The years go by, and the concern remains strong for the experts on the St. Lawrence beluga. No less than 19 individuals from this threatened population were found dead on the shores of the St. Lawrence in 2021, including six newborns, according to a report obtained by The duty. These mortalities, which compromise the possibilities of recovery of the species, highlight recurring problems at the time of calving in an ecosystem increasingly disturbed by human activity.
“Unfortunately, we still have a lot of neonatal mortality this year. This is a trend observed over the last decade and which is continuing,” summarizes Robert Michaud, scientific director of the Group for Research and Education on Marine Mammals (GREMM) and coordinator of the Quebec Marine Mammal Emergency Response Network (RQUMM ).
Between March and December 2021, 19 beluga whale carcasses were found stranded and sampled on the shores of the St. Lawrence, including 11 in the Bas-Saint-Laurent. By way of comparison, there were 14 in 2020, 17 in 2019, 12 in 2018, 22 in 2017 and 14 in 2016. The total since 2016 is therefore close to 100 belugas found dead, a count which does not, however, represent all deaths within this population of barely 880 individuals.
“In 2021, the number of carcasses found stranded is higher than the median of the last 39 years, which is 14 carcasses,” says Stéphane Lair, full professor at the Faculty of Veterinary Medicine at the University of Montreal. It is his team that performs beluga necropsies (8 in 2021) which can be transported to the Faculty’s laboratory, located in Saint-Hyacinthe.
Among the individuals found dead last year, ten were adults and six were very young belugas born in 2021. “The number of calves of the year found stranded is higher” than the median for the years 1983 to 2007 one calf a year, says Lair. However, this number of six very young belugas found dead falls within the annual average calculated since 2008. This means that “the excess mortality of calves has been a phenomenon that has been present for about ten years already”.
In addition to recruitment problems for the population, researchers are concerned about female mortalities. Last year, two females found dead were cases of dystocia, that is to say a death that occurred at the time of birth. Moreover, a report produced by Stéphane Lair’s team has already concluded that difficult calving has become “the most important cause of mortality for adult female belugas in the St. Lawrence”.
Explain mortalities
Although the number of belugas found stranded is of increasing concern to scientists, in a context where the population decline continues, the causes of death remain difficult to identify, specifies Robert Michaud.
“There are several hypotheses to explain these excess mortality. It is for example possible that the physical condition of female belugas does not allow them to have the energy capacity to give birth; in this case, excess neonatal mortality would be linked to a decrease in available food resources,” he explains.
The scientific director of GREMM, who has been studying the species for nearly 40 years, adds that “neurotoxic effects of certain chemical contaminants” could also affect “the health of both mother and newborn”. For several years, researchers have suspected in particular products used as flame retardants in various objects (textiles, computers, paint, etc.), but which are also endocrine disruptors which would harm births.
It is possible that the physical condition of female belugas does not allow them to have the energy capacity to give birth; in this case, excess neonatal mortality would be linked to a decrease in available food resources
Researcher at Fisheries and Oceans Canada and specialist in cetaceans, Véronique Lesage has already pointed out that certain chemical compounds could harm the species. Added to this are several factors likely to threaten belugas: global warming, the degradation of their habitat, a decrease in the availability of prey and “chronic exposure” to the disturbances caused by merchant ships, pleasure boats and kayaks.
What’s more, the Société des traversiers du Québec plans to carry out, year after year, dredging and sediment disposal work directly in the critical habitat of the St. Lawrence beluga. These will be carried out not far from Cacouna, an area considered a nursery for the species. The government corporation will also carry out the operations at a time of year when females accompanied by their young are present in the sector. But she assures that all measures will be taken to reduce the impacts on this endangered population.