| Summary: | Commercial ships are a dominant source of noise throughout much of the world’s oceans, raising concern about the degradation of acoustic habitat for marine mammals and other species. In the Salish Sea, noise from bulk carriers, container ships, tankers, vehicle carriers, fishing boats, and other vessels extends from the low frequencies used by baleen whales to the higher frequencies used by killer whales. To manage this growing problem, various experts and expert groups have proposed focusing mitigation efforts on the noisiest vessels, because they assume or estimate that a relatively small number of outliers are contributing disproportionately to the total acoustic energy produced by commercial ships. This study tests that hypothesis using one of the largest existing sets of shipping noise data: a record of 1,582 unique ships that transited Haro Strait between 2011 and 2013. We show how noise output is distributed for the various types of commercial vessels that use the Salish Sea, define a class of “gross polluters,” and determine, through quantitative analysis, whether quieting these very loudest ships could achieve the 3 dB and 10 dB reduction targets (in acoustic energy) endorsed by the Scientific Committee of the International Whaling Commission in 2008. Finally, we consider the implications of our findings for managing low- and higher-frequency ocean noise in the Salish Sea.
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