Mortalities disturbing of the St. Lawrence beluga

Mortalités inquiétantes de bélugas du Saint-Laurent

Photo: Lyne Morissette
This female known since 1990 was found dead. She would have died trying to give birth.

The St. Lawrence beluga whales continue to die at an alarming rate, especially as the females are always numerous in the annual reports of mortalities for this cetacean resident of the quebec waters. A total of 17 carcasses were found in 2019, some of which were of females died giving birth.

“The deaths recorded in the year 2019 did nothing to reassure us “, summed up Friday, the scientific director of Group for research and education on marine mammals, Robert Michaud, revealing the death toll from beluga last year.

In total, 17 animals that were found dead on the shores of the St. Lawrence river, in 2019, of which 10 are adults. The annual balance sheet is therefore situated in the average of the years 2018 (12 carcasses), 2017 (22 carcasses) and 2016 (14 carcasses).

However, scientists are concerned about the “high proportion” of females among deaths recorded. “Five of the six beluga adults examined at the Faculty of veterinary medicine for post-mortem examinations, were females, which suggests again this year that among adults, females have a mortality rate higher than that of males (assuming that the sample is representative of the total mortalities),” noted Stéphane Lair, a professor at the Faculty of veterinary medicine of the University of Montreal.

What’s more, half of the carcasses of females found in 2019 died of dystocia, therefore, at the time of giving birth. Three females exhibited a fetus that is visible at the level of the genital slit. Necropsies carried out by the team led by Dr. Stéphane Lair have helped to know that they are failed to as a result of complications during calving.

“This case unusually high dystocia, which is documented for a decade now in this population, is disturbing, and no doubt represents a threat to its conservation. The potential causes of this dystocia remain uncertain, ” explained Stéphane Lair. Work to better understand the potential link between these dystocia and contamination, some contaminants such as flame retardants polybrominated biphenyls are underway.

One thing is certain, ” the result of this black series does not bode well for the recovery of the beluga population of the St. Lawrence river “, according to Robert Michaud. The last population survey reported that approximately 880 belugas, so that they were more than 10 000 at the beginning of the 20th century. What’s more, the resident population of St. Lawrence decreased by an average of 1 % per year.

What are the causes ?

Several factors could explain these high mortality, which may thwart any recovery of the species, from the admission even of researchers studying beluga whales for several years.

The inconvenience suffered by whales in their summer habitat could weigh heavily in the balance. It is important to know that the places frequented by beluga whales, including females and their young, are subject to intense maritime traffic. One can think of commercial navigation, but also to boaters, many more to come in the summer time.

The risks posed by disturbance and noise pollution beluga habitat could increase in the coming years, due to the growth of maritime traffic, trade on the St. Lawrence river. The ports in Montreal and Quebec city are developing currently expansion projects. There are also on the Saguenay, including the LNG project in Quebec.

A project funded by the government of Quebec is also in the running until 2023, in collaboration with the University of Quebec in Outaouais, in order to determine the vulnerability of the species to the noise pollution. Last year, the government of Quebec and that of Canada had also agreed to enhance the protection of the summer habitat of beluga whales, by increasing the protected areas in the estuary of the St. Lawrence river. No official announcement has been made since that time.

Other threats

In addition to the threat of this disturbance continuing of the animals, the retreat of the ice in the gulf could also be adversely affected pregnant during the months prior to the birth of their calves. A phenomenon that could well take more and more importance due to the climatic upheavals that are affecting the St. Lawrence.

The researchers also highlight the need to better understand the impacts of a decline in stocks of herring, a prey to beluga whales, but also the accumulation of some contaminants in animals.

The flame retardants used in many products and objects, and are recognized as endocrine disruptors, could also have a negative impact on females in gestation or at the time of delivery.

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