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More than half the 70 North Atlantic right whale deaths recorded over the last 16 years were caused by entanglement in fishing gear or vessel collisions, a new study reports.

The paper published Thursday in the journal Diseases of Aquatic Organisms said a cause of death was determined for 43 of the 70 whales.

Of the 43, it was determined that 38 died as the result of human-induced trauma — either from vessel strikes or entanglement in fishing gear. The other five, all calves, died of natural causes.

"Of all the causes identified, it is critical to emphasize that no adult or juvenile North Atlantic right whale deaths were a result of natural causes. Not one," Sarah Sharp, a veterinarian with the International Fund for Animal Welfare and lead author of the study, said in a statement. "This is clear evidence that these animals are unable to live full, productive lives because they are dying prematurely as the result of human activities."

There are estimated to be only 411 North Atlantic right whales left, with deaths outpacing live births, and Sharp said the high rate of death is not sustainable for the population.

Another death was reported late Thursday.

In a release, Fisheries and Oceans Canada said a dead right whale was spotted northeast of the Magdalen Islands in the Gulf of St. Lawrence.

"Fishery officers have located the whale and installed a satellite tag to track it. We are currently assessing the recovery and necropsy options," the department said in the release.

A nine-year-old male right whale was found dead off the coast of New Brunswick this month, but preliminary necropsy results were inconclusive.

No right whales died in Canadian waters last year, but 12 were found dead in the Gulf of St. Lawrence in 2017, and another five died in U.S. waters that year.

Tonya Wimmer, a Canadian investigator with the Marine Animal Response Society in Nova Scotia, said the news from the study is bad.

"I think the one thing that is striking is that it is only a 16-year time period, and there were 70 North Atlantic right whale mortalities," she said in an interview Thursday.

Wimmer said compared with data from a previous study looking at the 1970s, the number of vessel strikes has actually increased in recent years.

Sharp said more aggressive efforts to protect the whales are needed, and the study makes a number of recommendations:

— Using newer fishing gear technology to minimize the chance of right whales encountering fishing line in the ocean.

— Expanding restrictions on vessel speeds to include larger areas of the whale habitat.

— Imposing fishery zone closures and mandatory speed restrictions when right whales are seen in certain areas.

— Supporting efforts to locate North Atlantic right whale carcasses so that accurate mortality statistics and necropsies can be done.

Wimmer said that while Canadian and American governments have responded with mitigation efforts, whales are still dying. "That is a very scary spot to be at. It means we have to try harder if we want to save them," she said.

Sharp said many of those efforts need to come from governments. She cited a Save the Right Whales Act now before the U.S. Congress and urged Canada's Department of Fisheries and Oceans to maintain mitigation efforts imposed after 2017.

"Not only are human activities killing whales at an unsustainable rate, but we also know from other studies that they also have a very low reproductive rate, meaning they are not giving birth to as many calves as they should as a population," Sharp said in an interview from Yarmouth Port, Mass.

She said those factors combine to paint a very negative picture about what could potentially happen to the species in the coming years.