Delphinapterus leucas (Pallas, 1776)

English: White whale; beluga
German: Weißwal; Beluga
Spanish: Beluga; ballena blanca
French: Belouga, dauphin blanc; marsouin blanc

Family Monodontidae

Delphinapterus leucas © Wurtz-Artescienza (see links).

1. Description

The common name of the beluga refers to its most striking feature and is derived from the Russian word "beloye" meaning "white". The white whale is a medium-sized odontocete, 3.5-5.5 m long and reaches a mass of up to 1,500 kg. Males are more robust and 25% longer than females (O'Corry Crowe, 2009). They lack a dorsal fin, which may be an adaptation to life in the ice also reducing heat loss. Instead, they possess a predominant dorsal ridge which is used to break through thin sea ice. Unlike most other cetaceans, they have unfused cervical vertebrae, allowing lateral flexibility of the head and neck. Young are about 1.6m long and are born a grey-cream colour, which then turns to dark brown or blue-grey. The distinctive pure white colour of beluga whales is reached in 7 year old females and 9 year old males (O'Corry Crowe, 2009). Maximum recorded age is 80 years (Stewart et al. 2006).

2. Distribution

Beluga whales are widely distributed around the Arctic Ocean and adjacent seas, and occur mainly in shallow shelf waters. Their range covers Hudson and James Bay; Somerset Island, Devon Island, the east coast of Baffin Island, and Ungava Bay; the northwest coast of Greenland from Inglefield Bredning south to Julianehab; the vicinity of Scoresby Sund on the East-central coast of Greenland; the Arctic coast of western and central Eurasia, from the Barents and White Seas east to the Laptev Sea, including Svalbard, Zemlya Frantsa Iosifa, Novaya Zemlya, Severnaya Zemlya, and Novosibirskiye Ostrova; the Arctic coast of eastern Siberia from Ostrov Vrangelya to Bering Strait; the Bering Sea south to Anadyrskiy Zaliv and Bristol Bay; the Arctic coast of Alaska and Northwestern Canada from the Chukchi Sea and Kotzebue Sound east to the Beaufort Sea. Vagrants were observed off New Jersey, Iceland, the Faroes, Ireland, Scotland, the Atlantic coast of France, the Netherlands, Denmark, Japan and Washington State (Rice, 1998).

Beluga distribution (Jefferson et al. 2008; © IUCN): the northernmost extent of its known distribution
is off Alaska and northwest Canada and off Ellesmere Island, West Greenland, and Svalbard (above 80°N). The southern limit is in the St. Lawrence river in eastern Canada (47°-49° N;
O'Corry-Crowe, 2009; © IUCN; click here for large map).

A number of independent stocks have been identified based on differences in body size between different distribution areas, non-uniform distribution pattern, return to predictable, specific coastal areas, differences in contaminant signatures, and geographic variation in vocal repertoire (O'Corry Crowe, 2009). Although dispersal among separate summering concentrations is limited (Brown Gladden et al. 1997; O'Corry Crowe et al. 1997), it is possible that many sub-populations overwinter in the same area, where interbreeding may occur (de March et al. 2002).

According to Rice (1998), there are five widely disjunct populations a) in the Saint Lawrence estuary, b) in the northern and c) western Sea of Okhotsk including Tatarskyi Zaliv, d) in Cook Inlet and e) in the Northern Gulf of Alaska.

In particular, beluga from western North America (Bering Sea) can be clearly distinguished from beluga from eastern North America (Hudson Strait, Baffin Bay, and St. Lawrence River). Based upon a combined data set (mitochondrial and nuclear DNA), Gladden et al. (1999) divided the population of North American beluga whales into two evolutionarily significant units.

