Evaluating drivers of recent large whale strandings on the East Coast of the United States

Anthropogenic stressors threaten large whales globally. Effective management requires an understanding of where, when, and why threats are occurring. Strandings data provide key information on geographic hotspots of risk and the relative importance of various threats. There is currently considerable public interest in the increased frequency of large whale strandings occurring along the US East Coast of the United States since 2016. Interest is accentuated due to a purported link with offshore wind energy development. We reviewed spatiotemporal patterns of strandings, mortalities, and serious injuries of humpback whales (Megaptera novaeangliae), the species most frequently involved, for which the US government has declared an "unusual mortality event" (UME). Our analysis highlights the role of vessel strikes, exacerbated by recent changes in humpback whale distribution and vessel traffic.  Humpback whales have expanded into new foraging grounds in recent years. Mortalities due to vessel strikes have increased significantly in these newly occupied regions, which show high vessel traffic that also increased markedly during the UME. Surface feeding and feeding in shallow waters may have been contributing factors. We found no evidence that offshore wind development contributed to strandings or mortalities. This work highlights the need to consider behavioral, ecological, and anthropogenic factors to determine the drivers of mortality and serious injury in large whales and to provide informed guidance to decision-makers.

Maritime transportation: Let's slow down a bit

Maritime transportation is a major contributor to the world economy, but has significant social and environmental impacts. Each impact calls for different technical or operational solutions. Amongst these solutions, we found that speed reduction measures appear to mitigate several issues: (1) collision with wildlife; (2) collision with non-living objects; (3) underwater noise; (4) invasive species; and (5) gas emission. We do not pretend that speed reduction is the best solution for each individual issue mentioned in this paper, but we argue that it could be a key solution to significantly reduce these threats all together. Further interdisciplinary research is required to balance private economic costs of speed reduction measures with environmental and social benefits emerging from all mitigated issues.

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

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.