A dramatic drop in marine traffic caused by the COVID-19 pandemic has created what scientists call a rare opportunity to investigate how the calmer waters affect southern resident killer whales off the coast of British Columbia.
Ocean Networks Canada, which monitors ship noise and sounds from marine mammals such as orcas, said it believed the change would be a boon for the animals.
“The anticipation is that the quieter environment will help killer whales to communicate, socialize, navigate and most importantly, find food,” said Richard Dewey, deputy director of organizational science.
An article published last month in the Journal of the Acoustical Society of America reported that there was an approximately 30% decrease in commercial shipping traffic to the Port of Vancouver from China due to COVID-19 in during the first four months of the year.
Dewey said it is not only the commercial traffic that has decreased – there has also been a break in whale watching boats, cruise ships, pleasure boats and tankers. This led to a reduction in noise by
about 75%, he said.
“What we are seeing in the Salish Sea are levels of navigation noise that have not been present for three or four decades,” he said.
“So we would have to go back to the 80s before hearing such a calm environment.”
Calmer oceans, a boon for researchers and whale orcas
One of the main concerns of endangered southern killer whales is that shipping noise is increasing and doubling almost every decade, he said.
These mammals have a hearing similar to that of humans and they communicate in a frequency band similar to ours, said Dewey.
They use vocalizations to communicate inside the pod, to navigate and especially to find their prey, he said.
“They find their way around to find their salmon. It is a kind of very sophisticated acoustic capacity and the quieter the environment, they would be more successful in finding prey. “
In the ocean, Dewey said that whales use sound “continuously and all the time”.
Their sight helps them to see from a distance of about five to 10 meters while the use of sounds helps them to travel miles, he said, adding that the Salish Sea is a “very trouble”.
Scientists believe loud noises from humans increase stress hormones in killer whales because they have to cry and can’t communicate over long distances, said Dewey.
He compared him to someone entering a noisy club and having to pause until the noise passed, to speak louder or to give up.
He noted that unlike people in a club, orcas can’t just leave for a quieter space.
New restrictions on navigation around orcas off the coast of British Columbia
Scientists will use 30 hydrophones to record the sounds of orcas when they arrive in the Salish Sea, which should happen at any time, said Dewey.
Hydrophones are underwater recording devices that record how loud the whales speak when they are noisy or when they give up.
The team hopes that this study will provide the data needed to make policy and regulatory changes to help the animals survive, he said.
“If we see them coming back and staying in their critical habitat for longer periods of time … if we have evidence of a successful salmon diet, then these are all good signs and, in a sense, the more calm can only have helped their survival, “he said. .
The director of the marine mammal research unit at the University of British Columbia said that in the past, orcas have been seen in the Salish Sea in May and June, but that for four years they have arrived much later, sometimes as late as September.
Andrew Trites said that one of the reasons could be that there is not enough salmon, although mathematically there are enough fish for the 72 southern killer whales.
This left scientists wondering if the problem is that whales cannot hunt due to disturbance from ships, he said.
“And it is possible to see if the behavior of the whales is different with fewer boats on the water and less noise.”
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