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ESR 44:177-201 (2021)  -  DOI: https://doi.org/10.3354/esr01093

Co-occurrence of gray whales and vessel traffic in the North Pacific Ocean

Gregory K. Silber1,*, David W. Weller2, Randall R. Reeves3, Jeffrey D. Adams4, Thomas J. Moore5

1Smultea Environmental Sciences, Washington Grove, MD 20880, USA
2Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, NOAA, La Jolla, CA 92037, USA
3Okapi Wildlife Associates, Hudson, Quebec J0P1H0, Canada
4Office of Protected Resources, National Marine Fisheries Service, NOAA, Silver Spring, MD 20910, USA
5Independent Researcher, Seattle, WA, USA
*Corresponding author:

ABSTRACT: All species of large whales are susceptible to vessel strikes, but the true scale and geographical extent of such strikes is not known. This paper provides a qualitative assessment of the range-wide risks posed to gray whales Eschrichtius robustus by vessels, by comparing patterns of whale distribution with the density of vessel traffic seasonally throughout the North Pacific in 2019. Areas of very high vessel density were evident year-round near many coastlines, along inter-continental trade routes, and at hubs of commercial shipping near port entrances. Gray whales were exposed to vessel strikes throughout their range and in their feeding, southbound migration, wintering, and northbound migration periods. Areas of apparently high risk were in the Russian Far East (Kamchatka peninsula and Okhotsk Sea), Bering Sea (including the Aleutian Islands), Gulf of Alaska, and along the entire west coast of North America. Risk appeared greatest during south- and northbound migration when much of the gray whale population is moving through waters near shore. Tanker, container, and bulk-carrier ships represent considerable risk to whales in the North Pacific Ocean, but the large geographical extent of commercial fishing activities suggests that fisheries are also a substantial source of risk. Vessel-strike risk maps indicate the relative extent of exposure of gray (and other) whales to underwater vessel noise. The number of gray whales killed by ship strikes each year may be in the tens, or perhaps the low hundreds. Additional analyses, including quantitative assessments, are warranted to further clarify the risk of vessel strikes to gray whales.


KEY WORDS: Vessel-strike risk · Gray whale · Eschrichtius robustus · Ship strike · Vessel traffic · Spatio-temporal co-occurrence


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Cite this article as: Silber GK, Weller DW, Reeves RR, Adams JD, Moore TJ (2021) Co-occurrence of gray whales and vessel traffic in the North Pacific Ocean. Endang Species Res 44:177-201. https://doi.org/10.3354/esr01093

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