3. Population size

The beluga population is subdivided into management units to reflect distinct groups of beluga at summering locations. In its 2000 report, the IWC recognises 29 putative stocks for:
1) Cook Inlet, 2) Bristol Bay, 3) E. Bering Sea, 4) E. Chukchi Sea, 5) Beaufort Sea, 6) North Water, 7) W. Greenland, 8) Cumberland Sound, 9) Frobisher Bay, 10) Ungava Bay, 11) Foxe Basin, 12) W. Hudson Bay, 13) S. Hudson Bay, 14) James Bay, 15) E. Hudson Bay, 16) St. Lawrence, 17) Svalbard, 18) Franz Josef Land, 19) Ob Gulf, 20) Yenesy Gulf, 21) Onezhsky Bay, 22) Mezhenskyi Bay, 23) Dvinskyi Bay, 24) Laptev Sea, 25) W. Chukchi - E. Siberian Seas, 26) Anadyr Gulf, 27) Shelikov Bay, 28) Sakhalin-Amur, and 29) Shantar. Stock boundaries sometimes overlap spatially and in such cases the geographical delineation of white whale stocks must have a temporal component (IWC, 2000).

Beluga at l'Oceanografic, Valencia, Spain 2008 @ Nicolai Culik

Alaska:
1. Cook Inlet: The most recent abundance estimate resulting from a 2007 aerial survey is 375 (CV = 0.21) animals (NMFS unpubl. data). While this estimate is larger than the estimates of 278 for 2005 and 302 for 2006, it is equivalent to the average of 370 for the years 1999-2004 (Angliss and Allen, 2008a). Whereas a review of the status of the population indicated that there is a 65% chance that the population will decline (Hobbs et al. 2006), a trend line fit to the estimates for 1999 to 2007 estimates an average rate of decline of 2.8% per year, which is not significantly different (CI = 95%) from a constant population level (Angliss and Allen, 2008a). Killer whale predation on belugas in Cook Inlet, Alaska, has become a concern since the decline of these belugas was documented during the 1990s. Shelden et al (2003) suggest a minimum estimate of roughly 1 death per year due to killer whale predation.

2. Bristol Bay: The maximum counts for 2004 and 2005 give corrected population estimates of 2,455 and 3,299 (L. Lowry, University of Alaska Fairbanks, pers. comm. to Angliss and Allen, 2008b). Data from 28 complete counts of Kvichak and Nushagak bays made in good or excellent survey conditions were analyzed, and results showed that the population had increased by 65% over the 12-year period between 1993 - 2005 (Lowry et al. in prep)

3. East Bering Sea: The population size estimated for Norton Sound from aereal surveys conducted in 2000 is 18,142 (CV = 0.24). Data currently available do not allow an evaluation of population trend for the Eastern Bering Sea stock (Angliss and Outlaw, 2005). The 2000 IWC abundance estimate was 12,675 .

4. Eastern Chuckchi Sea: The abundance estimate from the 1989-91 surveys (3,710 whales) is still considered to be the most reliable for the eastern Chukchi Sea beluga whale stock (Angliss and Allen, 2008c).

5. Beaufort Sea: The most recent aerial survey was conducted in 1992 and resulted in a corrected estimate of 39,258 (CV = 0.46) (Angliss and Allen, 2008d). The population was designed as Not at Risk by COSEWIC (2004).

Canada and West Greenland (IWC, 2000):
6. North Water (Baffin Bay): 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. 2002). The IWC (2000) estimate was 28,000 animals.

7. West Greenland: Surveys conducted in 1998 and 1999 found 7,941 (95% CI: 3650-17278) belugas in West Greenland (Heide-Jørgensen and Acquarone, 2002). The IWC (2000) estimate was only 2000 animals.

8. Cumberland Sound: This stock numbers about 1,500 animals and is thought to have increased since the 1980s (COSEWIC 2004): the IWC (2000) estimate was only 485 animals. The population was designed as Threatened by COSEWIC (2004).

9. Frobisher Bay: no data available

10. Ungava Bay: < 50 (Hammill et al.2005). These animals may be remnants of the former stock, or transient or recolonising animals. Ungava Bay was formerly a summering area for a group of beluga, but these appear to have been extirpated by over-harvesting. Only very small numbers of belugas are observed there now, and are sometimes harvested (Heide Jørgensen, 2005). The population was designed as Endangered by COSEWIC (2004).

