Ship Noises Disturb Southern Resident Killer Whale Sound Systems

Summary: Ship noises disturb Southern Resident killer whale sound systems, according to a first-ever maritime traffic impact study published Feb. 2 in PeerJ.

Male orca "Ruffles" uses echolocation to find his favorite food, Chinook salmon, as a tanker approaches him in Haro Strait, offshore from Washington state's San Juan Islands archipelago: beamreach.org, CC BY SA, via EurekAlert!

Published in PeerJ Feb. 2, 2016, a first-ever study of maritime traffic impacts finds that, for 28 months, from March 2011 to Oct. 2013, ship noises disturb Southern Resident killer whale sound systems used for communication and echolocation in the Pacific Northwest’s Haro Strait.

“This is the first study to present source spectra for populations of different ship classes operating in coastal habitats, including at higher frequencies used by killer whales for both communication and echolocation,” note the three co-authors in their online, peer-reviewed article, “Ship Noise Extends to Frequencies Used for Echolocation by Endangered Killer Whales.”

The study tracks 2,809 isolated transits by 1,582 unique ships through the “core critical habitat” of the endangered Southern Resident killer whale, the Haro Strait, between Canada’s Vancouver Island and Washington state’s San Juan Island. The Haro Strait connects the Strait of Georgia to the Strait of Juan de Fuca as a critical part of the international boundary route between Canada and the United States.

As a major shipping channel, the Haro Strait is awash with noise pollution, especially the noise radiated underwater at a range of low to high frequencies. The study’s 12 different general ship classes register a spectrum low of 100 hertz (Hz) and a high of 96,000 Hz. Background noise levels received near the Haro Strait’s shoreline range from 11.5 to 40,000 Hz.

The study’s cutoff low-high parameters of 20 Hz to 96,000 Hz, respectively, encompass Southern Resident killer whale sound systems that favor middle to high frequencies. Southern Resident killer whale sound systems display most sensitivity near 20,000 Hz, the upper range of social vocalizations and the lower range of echolocation clicks. The endangered species’ whistle sounds at 2,000 to 16,000 Hz.

“Having ensured our samples were isolated (uncontaminated by noise from other ships or boats) and subtracted estimated background levels, we are confident that median received levels of ship noise in the core of SRKW critical habitat are elevated above median background levels not only at low frequencies (20-30 dB from 100 to 1,000 Hz), but also at high frequencies (5-13 dB from 10,000 to 40,000 Hz),” lead author Scott Veirs, program coordinator and professor at Seattle’s Beam Reach Marine Science and Sustainability School, and co-authors Val Veirs, retired Colorado College physics professor and Scott’s father, and Jason D. Wood, manager of San Juan Island’s SMRU Consulting, report in the articles “Conclusions.”

Frequent transits of Haro Strait by Southern Resident killer whales often place the endangered species within 10 to 300 meters (32.8 to 984.25 feet) of the Lime Kiln Point lighthouse on San Juan Island’s mid-western shoreline. The fish-eating orcas, with high partiality for Chinook salmon, find themselves about 2 kilometers (1.24 miles) from the center of the nearest shipping lane, transited by northbound vessels. A calibrated hydrophone deployed 50 meters (164 feet) offshore, at 2.25 kilometers (1.398 miles) from the center of the northbound lane, identifies the study site.

The study’s three co-authors note that military ships radiate the least disturbing amount of noise whereas container ship noises intensify at all frequencies. Lead author Scott Viers shares his hope for the public takeaway from the study’s finding that ship noises disturb Southern Resident killer whale sound systems.

“Ships are one of the major sources of noise in the ocean and may grow to dominate many marine soundscapes if the growth of the global fleet is unchecked. The good news, though, is that it may be possible to mitigate much of the ship noise, either by transferring quieting technologies from military to commercial fleets, or making operational changes -- like slowing down,” Scott Veirs tells the study’s publisher, PeerJ, in an interview on Feb. 2, 2016.

