Kristen Kanes is watching for the signature sounds that will mark the return of the southern resident killer whales to their seasonal feeding grounds in the Salish Sea. The clicks, whistles and complex calls are picked up on hydrophones in a string of undersea observatories.
The killer whales, or orca, are due back in these waters between Washington State and British Columbia any day now, and researchers are watching for changes when they return for the summer and fall to hunt for salmon. A marked reduction in marine traffic due to the pandemic has created a quieter environment, and if they can document a positive change for the endangered orca, it could help regulators on both sides of the border to enforce noise-reduction measures even after marine vessel traffic rebounds.
A scientist with Ocean Networks Canada, Ms. Kanes specializes in recognizing orca communications. The southern residents share a set of calls, but each of the three pods that make up this dwindling population have distinct accents, allowing her to distinguish the family units by their vocalizations. It’s too time-consuming to listen in real time, so she picks out the patterns in spectograms – visual representations of the sounds they make.
“The pulsed calls of the southern residents in particular often sound like kittens mewling,” Ms. Kanes says. On paper, that call looks like a stack of curvy lines.
Until recently, underwater noise in the North Pacific has been doubling every decade since the 1950s. Since January, the pandemic has reversed the trend. The reduction in marine traffic in the Pacific Ocean, from large container ships to small whale-watching vessels, is providing a unique opportunity to measure whether quieter seas will help these endangered marine mammals.
The pandemic has led to a slowdown in global economic activity, including a decrease of as much as 30 per cent in the number of container ships going from China to the Port of Vancouver during the first four months of the year. That means the orca may not need to shout to each other to communicate, and while chinook stocks from the Fraser and Skagit rivers have been inexorably declining, it might be easier for the pods to find their key source of food this year.
A Dalhousie University study used data from the Ocean Networks Canada network of cabled undersea observatories to track the output of four hydrophone stations during that time. The Dalhousie report, published in May in The Journal of the Acoustical Society of America, confirmed a reduction in underwater noise commensurate with the economic slowdown.
Now, researchers are waiting for the orca to return to the Salish Sea so they can study whether the southern residents – who are in decline because of starvation, pollution and underwater noise from ships – are better off as a result.
Richard Dewey, the Ocean Networks associate director of science, says tracking is continuing, and the data from May show a continued, substantial reduction in noise, particularly in the Strait of Georgia. It’s not just container ship traffic that has declined due to COVID; the number of ferry sailings is also down, while whale-watching boats and cruise ships have been idled.
The next step is to look for a response in the southern resident killer whales. “Can we actually see them behaving a little bit more relaxed? Can we detect from samples in the water a reduced stress level? And if we can put that story together, I think it really would give us a strong case to continue efforts like reducing ship speed. That would help reduce the background noise even if we were to get back to full commerce,” he says.
“I think we’re all anxious, in a sort of very hopeful way, to see this. Maybe for the first time in some of their lives, they will experience a Salish Sea that is quieter than they’ve experienced before – a Salish Sea that is a bit better.”
The southern resident killer whales’ Pacific Ocean habitat ranges from California to Alaska, and they are recognized as endangered in Canada and the United States. At last count, there were just 73 animals – technically dolphins – left. They feed almost exclusively on chinook salmon and rely on echolocation to hunt, which is difficult when sound is muddied by the loud throbbing of propellers.
Marine wildlife veterinarian Joe Gaydos says researchers have found that over the years, the increasing level of underwater noise from vessel traffic has forced the orca to change their communications.
“When the noise level goes up around them, they have to do the same thing that we do at a loud party or a concert – they speak slower and louder,” he says. “These animals, they’re acoustic. ... They hear things that you and I can never even imagine what it’s like to hear.”
Dr. Gaydos is science director of the SeaDoc Society at the University of California, Davis, which sponsors research in the inland waters of the Pacific Northwest, also known as the Salish Sea. He was part of the scientific team that attempted an unprecedented cross-border rescue mission in 2018 to try to treat and feed a starving member of J pod, one of the three family groups in the southern resident killer whale population. The orca, known as Scarlet, was later declared dead.
He is hopeful the quieter seas will help the orca, even when chinook are in short supply. “If they’re able to find more of those salmon, they’re going to put on more weight,” he says. “They’re going to have better reproductive success. They’re going to have better ability to fight off disease.” And if this summer turns out to be a better year for the southern residents, there’s a chance policymakers in the U.S. and Canada will commit to engineering reductions even after their economies, and marine shipping, rebound.
“If we have an opportunity to try and learn something from this, we’d be fools not to take advantage of it,” he says.
Kate Moran, president and chief executive officer of Ocean Networks Canada, has spent years working to reduce the impact of human activity on ocean life, and she spearheaded efforts to launch a voluntary vessel slowdown trial in the waters outside the Port of Vancouver, an important summer feeding area for southern resident killer whales.
She says the vessel slowdown has been successful in helping reduce some of the noise pollution in the Salish, but she says the marked drop in noise this year shows the way forward. “COVID-19 has demonstrated that the fewer the ships, the less noise there is. That’s really the big way to reduce the noise.”
What she hopes to see from the next stage of research is whether scientists can document a benefit to marine life from the reduction in noise.
“If that can be demonstrated, then that evidence will make it much more powerful for industry to actually make more efforts to reduce noise, and perhaps even in a regulatory environment,” says Dr. Moran, “that would be information that could inform policy.”
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