11. Foxe Basin 1,000 (IWC, 2000). This stock is listed as "Endangered" by COSEWIC (2004).

12. West Hudson Bay 25,100 (IWC, 2000). There is no recent data available (Jefferson et al. 2008). The population was designed as Special Concern by COSEWIC (2004).

13. South Hudson Bay 1,299 (IWC, 2000).

14. James Bay 3,300 (IWC, 2000).

15. East Hudson Bay: Belugas in Eastern Hudson Bay have declined from 4,200 (SE 300) in 1985 to 3,100 (SE 800) in 2004 (corrected estimates) (Hammill et al. 2005). The population was designed as endangered by COSEWIC (2004).

16. St Lawrence River: Recent population estimates for 1998-2000, corrected for submerged animals and rounded to the nearest 100, range from 900 to 1300. 1,238 (COSEWIC, 2004). This compares positively with the estimate of Lesage and Kingsley (1998) of between 600 and 700 who found that the population was slowly increasing. Reproductive rates, survival rates at each age, and population age structure were similar to those of other beluga populations. The population was designed as Threatened by COSEWIC (2004).

Svalbard:
17. Svalbard: Belugas have never been surveyed around Svalbard (Jefferson et al. 2008). Pods numbering into the thousands are sighted irregularly around the archipelago, and pods ranging from a few to a few hundred individuals are seen regularly (Kovacs and Lydersen 2006). The IWC (2000) estimates population size at between few hundreds to low thousands.

Former Soviet Union (Bjoerge et al. 1991; IWC, 2000):
18-24 W. Siberia: 500-1,000 (Barents - Laptev Sea)
25 East Siberia: 2,000-3,000 (W Chukchi - E Siberian Sea)
26 Anadyr Delta: 200-3,000
27-29 Sea of Okhotsk: 18,000-20,000
The data for the former Soviet Union differ somewhat from the population estimates given in Reyes (1991). According to the IWC (2000) report, stocks 18 - 23 number in the low hundreds, whereas there is no information on stock 24. Another estimate made later guesses that from 15,000 to 20,000 beluga inhabited the White, Barents and Kara Seas (Boltunov and Belikov 2002).

4. Biology and Behaviour

Habitat. White whales seem to prefer shallow coastal waters and river mouths, although they may migrate through deep waters. In some areas they are reported to spend most of their time in offshore waters, where feeding and calving may take place (Reyes, 1991 and refs. therein). In Alaska's Cook Inlet, mudflats were a significant predictor of beluga distribution during early summer months (Goetz et al. 2007). In the north-eastern Chukchi Sea, the presence of near-shore gravel beds and warm, low-salinity water probably combine to make this region important as a place for belugas to moult (Frost et al. 1993). In the eastern Beaufort Sea, satellite-tagged beluga females with calves and smaller males select open- water habitats near the mainland; large males select closed sea ice cover in and near the Arctic Archipelago; and smaller males and two females with calves (not newborn) selected habitat near the ice edge (Loseto et al. 2006). The authors conclude that summer habitat segregation of belugas reflects differences in foraging ecology, risk of predation, and reproduction. Barber et al. (2001) found beluga distribution in the Canadian Arctic to be bimodal with respect to bathymetry, with a larger mode in shallow water and a smaller mode in water approximately 500 m deep. There is a general tendency for males in the eastern Arctic to be associated with shallow water during the summer and deeper water (modes at 100 and 500m) in the fall (Barber et al. 2001).

