Necropsies on seven North Atlantic right whales found dead in the Gulf of St. Lawrence this summer show that four died of blunt force trauma from collisions with ships, while two appeared to die after being entangled in fishing gear. The cause of death for one whale was inconclusive.
Pierre-Yves Daoust, a pathologist and professor at the Atlantic Veterinary College (AVC), and Émilie L. Couture, a veterinarian with the Zoo de Granby and the Université de Montréal, made their findings public at the Atlantic Veterinary College this morning. Both are part of the Canadian Wildlife Health Cooperative.
The team released a report today outlining what killed six of the whales. The findings in the death of the seventh whale are not yet complete, but team says there are signs that the whale was entangled.
Daoust said it was very challenging to determine exactly how the whales died because they decompose so quickly.
Even determining that the whales were killed by blunt force trauma caused by ships was difficult, he said. The thick blubber and muscle on a right whale makes it hard to detect the injuries; only by examining damage to the whales' organs was the team able to conclude that a blunt force was responsible.
"But because of the major impact there can be shearing of some of the internal organs like liver, like heart, major blood vessels which cause sever internal hemorrhaging, severe internal bleeding which is what we think we saw," said Daoust.
It's likely most of these whales died in different areas and weren't part of the same pod.
Out of the seven whales that were examined, five were males and two were females. The entire right whale population is estimated to only consist of about 500 members, so any early deaths have a big impact on the species.
"The fact remains that human activities are a very important cause of this mortality this summer," said Daoust.
A total of 15 endangered right whales have been found dead off the East Coast of Canada and the U.S. this year. Twelve were found in Canadian waters, while three were off the U.S. coast. The whales ranged in age from two to 37 years old.
"This makes this pretty much the deadliest year we've seen since the days of whaling," said Tonya Wimmer director of the Marine Animal Response Society.
All those deaths led Transport Canada to introduce a mandatory 10-knot speed limit for large vessels in the Gulf to try and cut down on the number of deaths. Transport Canada now says it will look at removing that slow-down zone once the right whales begin to migrate south.
However, if the whales are spotted in other areas, the 10-knot speed limit will then go into effect there. There is no indication that the whales have started their migration yet.
Daoust said it is impossible to tell through a necropsy what kind of vessel killed a whale or how fast the ship was moving when the marine mammal was struck.
It's not clear what course of action should be taken to further protect the right whale.
Wimmer said everyone needs to come together to save the species. She believes an international working group should be formed to tackle the problem. Such a group would include members from the Canadian government, the U.S. government, scientists and the fishing industry.
"We're shifting focus towards what we can do as next steps, how we can go about preventing future mortalities going forward and those discussions are going to be taking place over the coming months," said Matthew Hardy a division manager with the Department of Fisheries and Oceans Canada.