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Species information

2. Basic Information on the Beluga Whale

2.1 Population

2.1.1 Significance of the population

Belugas living in the St.Lawrence estuary are considered a relict population distinct from other populations of the Arctic.  Recognition of the discreteness of this small population of belugas, mainly centred near the mouth of the Saguenay River, relied on the absence of any significant numbers of belugas in the areas contiguous to their location. Few belugas are found along the North Shore of the Gulf of St.Lawrence or the south Labrador coast confirming the lack of an extant connection between the belugas of the St.Lawrence and those populations occupying the sub-Arctic coastline of Quebec and Nunavut.

The St.Lawrence belugas are more genetically distinct than all other Canadian beluga populations. This population has one haplotype which has not yet been found anywhere else and another haplotype which is common only in belugas of eastern Hudson Bay, particularly those sampled in the Nastapoka River Estuary.  It has been postulated that both the St.Lawrence and Eastern Hudson Bay beluga might have originated from the inland sea of

the Lakes Agassiz and Ojibway, a refugium extant during the Wisconsin period of glaciation.

2.1.2 Distribution

This population is centred on the region influenced by the outflow of the Saguenay River. The summer distribution is well known and has changed little in the last twenty years. Recent aerial surveys have enumerated belugas in the whole of their summer range. No significant numbers are reported downstream past Ile du Bic or upstream past Ile aux Coudes.

Little is known of the winter distribution of St Lawrence belugas. There appears to be a slight increase in the use of the areas a little further downstream during the winter months

St Lawrence Riverbelugas now occupy only a small part of their former range, which extended further downstream to Pointe-des-Monts and Cap-Chat and upstream well past Ile aux Coudes. The belugas living near the Manicouagan River have been heavily exploited and the hydro-electric damming of the river might have resulted in their disappearance.

2.1.3 Population size and trend

Surveys of this population have been conducted since 1973. The analysis of the most recent photographic aerial survey made in 2000 has indicated no significant increase in numbers of belugas since 1988 when survey methodology was standardized.  Although the series of surveys made since 1973 suggest from the resulting abundance indices an apparent increase in population size, that conclusion is debated by scientists.  A precautionary conclusion is to consider the population stable until demonstrated otherwise.

Scientists measured experimentally a correction factor for submerged belugas invisible to aerial photography in the St.Lawrence.  Such a correction factor provides a mean to transform a survey index into an objective value of total population size.  The factor measured experimentally in the St.Lawrence was +109% which is comparable to factors developed for surveys made on belugas in the Arctic. Recent estimates of total numbers of belugas in the St.Lawrence population, corrected for submerged animals, are 1 209 individuals for the 1997 survey and 952 animals in 2000.  Part of the difference between these estimates can be attributed to the intrinsic error due to the photographic sampling methodology.

Standardization of survey methods since 1988 and periodic monitoring of this population in the future will probably result in deriving good estimates of the population trends.

2.2 Biology

2.2.1 Morphology

Beluga, Delphinapterus leucas, is a marine mammal.  This small toothed whale is characterized by a lack of dorsal fin, a melon-like structure on its head above the beak and its completely white color at maturity.  Males reach a total length of 2.6 m to 4.5 m and females a smaller size at approximately 80 % of that of the male, for a maximum of 3.5 m.  Animals of both sexes are similar in appearance. Newborn calves are pale grey at birth, sometimes with a darker mottled coloration, and 150 cm in length, which is half the length of their mothers.  Yearling calves are darker grey and 60-65% of their mothers’ length, at approximately 2 m.  Older juveniles gradually become paler in colour until they turn pure white at, or shortly after, the age of sexual maturity.

2.2.2 Reproduction

Beluga females mature sexually between 4 and 7 years old, males somewhat older, at 6 or 7 years.  Mating probably occurs at the end of winter or in the spring, in the wintering areas.  Gestation is estimated to be in the order 12.8 to approximately 14.5 months. The peak calving time appears to occur during the late spring migration or early summer but is not easily observed.  Lactation is estimated to last from 20 to 32 months.  It is estimated that a complete cycle between successive pregnancies is approximately 3 years.

2.2.3 Demography

Belugas are long-lived mammals with life spans in the range of 15-30 years.  Most population parameters available for belugas have been derived from samples of dead animals. The age specific frequencies obtained from collected belugas are subject to various sampling biases that make the accurate calculation of the survivorship of the age classes virtually impossible. An estimate of the instantaneous rate of increase of the population is consequently difficult to obtain from these demographic data. Nevertheless, it is felt that unexploited beluga populations, which are below carrying capacity, could increase at a rate in the range of 2.5 to 3.5 percent per annum.