Food: Feeding habits vary, depending on geographical location and season. Belugas dive regularly to the sea floor at depths of 300-600 m. In the deep waters beyond the continental shelf, belugas may dive in excess of 1,000 m and may remain submerged for more than 25 min (Richard et al. 2001, Martin et al. 1998). In the Beaufort Sea, beluga feed predominantly on Arctic cod (Boreogadus saida) collected from near shore and offshore regions (Loseto et al. 2009). In western Hudson Bay they feed on capelin (Mallotus villosus), river fish such as cisco (Leucichthys artedi) and pike (Esox lucius), marine worms and squids. Further north, belugas rely on crustaceans, arctic char (Salvelinus alpinus), Greenland cod (Gadus ogac), and arctic cod. In the St.-Lawrence, capelin, American sand lance (Ammodytes americanus), marine worms and squid are eaten, while in Alaskan waters the species feed on fish, mainly salmon. Evidence for offshore feeding comes from finding offshore squid (Gonatus fabricii) in the stomach of whales in the Beaufort Sea (Reyes, 1991 and refs. therein).

Schooling: Beluga whales are highly gregarious. They are found in groups of up to about 15 individuals, but aggregations of several thousand can be observed at times. Pods are often segregated by age and sex (Jefferson et al. 1993).

Reproduction: Calves are born in spring to summer, between April and August, depending on the population (Jefferson et al. 1993).

5. Migration

General patterns:
Not all white whales are migratory. Some populations are resident in well-defined areas, for example in Cook Inlet, the St. Lawrence estuary and possibly in Cumberland Sound (Reyes, 1991). As determined by radio-telemetry, whales use waters e.g. in the upper Cook Inlet intensively between summer and late autumn and disperse to mid-inlet offshore waters during winter months (Hobbs et al. 2005). They remain in the inlet for the whole year (Rugh et al. 2004).

Other populations are strongly migratory and their migration shows a seasonal pattern. In the winter, they move to offshore waters, staying at the edge of the pack ice or in polynyas. Although these migrations occur regularly, routes and dates are poorly known (Reyes, 1991). The basic migratory schedule, however, is quite consistent and seems to be governed primarily by photoperiod rather than by other physical or biological factors, including sea-ice conditions (Heide-Jørgensen and Reeves, 1996).

Beluga at l'Oceanografic, Valencia, Spain 2008 @ Nicolai Culik

White whales that spent the winter in the central and south-western Bering sea along the Russian coast move north along the west coast of Alaska and the east coast of Russia from April through early summer. There are indications that populations from western Hudson Bay, eastern Hudson Bay and Ungava Bay overwinter together in the pack ice in Hudson Strait. In spring the whales from each population separate and migrate to their distinct summering grounds. Populations from the White, Kara and Laptev Seas overwinter in the Barents Sea (Reyes, 1991 and refs.therein).

Genetic studies of white whales suggest that there is limited movement between major summering grounds and therefore that colonisation of depleted areas by whales from other summer concentrations would be slow. Recent satellite tracking data show white whales to be less ice-limited than previously thought; they travel long distances into the permanent polar ice during the summer. Thus, ideas about the physical barriers to movement and hypotheses concerning the convergence of several summering stocks on a single wintering ground may need to be reconsidered (IWC, 2000).

In the spring, migrating whales from different stocks may approach and move past a given site in 'waves', while a summer 'resident' stock moves into that same area for an extended period. For example, the Eastern Chukchi Sea stock is temporally delineated as the group of whales that arrives in Kotzebue Sound or Kasegaluk Lagoon as the ice begins to break up and remains there for at least several weeks. Earlier in the year, whales from the Beaufort Sea stock move through this area in the spring lead system. Thus, the annual catch at villages such as Point Hope, Kivalina and Barrow can consist of whales from both of these stocks (IWC, 2000).

In summer, belugas ascend rivers: the Severnaya Dvina, Mezen', Pechora, Ob' Yenisey in Asia, the Yukon and Kuskokwim Rivers in Alaska and the St. Lawrence River in eastern Canada (Rice, 1998). A study by Aubin (1989) demonstrated that occupation of river estuaries is an important metabolic stimulus to belugas, and facilitates epidermal renewal in a manner analogous to a moult. There are a few records of solitary individuals ranging thousands of kilometres up various rivers (c.f. Gewalt, 1994).

Detailed accounts:
Several studies involving satellite-transmitters were conducted in recent years. The following accounts are sorted from east to west, beginning in the Bering and Chukchi Seas.

