some time (Table 1). All of the seven populations have received status designations from COSEWIC. Since the original COSEWIC population status assignments much research has been conducted, particularly to gain new information on their population size. Recent population estimates have contributed to several new population status reports produced by Department of Fisheries and Oceans Canada. Beluga populations are usually assessed by aerial surveys. Some estimates are not corrected for diving animals missed by the survey, and these will be substantial underestimates (a factor of very roughly two; National Marine Fisheries Service 2002).
|Stocks||Approximate current population size||Population size compared to original||Population growth trend|
|St. Lawrence||~952||Low||Stable or Increasing|
|Ungava Bay||< ~50||Low or extirpated||?|
|E Hudson Bay||~2 045||Low||Decreasing|
|W Hudson Bay||~50 000Footnote a||Large||?|
|Eastern High-Arctic - Baffin Bay||~21 213||?||?|
|Cumberland Sound||~1 547||Low||Increasing or stable|
|Eastern Beaufort Sea||~39 258Footnote a||Large||Increasing?|
The estimated numbers of mature animals (in Technical Summaries) are approximately 60% of these total estimates.
Surveys of this population have been conducted since 1973. Kingsley (1998) attempted to develop correction factors in order to compare results from 10 surveys carried out between 1973 and 1995. He concluded that the population had increased on average by 17 belugas per year (SE = 4) and that the 1995 index of abundance was 650 (SE = 40) belugas, possibly more than double some of the lower estimates made in the early 1980s (Pippard 1985). There remains considerable debate on whether the population is really showing a significant positive trend. Michaud and Béland (2001) have argued that only surveys since 1988 are comparable and that the apparent trend was not significantly different from that of a stable population. The most recent photographic aerial survey (Gosselin et al. 2001) analysis also has indicated no significant increase in numbers of belugas since 1988.
WhÎle aerial surveys provide an index of abundance, recent studies based on aerial photography (Sergeant and Hoek 1988, Kingsley 1996) and studies of diving behaviour, using telemetry, are providing means of correcting for animals which are missed during surveys because they are submerged (Martin and Smith 1992). In the St. Lawrence a different approach has been used to obtain a correction factor for submerged belugas. Groups were watched from a hovering helicopter and their disappearances and re-appearances were timed. Full-size and calf-size, white- and grey-coloured models of belugas, suspended at various depths, were also photographed and observed from the air. Results yielded a correction factor of +109% (Kingsley and Gauthier 2002). This is in the range of the various estimates for Arctic belugas (+75% to +100%) derived from satellite telemetry studies of their diving behaviour (Martin and Smith 1992, Heide-Jørgensen et al. 1998). It should be noted that the different methods might not produce exactly comparable correction factors because of the additional visual clues which might be present when viewing moving groups of live belugas from an aircraft.
Standardization of survey methods and periodic monitoring of this population in the future will probably result in good estimates of the population trend. Recent population estimates, corrected for submerged animals, were 1209 (SE=189) for 1997 (Kingsley and Gauthier 2002) and 952 (SE=16%) for 2000 (Gosselin et al. 2001).
Three aerial strip- or line-transect surveys, covering 25% of Ungava Bay each time, were flown in 1983, 1993 and 2001 (Smith and Hammill 1986, Kingsley 2000, Gosselin et al. 2002). No whales were seen on any of the transect lines in any of the surveys. Coastal reconnaissance surveys done in conjunction with the offshore transect surveys sighted very few belugas even in areas known for estuarine concentration such as the Mucalic, George and Whale Rivers. In the latest survey, no whales were seen even during the coastal reconnaissance flights.
It has been estimated that a minimum of 200 belugas would have to be present in Ungava Bay for them to be detectable on survey transects. From sightings made outside his line transects, Kingsley (2000) estimated the population in Ungava Bay could possibly be as large as 50 animals.
During the period 1980-2000, there has been a noticeable reduction in the median age of belugas taken by the Nunavik communities of northern Quebec, dropping from 14 years in the period 1980-87 to 9 years during 1993-99 (Lesage et al. 2001). For belugas caught by communities in Ungava Bay, the median age is even lower at 8.5 years.
