Two of six endangered North Atlantic right whales found dead during June in the Gulf of St. Lawrence showed signs of blunt trauma, suggesting they were victims of ship strikes, a wildlife pathologist leading the investigation told Canadian news media.

Necropsies on three whales June 30 and July 1 indicated the third had been entangled in fishing gear, said Dr. Pierre-Yves Daoust of the Atlantic Veterinary College in Charlottetown, Prince Edward Island, according to CBC News.

Daoust said the Canadian coast guard and industry need to look at preventing its “negative interactions” with right whales along the Atlantic coast of Canada and the U.S. With their total population estimated at a mere 525 animals, right whales are considered one of the most endangered species in the world.

“I would welcome the start of a discussion about this kind of potential interaction between an endangered species like the right whale, and the fishing industry and the shipping industry,” Daoust said. A seventh dead whale was reported July 6 by the Halifax-based Marine Animal Response Society, a regional marine mammal conservation group, which described the losses as devastating.

The discoveries raised widespread alarm among wildlife advocates and marine scientists, and could bring a new push for additional safeguards. In U.S. waters, the National Oceanic and Atmospheric Administration closely tracks right whale migration and feeding patterns, issues warning to the maritime industry to slow ship speeds in those areas, and requires commercial fishermen to use breakaway links in gill nets and lobster gear to reduce whale entanglements.

The deaths come a year after researchers described an apparent rebound of right whale numbers in the Bay of Fundy. Now this may be the single biggest mortality event among right whales since they were hunted by whalers in the 19th century, Mark Baumgartner, an associate scientist at the Woods Hole Oceanographic Institute in Massachusetts, told the Associated Press.

Volunteer teams have been rescuing other whales spotted in gear tangles. That work took a tragic turn July 10 when Joe Howlett, a Canadian commercial fisherman and volunteer with the Campobello Whale Rescue team, was struck and killed by a right whale off New Brunswick. Howlett, 59, had done the work for 15 years, and had freed another right whale just a few days before the accident.

Right whales were so named by those whalers for being the best species to pursue; they swim slowly, could be more easily harpooned on the surface, and float after death. Biologist say the population today is but a relic of what it was before widespread industrial-scale whaling, and the animals face other threats in the crowded East Coast sea lanes.

Experts have not ruled out other causes for the deaths, such as toxic algae blooms or other environmental condition, and tissue samples from the dead animals are being tested.

Contributing Editor Kirk Moore was a reporter for the Asbury Park Press for over 30 years before joining WorkBoat in 2015. He wrote several award-winning stories on marine, environmental, coastal and military issues that helped drive federal and state government policy changes. He has also been an editor for WorkBoat’s sister publication, National Fisherman, for over 25 years. Moore was awarded the Online News Association 2011 Knight Award for Public Service for the “Barnegat Bay Under Stress,” 2010 series that led to the New Jersey state government’s restoration plan. He lives in West Creek, N.J.