Richard et al. (2001b) satellite-tagged beluga whales of the eastern Beaufort Sea during summer and autumn between 1993 and 1997. Whales occupied the Mackenzie estuary intermittently and for only a few days at a time. They spent much of their time off-shore, near or beyond the shelf break and in the polar pack ice of the estuary, or in Amundsen Gulf, Mc'Clure Strait, and Viscount Melville Sound. Their movements into the polar pack ice and into passages of the Canadian Arctic Archipelago suggest that aerial surveys conducted in the southeastern Beaufort Sea and Amundsen Gulf may have substantially underestimated the size of the eastern Beaufort Sea stock. Conclusions from this study about beluga ecology challenge conventional wisdom, in that estuarine occupation appears to be short-lived, belugas travel long distances in summer to areas hundreds of kilometres from the Mackenzie Delta, and they do not avoid dense pack ice in summer and autumn (Richard et al. 2001a).

Suydam et al (2001) satellite-tracked five belugas in Kasegaluk Lagoon, eastern Chukchi Sea in summer. Two tags transmitted for only about two weeks, during which time one animal remained in the vicinity of Icy Cape, 80km north of the capture site, and the other travelled to Point Barrow, about 300 km north. The other three tags operated for 60-104 days, and those belugas travelled more than 2,000 km, reaching 80°N and 133°W, almost 1,100km north of the Alaska coast. This journey required them to move through 700km of more than 90% ice cover. Two of the whales then moved southward into the Beaufort Sea north and east of Point Barrow. Two whales later moved to an area north of the Mackenzie River delta, where they spent 2-3 weeks before once again heading southwest towards Barrow (Suydam et al. 2001).

Richard et al. (2001b) live-captured and instrumented 21 adult belugas (8M, 13F) with satellite-linked transmitters in the summer and fall of 1996 on the Canadian north-east coast: Twelve were captured in estuaries along the coast of Somerset Island in July and nine were captured in September in Croker Bay, SE Devon Island. Most of the animals moved rapidly to southern Peel Sound, where they all spent the month of August, making frequent deep dives, some of which were to depths near or at the seabed of the Franklin Trench. The belugas also used several bays along the coast of Prince of Wales Island and another one on Melville Peninsula. They left southern Peel Sound between late August and early September and moved rapidly to the south coast of Devon Island, many using Maxwell Bay and Croker Bay for several days. All belugas instrumented in Croker Bay in September, as well as the summer-tagged individuals that were still transmitting, moved east and north along the south and east coasts of Devon Island, eventually reaching Jones Sound and north Baffin Bay. They used many bays along the east coast of Devon Island and dove to depths often exceeding 200m in the surrounding waters. Fifteen of the tags continued to transmit during the period when belugas are normally observed migrating along the West Greenland coast (late September-early October). However, only one of the tagged animals moved to Greenland waters in late September. The others remained in the area known in winter as the North Water. The autumn tracking results suggest that the North Water may harbour a larger winter population of belugas than was previously suspected (Richard et al. 2001b).

Of five belugas tracked by satellite from Creswell Bay, Somerset Island, in the Canadian high Arctic in October (Heide-Jørgensen et al. 2003) three stayed in the North Water polynya and the other two whales moved to West Greenland. One of the whales that moved to Greenland migrated south along the west coast. Based on the total number of belugas satellite-tracked in Canada between 1995 and 2001 with tags that lasted beyond 1 October, approximately 15 % (95% CI 0.06-0.35; n=26) of the summering stock of belugas in the Canadian high Arctic move to West Greenland for the winter (Heide-Jørgensen et al. 2003).

In eastern Hudson Bay belugas tagged in summer made no directed or long-distance movements (Kingsley et al. 2001). All animals showed dive depth characteristics that were consistent with diving usually to the bottom. However, all belugas always- even in deep water-made dives that usually lasted less than 10 min and very seldom lasted more than 12-min. Belugas tagged as pairs of adults and young showed striking correlations of dive behaviour. According to Kingsley et al. (2001) the data obtained indicate that it would be appropriate to correct aerial surveys by adding 85% to aerial counts.

