Regulating Impacts of Noise on Marine Mammals in North America: An Overview of the Legal Frameworks in Canada and the United States

Abstract Marine mammals are protected under dedicated taxonomic legislation, endangered species legislation, and general environmental stewardship laws in many countries. Governments and agencies within those countries are tasked with assessing and limiting human impacts in accordance with their own laws, including those arising from underwater noise emissions. While the United States (US) has established thresholds for permanent and temporary threshold shifts (PTS and TTS) in the hearing of marine mammals, Canada has not yet established specific numeric onset thresholds for hearing impairment or other noise-related impacts. Given that Canada and the US are jointly responsible for the management of a number of at-risk marine mammals, we provide a brief overview of the main laws and associated standards relevant to management of noise impacts on marine mammals in these two jurisdictions. The US PTS/TTS thresholds are only a small part of a suite of elements collectively applied to assess and mitigate the full range of impacts of noise on marine mammals, and the implementation of these (or any other) thresholds in Canada would not negate the need to conduct case-specific impact assessments to satisfy their own broader requirements. Caution should be taken when applying US thresholds to address Canadian legal standards, as there are substantial differences in the legal definitions to which these thresholds might be applied. Thus, the need for, and application of, similar generalised PTS/TTS thresholds in Canada is still under debate and noise impacts will likely continue to be assessed in different ways in these two bordering nations.