As the years go by, the concern of St. Lawrence beluga specialists remains strong. According to a report received Duty. This mortality, which threatens the recovery of the species, highlights recurring problems during calving in an ecosystem increasingly disturbed by human activities.
“Unfortunately, this year we still have a high neonatal mortality rate. This is a trend that has been observed over the past decade and continues,” summarizes Robert Michaud, Scientific Director of the Marine Mammal Research and Education Group (GREMM) and Coordinator of the Quebec Marine Mammal Emergency Response Network (RQUMM).
Between March and December 2021, 19 carcasses of beluga whales were found on the banks of the Saint Lawrence River, including 11 in the Baix Saint Laurent. For comparison: in 2020 there were 14, in 2019 – 17, in 2018 – 22, in 2017 – 22 and in 2016 – 14. Thus, since 2016, deaths in this population barely 880 people.
“In 2021, the number of carcasses washed ashore exceeds the 39-year average of 14 carcasses,” says Stéphane Lair, professor in the Department of Veterinary Medicine at the University of Montreal. It is his team that performs autopsies on beluga whales (8 in 2021), which can be delivered to the faculty 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 washed ashore is higher” than the 1983-2007 average of one calf a year, Lair says. . However, this number of six dead very young beluga whales found does not exceed the annual averages calculated since 2008. This means that “excessive calf mortality is a phenomenon that has been observed for about a decade.”
In addition to the problems of replenishment of the population, researchers are concerned about female mortality. Last year, two females found dead had cases of dystocia, that is, death that occurred during childbirth. Moreover, a report prepared by Stefan Lair’s group has already concluded that difficult calving has become “the most important cause of adult female beluga whale mortality in the St. Lawrence River.”
While the number of white whales stranded ashore is a growing concern for scientists, as population declines continue, causes of death remain difficult to determine, says Robert Michaud.
“There are several hypotheses to explain this excess mortality. For example, it is possible that the physical condition of female beluga whales does not allow them to have the energy capacity for childbearing; in this case, excess neonatal mortality will be associated with a decrease in available food resources,” he explains.
GREMM’s scientific director, who has been studying the species for almost 40 years, adds that “the neurotoxic effects of certain chemical pollutants” can also affect “the health of both the mother and the newborn.” For several years, researchers have suspected that certain products are used as flame retardants in various items (textiles, computers, paint, etc.), but which are also endocrine disruptors that can harm birth.
It is possible that the physical condition of the female belugas does not allow them to have the energy to give birth; in this case, excess neonatal mortality will be associated with a decrease in available food resources.
Canadian fisheries and oceans researcher and cetacean specialist Véronique Lesage has already pointed out that certain chemicals can harm the species. Added to this are several factors that could threaten beluga whales: global warming, degradation of their habitat, reduced availability of prey, and the “chronic impact” of unrest caused by merchant ships, pleasure boats and kayaks.
What’s more, the Société des traversiers du Québec plans to carry out dredging and sediment removal operations year after year directly in the critical habitat of the St. Lawrence beluga whale. They will be held near Kakuna, an area considered to be a breeding ground for this species. The State Corporation will also conduct operations at times of the year when females are present in the sector accompanied by their cubs. But she assures that all measures will be taken to reduce the impact on this endangered population.