The Inuit of Kangirsuk on the northeast coast of Ungava Bay indicate that there has been a decline in the number of belugas in their area. They are uncertain of the causes but mention increased noise disturbance as a probable factor.
All evidence indicates that the resident beluga population of Ungava Bay is very low if, in fact, it does still exist. No significant estuarine aggregations are presently known and observations made at the principal estuaries do not reveal any important concentrations of belugas during the summer months.
The impact of continued over-harvesting of the Eastern Hudson Bay population has been a major concern in recent years (Bourdages et al. 2002). The latest aerial surveys flown in the summer of 2001 (Gosselin et al. 2002) and reanalysis of a 1985 survey (Smith and Hammill 1986) indicate that the Eastern Hudson Bay population has declined by almost 50% since 1985. Readjusted abundance estimates for belugas, corrected for diving animals, were 3849, 2137, and 2453 for the years 1985, 1993 and 2001 respectively (Bourdages et al. 2002). When these estimates are used in population models, the median estimated population size in 2001 was 2045 beluga (Bourdages et al. 2002). Bourdages et al. (2002) estimated population trajectories until 2011 using various hunting scenarios and population models. If current harvest rates continue, five of their nine models predicted a greater than 95% probability of extirpation in 2011.
A Five Year Beluga Management Plan (Anon. 1996) was put into place recommending harvests of 90 animals in eastern Hudson Bay, 100 belugas in Hudson Strait, and 50 animals in Ungava Bay. It is now felt that the total allowable annual catch for Eastern Hudson Bay has been too high (DFO 2001) and has resulted in a continuing decline of the population. This is also supported by a significant decline in the mean age of the harvested animals (Lesage et al. 2001), and a marked decline in the number of animals observed in the main area of summer estuarine concentrations (Doidge 1994, Hammill 2001).
Management of the Eastern Hudson Bay belugas is complicated by the fact that an unknown proportion of this population is harvested in Hudson Strait during the spring and autumn migration. Recent genetic evidence shows that Eastern Hudson Bay belugas are taken in a significant proportion of the harvests of the Nunavut and Nunavik communities. The proportions are not yet well defined and more years of sampling are required to obtain meaningful estimates (de March and Postma 2003). Models incorporating the best estimates for harvests, including struck and lost whales, and population estimates for Eastern Hudson Bay conclude that the present annual removals will result in the disappearance of the Eastern Hudson Bay population in a relatively short time. Hammill (2001) calculated that a continuing present average harvest of 106 per year is too high (Lesage et al. 2001), and that a reduction to 40 annually would be sustainable. A more recent evaluation concluded that the total removals from the Eastern Hudson Bay population should be less than 20 belugas per year to allow some population recovery (Bourdages et al. 2002). Eastern Hudson Bay belugas are also taken in Hudson Strait, making the annual harvest from the Eastern Hudson Bay population difficult to control. One recommendation is a complete closure of hunting in Eastern Hudson Bay, and a reduction of harvest to 100 belugas annually in Hudson Strait, based on the present best estimates (19%) of the proportion of Eastern Hudson Bay belugas caught there (de March and Postma 2003).
A number of factors remain uncertain in the evaluation of harvesting impact on the Eastern Hudson Bay population. Improved estimates of total removals will require better data on hunting losses, more genetic sampling from Hudson Strait and other areas, and better harvest reporting. Improved estimates of total population size will also require refined correction factors for animals that are underwater during aerial surveys.
Abundance estimates of 1842, 3141 and 7901 belugas, uncorrected for submerged animals, have been derived for James Bay in 1985, 1993 and 2001 respectively, an area contiguous with the Eastern Hudson Bay population (Gosselin et al. 2002). The genetic affiliation of these belugas is not known since virtually no samples have yet been taken there. The apparent increase in numbers over the years of aerial surveys cannot be explained by population growth, but probably results from different survey coverage and seasonal movements of animals in and out of this area. No harvesting occurs in James Bay during the summer, but the contribution from this group to the spring and autumn harvests in other Nunavut and Nunavik communities must be considered in order to refine the management plans in the future.
