||| FROM KUOW.ORG |||
Orca conservation groups are thanking commercial ships and other big vessels for slowing down around endangered southern resident killer whales.
They are asking vessels to voluntarily reduce their speeds in a section of Puget Sound where orcas are often present. It’s a 22 nautical mile long stretch that reaches from Port Townsend to Edmonds and Everett. Researchers believe this area is where killer whales are most likely to spend their time when in Puget Sound.
A map of the slowdown area. Quiet Sound
Rachel Aronson is the director of Quiet Sound, the group that organized the slowdown. She says the propellers of large ships create a lot of noise.
“When the propeller spins, it creates teeny little bubbles, and the explosion and collapse of those bubbles is called cavitation, Aronson said. “That cavitation can be surprisingly loud in the frequencies that killer whales need to echolocate, and communicate.”
Organizers are asking large vessels to reduce their speeds by 30-50%. Container vessels, vehicle carriers, and cruise ships are asked to drop speeds to 14.5 knots, while tankers and bulkers are asked to slow to 11 knots in the slowdown area. Aronson said when vessels slow down to a target speed, it can reduce underwater noise pollution by 45%.
