A letter signed by 16 regional scientists and sent to leaders on both sides of the border March 1 asking for silencing of military sonar in the Salish Sea was especially timely as another sonar incident occurred on February 29.
Washington State Ferries Operations Center called the Whale Museum to report ferry workers and passengers on the Clinton-Mukilteo route heard sonar sounds above water.
More information about the incident is available here.
The open letter was motivated by the Feb 6, 2012, use of sonar by the Canadian Navy in U.S. critical habitat of the endangered southern resident killer whales, and the observation 36 hours later of southern residents in Discovery Bay where they had never before been sighted.
The letter signed by scientists who research killer whales is posted below.
As biologists and bioacousticians who study killer whales of the Salish Sea, we ask that the U.S. Navy and Canadian Navy cease using sonar in their critical habitat. Polluting their environment with intense underwater noise like the “pings” from mid-frequency active sonar poses significant risks to these Federally-listed species. On February 6, 2012, the Canadian Naval frigate HMCS Ottawa used its sonar system in critical habitat of the endangered Southern Resident Killer Whales during a training exercise east of Victoria, B.C. The calls of the Southern Residents’ K and L pods were heard 18 hours later in Haro Strait, and sub-groups of K and L pods were identified 36 hours after the sonar use in Discovery Bay – a location where Southern Residents have never been sighted in 22 years of records.
These observations are reminiscent of an incident in May, 2003, when the USS Shoup’s sonar training exercise caused similar unusual nearshore surface milling behavior of Southern Residents in Haro Strait. New limits should be put on the use of mid-frequency active (MFA) sonar, particularly in the critical habitat of the Southern Residents. Killer whales are sensitive to the frequencies emitted by MFA sonar (2-10 kHz) and use the same frequency range to communicate with calls and whistles.
Because MFA sonar is intense (source levels ~220-235 underwater decibels), it could permanently or temporarily deafen whales that are unexpectedly nearby and thereby impact their ability to forage, navigate, and socialize. Even temporary threshold shifts could be deleterious because the recovery of the Southern Residents hinges on their use of echolocation to find, identify, and acquire their primary prey, Pacific salmon.
Current procedures for mitigating underwater military noise are inadequate to protect either the resident or transient ecotypes. These procedures depend on the ability to detect whales within 1000 yards (U.S.) or 4000 yards (Canada), which neither passive acoustic listening nor visual surveillance can reliably accomplish.
The unprecedented sighting of Southern Residents in Discovery Bay suggests that they may have been present during the pre-dawn sonar exercise on February 6 while remaining undetected by the Canadian Navy’s marine mammal monitoring procedures. Moreover, we know from the 2003 Shoup incident and the scientific literature that MFA sonar can disrupt marine mammal behavior well beyond the current mitigation distances, particularly in the sound propagation conditions of the Salish Sea.
We therefore urge the U.S. and Canadian Navies to restrict MFA sonar and other intense underwater sound sources in all training and testing conducted in the Salish Sea. By protecting the whales’ acoustic habitat, our Navies can help further their respective country’s obligations to ensure the recovery of these endangered iconic populations while still fulfilling their important National security missions.
David Bain, Ph.D
Robin Baird, Research Biologist, Cascadia Research Collective
John Calambokidis, Research Biologist, Cascadia Research Collective
Fred Felleman, Vice-President, Board of Directors, The Whale Museum
Andrew Foote, Postdoctoral Fellow, University of Copenhagen, Denmark
Rachael Griffin, B.Sc. Marine Biology, Aquagreen Marine Research, Victoria, BC
Erin Heydenreich, Field Biologist, Senior staff at the Center for Whale Research
Cara Lachmuth, MSc., Contract Biologist, Victoria, BC
Patrick Miller, Lecturer, School of Biology, University of St Andrews, Scotland
Richard Osborne, Ph.D., Research Associate, The Whale Museum
Paul Spong, Director, OrcaLab and Pacific Orca Society, Alert Bay, BC
Helena Symonds, Director, OrcaLab and Pacific Orca Society, Alert Bay, BC
Scott Veirs, President, Beam Reach Marine Science and Sustainability School
Val Veirs, Professor of Physics, Colorado College
Monika Wieland, BA in Biology, Reed College
Jason Wood, Ph.D., Research Associate, The Whale Museum