By TODD McLEISH/ecoRI News contributor
The deaths of six North Atlantic right whales in the Gulf of St. Lawrence last month have raised alarms among whale biologists who fear for the future of one of the rarest whales on the planet.
Robert Kenney, a marine mammal expert at the University of Rhode Island’s Graduate School of Oceanography, called the unexpected deaths “a major concern” because the population of right whales totals fewer than 500 animals and their numbers have been declining since 2011. The dead whales represent more than 1 percent of the population.
While the deaths raise many questions, one of the first, according to Kenney, is what were they doing in the Gulf of St. Lawrence in the first place?
“Right whales go to the same places to feed every year — the Great South Channel, the Bay of Fundy, the Nova Scotia shelf — feeding grounds they probably learned from their mothers in their first year of life,” said Kenney, who manages the sighting database for the North Atlantic Right Whale Consortium. “But recently they seem to be wandering farther afield. If there’s not enough food where they traditionally feed, they go to other places. That’s what we think is going on.”
What caused the deaths of the six whales in the Gulf of St. Lawrence — the water body surrounded by Newfoundland, Quebec, Nova Scotia and New Brunswick — is uncertain. Preliminary results of necropsies on three of the animals showed evidence of blunt trauma from ship strikes on two of the whales and fishing gear entanglement on the third. But a news release from Canada’s Marine Animal Response Society said other problems that “may have predisposed these animals to this trauma cannot be ruled out at this stage.”
Kenney is suspicious that a toxic algae bloom or some sort of disease may have been a factor. In 1987, a dozen humpback whales died from eating mackerel laced with a red tide toxin, he said.
Right whales were nearly driven to extinction because of commercial whaling. They were slow to recover, though their population increased steadily at about 3 percent annually from the 1980s through 2010, with what Kenney called “a little blip” in the late 1990s.
“That little blip is exactly the same thing that’s happening right now,” he said. “Survival rate didn’t change; that’s been relatively constant all the way through. What changes is the number of calves being born. At the end of the ’90s the number of calves born dropped off for three years. Since 2010, the number of calves has been lower than the number needed to replace the average mortalities in six of eight years, and just barely positive in the other two.”
Just five right whale calves were born this year, so the death of six whales last month ensures that the population will decline again, regardless of whether any other animals die during the rest of the year. Prior to the six deaths in the Gulf of St. Lawrence, one right whale died from a ship strike in April off Cape Cod, where the animals feed in late winter and early spring.
“The decline in the birth rate is more concerning now because climate change might have a hand in the changes taking place in the food supply,” Kenney said.
According to Kenney, the copepod that right whale’s eat, Calanus finmarchicus, may no longer be found in dense and long-lasting patches in the places the whales usually find them, due largely to warming ocean temperatures and changing currents and circulation patterns.
Kenney said one reason he is worried about the health of the right whale population is that “too many are still being killed that don’t have to be.”
In recent decades, most right whales have died from human causes — ship strikes or fishing-gear entanglement. The ship-strike issue has improved, thanks to regulations requiring ships to slow to 10 knots when traveling through areas where whales are known to reside. But the fishing-gear issue seems to be getting worse.
“The National Marine Fisheries Service has been nibbling at the edges of this issue for a long time because they aren’t willing to impose severe measures on the fishery,” Kenney said. “The agency responsible for promoting the fishery is the same agency responsible for regulating marine protected species. That was a dumb idea when it happened during the Nixon administration and it’s still a dumb idea today.”
The conservation community has proposed that fishermen be required to use ropes with a breaking strength of 1,700 pounds on their buoy lines in nearshore waters, and that the government support expanded testing of gear without any buoy lines. Research by the New England Aquarium and others on rope strength and the muscle power of whales has shown that most whales would be able to disentangle themselves by breaking 1,700-pound ropes. But fishermen are using stronger and stronger ropes. Some ropes removed from entangled whales had breaking strengths up to 12,000 pounds.
While Kenney is concerned about the right whale population, he is less concerned about the humpback whale population, despite the 47 humpbacks that have been found dead along the East Coast since 2016, including one that washed ashore on Jamestown and two on Cape Cod last month.
North Atlantic humpbacks were removed from the federal endangered species list last fall, and Kenney said that as the population increases, higher levels of natural and human-caused mortality are expected.
“Given the large number of live humpbacks along the Mid-Atlantic this winter, I suspect that there are more than the usual number of juveniles chasing food relatively close to shore — like the one that was seen repeatedly just off the Narragansett Pier seawall — and putting themselves in harm’s way,” he said. “Ship strike and entanglement mortality for all species is highest in juveniles.”
Rhode Island resident and author Todd McLeish runs a wildlife blog.