A recent study has found that critically endangered North Atlantic right whales are feeding closer to the ocean’s surface at night, increasing their risk of being struck by boats.
The study, published earlier this month in the peer-reviewed journal PLOS One, documented nighttime surface feeding in North Atlantic right whales, providing new evidence that could be used to prevent deadly collisions between the whales and vessels.
The paper’s lead author, Jay Kirkham, a PhD student at Dalhousie University in Halifax, said the research team worked with U.S.-based non-profit Ocean Alliance to tag 23 right whales in the Shediac Valley, an underwater valley in the southern Gulf of St. Lawrence.
A portion of the North Atlantic right whale population, which is estimated to be approximately 384 whales, gathers to feed in the Shediac Valley each summer.
Kirkham said the tags recorded video footage along with data on how the whales moved and in which direction they swam.
He said he used video footage to record right whale feeding behaviour during the day.
“When a right whale opens its mouth, it’s kind of like a big parachute opening on the front of their face … and that just slows them down an awful lot,” he said. “And so, they have to work harder, which they do by kicking their tail higher and faster.”
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Kirkham said he used these observations to train a machine learning algorithm that could recognize a right whale feeding at night when he was unable to visually identify the behaviour.
This data revealed that whales are feeding within the same depth as large vessels at night, increasing the risk of collision, he said.
While right whales typically feed close to the seafloor during the day, Kirkham said the whales follow their food — zooplankton — higher up in the water column at night.
“These big ships that go through the gulf, they extend into the water maybe 10, maybe 15 metres,” he said. “The whales are in a sort of vertical overlap with that.”
He said collisions with vessels and entanglements in fishing gear are the leading causes of death in the population and this study may help inform conservation measures for the whales.
Transport Canada and Fisheries and Oceans Canada currently oversee protection measures for the population.
In a statement to The Canadian Press, Fisheries and Oceans Canada said its measures focus on preventing whale entanglements in fishing gear and enforcing seasonal fishing closures.
The department said the study can help it develop “tailored management measures to protect North Atlantic right whales.”
Transport Canada implements speed restrictions and enforces a vessel exclusion zone in the Shediac Valley during the summer to reduce the risk of collisions between boats and right whales in the area.
However, Kirkham said that the whales he and his team tagged spent approximately 25 per cent of their feeding time outside of the vessel exclusion zone, exposing them to ship traffic.
In a statement to The Canadian Press, Transport Canada said it has a right whale surveillance program to help protect the whales from collisions by using both visual and audio detection tools.
“Acoustic monitoring systems and other complementary technologies can support whale detection regardless of daylight conditions and help inform protective measures when whales are present,” the statement said.
The department also said it uses the latest scientific research, monitoring data and feedback from stakeholders to inform its protection measures.
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