In Svalbard, satellite-tagged beluga spent most of their time relatively stationary, close to different glacier fronts in the area and foraging is the probable reason for this behaviour (Lydersen et al. 2001). When the whales changed location, they did so in an apparently directed and rapid manner. Average horizontal swimming speed was at least 6 km/h during long-distance movements. Movements between glacier fronts were extremely coastal in nature and took place in shallow waters. This behaviour has probably developed as a means of avoiding predators (Lydersen et al. 2001). K. Kovacs (U. Tromsø, pers. comm.) found that none of these tagged animals left Norwegian waters. If they are "linked" to any population it is likely with Russia.

As opposed to these high-tech approaches, traditional ecological knowledge (TEK) has been used opportunistically in biological studies of beluga whales in Alaska (Huntington, 1999) and Russia (Mymrin and Huntington, 1999). Their results are consistent with those of previous studies but add considerable detail, including descriptions of avoidance and habituation responses to anthropogenic noise, which appear to depend in part on association with hunting activities.

6. Threats

Direct catches: A permit for a catch quota of 1,000 beluga whales has been issued by the Russian Commission for Fisheries in 2002. The Small Cetacean Subcommittee of the IWC expressed concern over such takes of small cetaceans when there was insufficient information to adequately assess the impact, and recommended an assessment of the size of the affected populations and the impacts of the removals (W. Perrin, pers. comm., 2003).

The most immediate concerns relate to continuing harvests from small and depleted populations (IWC, 2000), e.g. in Eastern Hudson Bay and Ungava Bay in the Canadian Arctic (COSEWIC, 2004). A dramatic decline is recorded in West Greenland since 1981, but surveys to estimate the total abundance are either incomplete, have wide confidence limits or are too old to be used to adjust present catches to sustainable levels (Heide-Jørgensen, 1994). Alvarez-Flores and Heide Jørgensen (2004) find that current catches are still unsustainable and that continuation of this situation represents a 90% probability that the population will become extinct in 20 years. Their analyses suggest that the harvest should be reduced to no more than 130 animals, or about 25 % of current catches (606 in 2000 and 399 in 2002; Heide- Jørgensen, 2005).

Beluga have long been a vital food resource for Canadian Inuit. The top layer of skin, called muktuk, is a good source of Vitamin C and other nutrients. Management of beluga and other marine mammals in Canada are a federal responsibility. Canada discontinued all commercial whaling in 1972, and hunting of beluga today is allowed for subsistence purposes only (Heide- Jørgensen, 2005). Between 1988 and 1996, the total annual subsistence harvest of beluga varied between 400 and 700 (DFO 2002).

Whereas direct takes are mostly from aboriginal hunting, indirect takes are primarily from incidental catch in fishery operations.

Global warming: As recent decreases in ice coverage have been more extensive in the Siberian Arctic (60° E-180° E) than in the Beaufort Sea and western sectors, Tynan and De Master (1997) speculate that marine mammals in the Siberian Arctic may be among the first to experience climate-induced geographic shifts or altered reproductive capacity due to persistent changes in ice extent. Alteration in the extent and productivity of ice-edge systems may affect the density and distribution of important ice-associated prey of marine mammals, such as arctic cod (Boreogadus saida) and sympagic ("with ice") amphipods. The timing of the phytoplankton bloom, driven by the break up and melting of ice, is critical to the immediate success of first-feeding larvae of Arctic cod. Alteration in the extent, timing and productivity of ice-edge systems may therefore affect the density and distribution of Arctic cod, and in turn the foraging success and nutritional condition of dependent species such as beluga and narwhal (Tynan and DeMaster, 1997; Everett and Bolton, 1996; IWC, 1997).