Figure 1: Study site map ~ Inset regional map shows study area (black rectangle) and shipping lanes (in red) leading to Salish Sea's major ports. The 240 degree bearing (gray arrow) extends from Lime Kiln hydrophone (gray circle) through northbound shipping lane. Bathymetric contours (50 meters) show Haro Strait as steep-sided 200 to 300 meter-deep channel. Sound projection locations (black dots) are sites used for transmission loss (geometric spreading + frequency-dependent absorption) experiment; Scott Viers, Val Veirs and Jason Wood "Ship noise extends to frequencies used for echolocation by endangered killer whales," PeerJ (Feb. 2, 2016), figure 1: CC BY 4.0 International, via PeerJ

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Male orca "Ruffles" uses echolocation to find his favorite food, Chinook salmon, as a tanker approaches him in Haro Strait, offshore from Washington state's San Juan Islands archipelago: beamreach.org, CC BY SA, via EurekAlert! @ https://www.eurekalert.org/multimedia/604727; EurekAlert! news release URL @ https://www.eurekalert.org/news-releases/599117; (former URL @ http://www.eurekalert.org/multimedia/pub/107691.php?from=317503)

Figure 1: Study site map ~ Inset regional map shows study area (black rectangle) and shipping lanes (in red) leading to Salish Sea's major ports. The 240 degree bearing (gray arrow) extends from Lime Kiln hydrophone (gray circle) through northbound shipping lane. Bathymetric contours (50 meters) show Haro Strait as steep-sided 200 to 300 meter-deep channel. Sound projection locations (black dots) are sites used for transmission loss (geometric spreading + frequency-dependent absorption) experiment; Scott Viers, Val Veirs and Jason Wood "Ship noise extends to frequencies used for echolocation by endangered killer whales," PeerJ (Feb. 2, 2016), figure 1: CC BY 4.0 International, via PeerJ @ https://peerj.com/articles/1657/

For further information:

"Endangered and Threatened Wildlife and Plants: Endangered Status for Southern Resident Killer Whales. Final Rule." Federal Register, vol. 70, no. 222 (Nov. 18, 2005): 69903-69912.
Available @ http://www.fisheries.noaa.gov/pr/pdfs/fr/fr70-69903.pdf

Kellen, David. "Ship Noises Severely Impact Killer Whale Population." Lighthouse News Daily. Feb. 4, 2016.
Available @ http://www.lighthousenewsdaily.com/ship-noises-severely-impact-killer-whale-populations/4288/

"Killer whale (Orcinus orca)." NOAA Fisheries > Protected Resources > Species.
Available @ http://www.nmfs.noaa.gov/pr/species/mammals/whales/killer-whale.html

Megiston. "Killer whales are struggling to hear each other in the Pacific Ocean." YouTube. Feb. 2, 2016.
Available @ http://www.youtube.com/watch?v=NoM_Ty80eHc

PeerJ -- the journal @thePeerJ. "Ship noise extends to frequencies used for echolocation by endangered killer whales." Twitter. Feb. 2, 2016.
Available @ https://twitter.com/thePeerJ/status/694581102204186624

PeerJ. "Ship noise extends to frequencies used by endangered killer whales." PeerJ press release. Embargoed until Feb. 2, 2016.
Available via PeerJ @ http://static.peerj.com/pressReleases/2016/Press-Release-Veirs.pdf

"Ship noise extends to frequencies used by endangered killer whales." EurekAlert! > Public Release. Feb. 2, 2015.
Available via EurekAlert! @ https://www.eurekalert.org/news-releases/599117
Available via EurekAlert! @ http://www.eurekalert.org/pub_releases/2016-02/p-sne012716.php (former URL)

"Ship noise frequencies heard by killer whales -- Author Interview." PeerJ Blog. Feb. 2, 2016.
Available via PeerJ @ https://peerj.com/blog/post/115284878599/scott-veirs-orca-ship-noise/

Veirs, Scott, Val Veirs and Jason D. Wood. "Ship noise extends to frequencies used for echolocation by endangered killer whales." PeerJ. Published Feb. 2, 2016. DOI: 10.7717/peerj.1657
Available via PeerJ @ https://peerj.com/articles/1657/