2.2.4 Behavior

Belugas tend to form groups that can be discriminated by their sex composition or by the presence of juveniles. Distribution patterns within the territory occupied by the population likely reflect the ecological and behavioural needs of the different social groups. In fact, belugas exhibit a strong tenacity to specific sites.  Appproximately 20 such sites have been identified in the St.Lawrence estuary and in the Saguenay. Attachment to specific sites seems to be related to matrilinearity (social structure centered on a mother) and protection of those sites is thus crucial.  Two of the best known such sites are the passage of Ile-aux-Lièvres and Bay Sainte-Marguerite in the Saguenay.

2.2.5 Feeding and Diet

Feeding ecology of the St.Lawrence Beluga is not sufficiently known to determine whether its needs are faced with any problem.  Its diet is diversified and includes several species of fish and invertebrates.  Herring, capelin, tomcod, squid and polychete worms are among the species identified.  During the long winter season, its feeding strategies and availability of preys are unknown.  The trophic level occupied by belugas in the St.Lawrence is close but not identical to that of local species of seals.   Question is open about the possibility that other marine mammals could be competing with belugas for some food resources.

2.3 Why has COSEWIC given the Beluga Whale a threatened species status?

 

COSEWIC Assessment summary for the Beluga Whale (St.Lawrence population) - May 2004

  Common name

Beluga Whale (St.Lawrence population)

Scientific name

Delphinapterus leucas

Status

Threatened

Reason for designation

  That population was greatly reduced by hunting, which lasted until 1979. Heavy contamination may have also contributed to the decline of the population.  Aerial surveys since 1973 suggest that the decline in the population size has stopped, but do not provide clear evidence of an important increase in numbers.  Levels of many toxics are still high in the tissues of belugas.  The whales and their habitat are threatened by contaminants, maritime traffic and industrialization of the St.Lawrence River watershed.

Occurrence

  Quebec ; Atlantic Ocean

Status history

  Was designated “endangered” in April 1983 and April 1997.   Review of the status: the species was designated”threatened” in May 2004.  The last assessment was based on an updated report on the situation.

According to recent aerial surveys, the beluga population in the St.Lawrence estuary is considered stable or at least, is not dropping nor increasing at a measurable rate. Its size is approximately a thousand animals, of which 600 would be mature and able to contribute to reproduction. This is clearly higher than the numbers used when COSEWIC initiallly classified that population as endangered.  It was presumed then to include 350 individuals and be declining. When its situation was reviewed in 2004, the total number of individuals capable of contributing to reproduction was estimated at less than 1000, which prompted COSEWIC to recommend that it be considered threatened. The complete assessment report used for the revision of the status is available on the internet site of the SARA public registry.

2.4 What are the threats to the St.Lawrence Beluga Whale?

While belugas are subjected to various causes of natural mortality, such as predation and infectious disease, it is essentially human factors that should be identified and properly managed in order to promote the recovery of the St.Lawrence population of Beluga Whale.

The loss and perturbation of habitat is a continuing threat for St Lawrence belugas which live in a relatively restricted zone of a heavily traveled and populated area.  Both commercial shipping and whale watching activities have increased significantly in the area over the last 40 years. It has been demonstrated that boat traffic had a significant effect on the vocal behaviour of belugas.  Little is known of the immediate or chronic stress responses, which belugas might have to these various disturbances factors, and how it might affect their feeding, mating and nurturing behaviour.

Large numbers of beluga carcasses have been recovered along the inhabited shorelines of the St Lawrence River and have allowed considerable research into the causes of mortality. Links have been postulated between the prevalence of cancerous tumors and the exposure of St Lawrence belugas to industrial pollutants. Various contaminants known for their toxic and carcinogenous properties have been detected and often measured in high levels. But debates continue on whether correlations between pollutants and pathologies are truly indicative of a direct cause and effect relationship, and whether the sample of recovered carcasses is representative of measured cancer rates within the live population.  Because little information exists from other Arctic beluga populations on cancer rates and since the St Lawrence beluga cancer samples come mainly from old animals, it is difficult to evaluate this question.  There is nevertheless no doubt that belugas of the St.Lawrence are more exposed to pollutants than any other beluga population in Canada.

The small size and lower genetic diversity of this population has lead to the speculation that inbreeding might be suppressing the reproductive rates.  While the genetic diversity of this population is the lowest in all Canadian populations, the degree to which inbreeding suppression is a limiting factor is hard to evaluate. It should be noted that marine mammals, particularly seal populations of many species, have experienced severe reduction to very low numbers where a genetic bottleneck could have occurred and yet have rebounded to very high densities. Other genetic factors, such as changes at particular loci, might be implicated in a reduced capacity of the St Lawrence Population to respond to certain pathogens.

Other possible limiting factors include competition for resources with commercial fisheries and other increasing populations of marine mammals such as harp seals and grey seals. More detailed research must be conducted before the effect of competition can be critically evaluated, particularly since belugas eat a variety of food species, and are capable of deep foraging dives.  It should be noted however, that even with the high carcass recovery rate, no cases of starvation have been documented.