There are a multitude of factors threatening the Southern Resident killer whale (SRKW) population in the Salish Sea—water contamination, a lack of Chinook salmon (SRKW food of choice), and the lingering effects of live captures for aquariums in the 1960s have all led the whale population to struggle, leaving  only 74.

One of the main concerns highlighted by scientists is noise below the waves, caused by commercial ships and recreational boats. 

In April, scientists sounded the alarm with a study showing the population is on a fast track to extinction.

A study published last week in Global Change Biology highlights the specific effects noise can have on the survival of both Northern and Southern Resident orcas.

The team of researchers—including representatives from the DFO, Wild Orca, the Cascadia Research Collective and the University of Cumbria in the UK—collected foraging data on both population of killer whales and the ambient noise in the Salish Sea, with recordings starting in 2009.

While conservationists have worked to reduce the noise by pushing for slower speeds—the faster a boat goes, the noisier it becomes—and directing ships away from typical SRKW hunting grounds, the din of noise has increased alongside the rise in commercial vessels in the Salish Sea, according to the study.

Northern and Southern Resident orcas search for food via echolocation, using a series of clicks and buzzes to identify their food and communicate with each other in group hunts. When the ambient noise in the ocean becomes too loud, they’re no longer able to hear themselves or the bounceback from echolocation. 

What’s worse, the orcas don’t give up the hunt—they simply try harder to no avail. The study found that these whales expend more energy and burn more calories while hunting in noisy areas, but they don’t collect enough food to meet that expenditure. 

This becomes a deeper issue when looking at differences between the sexes of the whales—females were less likely to pursue a hunt in noisy areas than males. This could be a contributing factor to calf mortality, since mothers need an increased amount of calories to nurse their young. If they’re not able to get enough food, both the mother and calf will suffer. This lack of calorie intake in females could also be linked to the high rate of failed pregnancies among SRKW, according to the study’s author.

Males are also able to hold their breath longer than females, allowing them to swim deeper to get away from the noise. But even these deep dives were not found to be particularly effective when the noise levels increased.

Rob Williams from the Ocean Initiative in Washington spoke with Capital Daily in April to discuss his team’s research on the struggling SRKW. While he said that reducing noise won’t address the lack of Chinook salmon, it will improve the hunting skills of SRKW, allowing them to hunt more efficiently. Williams and his wife Erin, who both founded Ocean Initiative, have been integral in helping governments in Vancouver and Seattle identify key hunting routes of SRKW to launch ship slowdown laws in both ports.

“We have known this stuff for well over a decade,” Williams said. “The alarms were raised about the extreme specialization of Southern Resident killer whales function of salmon.”

“There isn't time to waste. We have one generation to turn this around and if we don't, we will lose the population.”

While the authors of the recent study write that “the timescales for recovering prey populations may span decades,” their research has found that specific actions to reduce noise in the short term “could offer a critical pathway for bolstering odontocete [toothed whales] foraging opportunities globally.”

In June, Canada committed to new protections for SRKW and NRKW, with sanctuary zones, fishing bans, and speed reductions set to roll out by next year. Local whale watching companies have agreed not to offer tours that follow SRKW and all vessels must remain 400m away from all killer whales. Commercial and recreational salmon fisheries will close in key SRKW foraging areas for the rest of 2024 and all of 2025.

Transport Canada has committed more than $3M over the next two years to the Enhancing Cetacean Habitat and Observation (ECHO) Program, led by the Vancouver Fraser Port Authority, which focuses on curbing the noise of ships moving through Vancouver waters. The DFO is also considering making changes to the Marine Mammals Act in the next year.