Beluga distribution is divided into a number of non-contiguous areas in northern polar and sub-polar waters. In addition, there is a reliance on shallow coastal areas in summer months. As a result, their ability to move their range poleward as water temperatures increase and ice coverage decreases may be limited by the absence of suitable shelf and coastal waters further north in the Arctic Ocean. In addition, isolated populations at the southern edge of the current species range, such as in the Gulf of St. Lawrence, may be limited in their ability to shift their range northward and these populations may become extinct as a result of changes in water temperature (MacLeod, 2009).

Ambient noise: Movements of belugas through the mouth of the Saguenay river have been monitored by several researchers during the last decade. After selecting comparable data from each research group, Caron and Sergeant (1988) noted a decline in beluga passage rate of more than 60% over this period (from 3.9 belugas/hour to 1.3 belugas/hour in the later years). The decline occurred over a relatively short period, between 1982 and 1986, which coincided with an increase in recreational boat activities in the area. Without excluding other influencing factors inside or outside the Saguenay area, a link between boat traffic and beluga passage was hypothesized.

Cosens and Dueck (1993) found that the ice breaker MV Arctic generated more high frequency noise than did comparable vessels and that belugas should be able to detect the vessel from at least as far as 25 to 30 km. This may explain why belugas in Lancaster Sound seem to react to ships at longer distances than do other stocks of arctic whales. Typically, belugas moved rapidly along ice edges away from approaching ships and showed strong avoidance reactions to ships aproaching at distances of 35-50 km when noise levels ranged from 94-105 dB re 1 µPa in the 20-1000 Hz band. The "flee" response of the beluga involved large herds undertaking long dives close to or beneath the ice edge; pod integrity broke down and diving appeared asynchronous. Belugas were displaced along ice-edges by as much as 80 km (Finley et al. 1990). The magnitude of this avoidance reaction was attributed to the animals being mostly "naïve" to anthropogenic sound pollution.

Habitat degradation: Potential threats further include oil and gas development, over-harvesting, fisheries, hydroelectric development in Hudson Bay, industrial and urban pollution and climate change. Reyes (1991 and references therein) summarised that hydroelectric development is one of the most important effect of human activities on white whales, which rely on warmer waters in estuaries and rivers for calving and early growth of young. Areas such as the McKenzie Delta and others are subject to oil exploration, which implies seismic ship surveys, offshore drilling or artificial island construction. These activities are undertaken in the summer months in the same areas occupied by belugas at this time of year. Frost et al. (1993) suggest that activities associated with oil, gas, coal, and mineral resource development should be regulated to minimise their potential impacts on important beluga habitats.

Pollution: A small geographically isolated sub-Arctic population of belugas reside year-round in a short segment of the St. Lawrence river estuary. For more than 50 years the belugas have been exposed to industrial pollutants including organochlorines, polycyclic aromatic hydrocarbons (PAH), and heavy metals. Studies have found that concentrations of both total PCBs and highly chlorinated PCB congeners were much higher in St. Lawrence belugas than Arctic belugas. Scientists believe that the increased occurrence of opportunistic bacterial infections, parasitic infestation, gastric ulcers and other disorders in St. Lawrence beluga whales was evidence of a link between immune system dysfunction and PCB exposure (Martineau et al. 1994). Belugas feed significantly on bottom invertebrates, and have been observed partially covered by mud when surfacing, suggesting that they dig into contaminated sediments (Dalcourt et al. 1992). However, between 1987 and 2002 concentrations of most of the bioaccumulative and toxic chemicals (PBT) examined have exponentially decreased by at least a factor of two while no increasing trends were observed for any of the PBTs measured. This was attributed to a decline in contamination of beluga diet following North American and international regulations on the use and production of these compounds or by a change in its diet itself or by a combination of both (Lebeuf et al. 2007).

Beluga whales have been hunted for food by Native People in the Canadian Arctic since prehistoric time. While earlier analyses suggested that whales in the western Canadian Arctic had higher levels of mercury than those from the eastern Canadian Arctic, such regional differences have diminished and are no longer statistically significant. Nevertheless, mercury levels in muktuk still exceed the consumption guideline in most instances (Lockhart et al. 2005). But although mercury levels in the Beaufort Sea beluga population increased during the 1990s levels have since declined (Loseto et al. 2008).