The Inuit of Nunavik report that belugas have become scarce in certain areas. Belugas were once common along the coast and in small river mouths near Inukjuak (Elie Weetaltuk, pers com. 1983) and the Nastapoka River (Doidge et al. 2002). Other areas such as Salluit and the Great Whale River now have few whales. It is generally held that these changes are related to increased disturbance from motorboat traffic and commercial shipping, as well as over-harvesting (Doidge at al. 2002, McDonald et al. 2002).
No aerial surveys have been made of this population for over 15 years.Richard et al. (1990) and Richard (1993) estimated the size of this population, from surveys between 1978 and 1987, to be in excess of 23 000, with another 1 300 belugas along the south Hudson Bay - Ontario coastline, and some 700 animals in the Northern Hudson Bay area. None of these estimates were corrected for submerged whales so will be substantial underestimates.
Belugas in western Hudson Bay spend all of the summer months in shallow coastal areas. Results for four belugas, instrumented with telemetry tags, showed that they rarely exceed 40 meters in depth during their dives in August. They begin deep diving as soon as they start to migrate east in September (Martin et al. 2001). Since they remain in shallow water for the whole of the summer period, aerial survey correction factors, generally applicable to other deep-water Arctic beluga populations (Martin and Smith 1992, Heide-Jørgensen et al. 1998), might not be appropriate for this population. A larger proportion of Western Hudson Bay belugas in shallow water might be seen during surveys, but other factors such as turbidity and clumping might also influence the estimates.
In 2003 the hunt for members of the Western Hudson Bay Population was 502 for western Hudson Bay and southeast Baffin communities (S. Cosens, DFO Winnipeg pers. comm. 2004). To that should be added the number of western Hudson Bay whales taken in the Belcher Islands (Sanikiluaq); perhaps 88% of the 70 caught in 2003 were from the Western Hudson Bay Population, i.e. about 62, and the number of western Hudson Bay animals caught in the Hudson Strait from northern Quebec, about 200 (S. Cosens and P. Richard, DFO Winnipeg pers. comm. 2004). Thus the total catch in 2003 from the Western Hudson Bay Population was about 764, which is a considerable rise from levels in recent years, when there was a total catch of about 500 per year (S. Cosens and P. Richard, DFO Winnipeg pers. comm. 2004).
Recent aerial surveys of belugas occupying the Canadian High Arctic during the summer yield an estimate of abundance, corrected for submerged animals, of 21 213 (95% CI = 10 985 to 32 619) (Innes et al. 2002b). It is not possible to compare the results of this survey with previous ones (Smith et al. 1985), because the timing and area covered by the surveys were different. The detection of trends in abundance of belugas by aerial surveys of the Canadian high Arctic summer habitat will always remain problematical, because of the wide area of occupation by belugas, and the inter-annual differences in timing of ice break-up with its effect on the seasonal movements of belugas (Smith and Martin 1994, Richard et al. 2001a).
The summer harvest of belugas in the High Arctic totals less than 100 individuals a year (DFO 1999). Innes and Stewart (2002), in a modeling exercise, estimated that the number of belugas spending the summer in the High Arctic, and which also remained in the Baffin Bay – North Water area in the winter, was 17 328 (5 750 - 27 996) with a maximum sustainable yield of 317 (25 - 1 107). They conclude that current harvests are below MSY.
The aerial surveys of belugas spending the winter along the West Greenland coast have indicated a decline in numbers between 1981 and 1999. The estimate of abundance from 1998 and 1999 was 7941 (95% CI = 3 650 – 17 278) and does not differ significantly from the estimate of 11 563 (8 560 – 15 621) from 1993-1994. However, when the 1981-82 index of abundance (3302 SE=958) and the 1998-99 estimates (735, SE=025) are compared, the difference is significant (Heide-Jørgensen and Acquarone 2002, Innes and Stewart 2002).
Annual catches of belugas off West Greenland, corrected for under-reporting and sinking loss, including ice entrapment mortalities, for the period from 1979 to 1999, ranged from an estimated low of 650 to a high of 941 (Heide-Jørgensen and Rosing-Asvid 2002). Innes and Stewart (2002), using the largest estimates of abundance for the West Greenland group, calculated that the sustainable yield for 1999 would have been a total of 109 landed belugas. Their model suggested a decline of 50% in this wintering group during the period 1981 to 1994, compared with 62% based on all winter aerial surveys analysed by Heide-Jørgensen and Reeves (1996).
Inuit from three of four west Greenland communities believe that the numbers of belugas have slightly decreased or remained stable. One community notes a possible increase. Most hunters indicate that there is a noticeable variation in beluga numbers from year to year (Thomsen 1993).
Large commercial hunts in Cumberland sound from 1868 to 1939, particularly in Clearwater Fiord, the main centre of aggregation, reduced the original population of some 5000 whales (Mitchell and Reeves 1981) to less than 1000 individuals in the 1970s (Brodie et al. 1981). Aerial surveys carried out in Clearwater Fiord have provided an index of abundance for this population. Surveys flown in 1979 produced a maximum count of 550 belugas; and from 1979 to 1982, a maximum count of 541 belugas (Richard and Orr 1986). In August 1990, maximum counts in Clearwater Fiord ranged from 454 to 497, whÎle counts from two surveys in 1999 were in excess of 700 belugas. A significant number of belugas were also seen in 1999 in strip transect surveys of Cumberland Sound proper and offshore from Cumberland Sound (Richard and Baratin 2002).
The 1999 surveys estimated the numbers of belugas in the Cumberland Sound population, corrected for submerged animals, to be 1547 (95% CI=1187-1970; DFO 2002a). The lack of past comparable data makes it difficult to comment on the trends of abundance in this population.
The numbers of belugas entering Clearwater Fiord in Cumberland Sound is reported to have declined from the 1940s to the present. The Inuit of Pangnirtung believe that the major cause of the decrease was the large commercial harvests in the early part of the 20th century (Kilabuk 1998). There is a current quota of 41 belugas for this population, taken by the community of Pangnirtung.
Aerial surveys in 1992 provide an index of abundance of 19629 (95% C.L. = 15 131-24 125) (Harwood et al. 1996) for this population. This is uncorrected for submerged animals. It is also now known from VHF telemetry studies that some belugas in this population travel northwest into the ice-covered Viscount Melville Sound to feed in the summer (Richard et al. 2001b). The estimate of abundance is likely to have been an underestimation since it was based solely on surveys in the area of the Mackenzie Delta (DFO 2000). The US National Marine Fisheries Service (2002) tried to correct the Harwood (1996) estimate for diving animals, coming up with an estimate of 39 258 which was still considered conservative.
The Inuvialuit harvests for this population have been well documented since 1973. WhÎle the human population has increased in the area during this period, the number of whales harvested has slightly declined. The estimated total annual removal from this population, including struck and lost animals and Alaskan harvests, is 186 (Harwood et al. 2002). There might also be a few removals from Russian hunts when the animals occupy the winter areas, but this is thought to be very low. The continued harvest of large old individuals in the landed catch indicates that this harvest level has little impact on the population and that the present catch is well below the sustainable yield (DFO 2000).
The Inuvialuit have long depended on the beluga as a principal resource (McGhee 1974). The past 100 years have seen an evolution of hunting techniques from kayaks to whale boats to boats equipped with outboard motors (Day 2002). Even with the increasing human population in the Mackenzie Delta, the total annual catch of belugas has remained relatively constant during the past 20 years as has the age structure of the landed catch (DFO 2000, Harwood and Smith 2002). The Inuvialuit have not noticed any changes in abundance or distribution of belugas in their hunting areas.
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