However, further contaminants such as PCBs, OC pesticides, polybrominated diphenyl ether (PBDE) flame retardants, methylsulfonyl- and hydroxy -PCB metabolites, and PBDEs were determined in the liver of beluga whales the St. Lawrence Estuary and western Hudson Bay. The results suggest a complexity of contaminant exposure that may be impacting the health of Canadian beluga whale populations (McKinney et al. 2006).

In the northeast Atlantic, the concentrations of toxaphene congeners in white whales from Svalbard are at the high end of the range for concentrations of these compounds compared to other populations suggesting exposure to high levels (Andersen et al. 2006). And the concentrations and patterns of polychlorinated biphenyls (PCBs), chlorinated pesticides, and polybrominated diphenyl ethers (PBDEs) were among the highest levels ever measured in marine mammals from the same area (Wolkers et al. 2006).

7. Remarks

Range states (Jefferson et al. 2008):
Canada; Greenland; Russian Federation; Svalbard and Jan Mayen; United States of America.

D. leucas is listed in Appendix II of CMS. The species is listed in Appendix II of CITES. The IUCN species experts group classifies the beluga as "Near Threatened" (Jefferson et al. 2008). This is based on substantial uncertainty about numbers and trends for at least some parts of the range, and on the cessation of national and international, taxon-specific conservation programs which could result in the beluga's qualifying for threatened status within five years. Some subpopulations qualify for threatened status but only one of these - the Cook Inlet subpopulation - has been assessed thus far (as Critically Endangered) (Lowry et al. 2006).

The IWC (2000) expressed concerns about the conservation status of a number of stocks because of their:
(1) depleted status relative to historical abundance (Cook Inlet, West Greenland, Ungava Bay, Cumber-land Sound, East Hudson Bay, St Lawrence River);
(2) likely depleted status relative to historical abundance (Svalbard, Ob Gulf, Yenesy Gulf, Onezhsky Bay, Dvinsky Bay, Mezhensky Bay, Shelikov Bay, Shantar Bay, Sakhalin-Amur);
(3) current small population size or reduced range (Cook Inlet, Ungava Bay, Cumberland Sound, West Greenland, Ob Gulf, Yenesy Gulf);
(4) recent decline (Cook Inlet, West. Greenland).

8. Sources

· Alvarez-Flores CM, Heide-Joergensen MP (2004) A risk assessment of the sustainability of the harvest of beluga (Delphinapterus leucas (Pallas 1776)) in West Greenland. ICES J. Mar. Sci. 61: 274-286.
· Andersen G, Foereid S, Skaare JU, Jenssen BM, Lydersen C, Kovacs KM (2006) Levels of toxaphene congeners in white whales (Delphinapterus leucas) from Svalbard, Norway. Sci. Total Environ. 357 : 128-137.
· Angliss RP, Allen BM (2008a): Beluga whale: Cook Inlet stock. Alaska Marine Mammal Stock Assessments, 2008 NOAA-TM-AFSC-193
· Angliss RP, Allen BM (2008b): Beluga whale: Bristol Bay stock. Alaska Marine Mammal Stock Assessments, 2008 NOAA-TM-AFSC-193
· Angliss RP, Allen BM (2008c): Beluga whale: Beaufort Sea Stock. Alaska Marine Mammal Stock Assessments, 2008 NOAA-TM-AFSC-193
· Angliss RP, Allen BM (2008c): Beluga whale: Eastern Chukchi Sea Stock. Alaska Marine Mammal Stock Assessments, 2008 NOAA-TM-AFSC-193
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© Boris Culik (2010) Odontocetes. The toothed whales: "Delphinapterus leucas". UNEP/CMS Secretariat, Bonn, Germany. http://www.cms.int/reports/small_cetaceans/index.htm
© Illustrations by Maurizio Würtz, Artescienza.
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