Abstract
This document provides technical updates and replaces the NMFS 2018 Revised Technical Guidance and is to be used for assessing the effects of underwater and in-air anthropogenic (human-made) sound on the hearing of marine mammal species under the jurisdiction of the National Marine Fisheries Service (NMFS). Specifically, it identifies the received levels and auditory weighting functions, or criteria, at which individual marine mammals are predicted to experience changes in their hearing sensitivity (either temporary or permanent) for acute (<24 hours), incidental exposure to underwater or in-air anthropogenic sound sources based on updated information. This Updated Technical Guidance may be used by NMFS analysts/managers and other relevant action ] proponents/interested parties, including other federal agencies, when seeking to determine whether and how their activities are expected to result in potential impacts to marine mammal hearing via acoustic exposure. This document outlines the development of NMFS’s criteria and describes how they will be updated in the future.
NMFS has compiled, interpreted, and synthesized the scientific literature, including a Technical Report by Dr. James J. Finneran (U.S. Navy-Naval Information Warfare Center Pacific (NIWC-PAC)) (Finneran 2024; Appendix A of this Updated Technical Guidance), to produce criteria for onset of temporary threshold shifts (TTS) and auditory injury (AUD INJ), which includes, but is not limited to, permanent threshold shifts (PTS) based on updated information. This document includes a protocol for the formation of marine mammal hearing groups (low- (LF), high- (HF), and very high- (VHF) frequency cetaceans, otariid (OW) and phocid (PW) pinnipeds in water, and otariid (OA) and phocid (PA) pinnipeds in air (Table ES1)), the derivation of marine mammal auditory weighting functions, and the estimation of AUD INJ onset criteria for impulsive (e.g., airguns, impact hammers, explosives) and non-impulsive (e.g., tactical sonar, vibratory hammers, drills) sound sources. These criteria are presented using dual metrics of weighted cumulative sound exposure level (SEL24h) and peak sound pressure level (PKSPL) for impulsive sounds and weighted SEL24h for non-impulsive sounds. These AUDINJ and TTS onset levels are treated as step functions (rather than dose-response criteria), where exposures above onset level are assumed to result in AUD INJ or TTS, while exposures below the onset level are assumed not to result in AUD INJ or TTS.
The Updated Technical Guidance’s criteria reflect the current state of scientific knowledge regarding the characteristics of sound that have the potential to impact marine mammal hearing sensitivity. NMFS recognizes that the implementation of marine mammal weighting functions and the weighted SEL24h criteria may extend beyond the capabilities of some action proponents. Thus, NMFS has developed an optional, alternative tool for those who cannot fully incorporate these factors into their own analyses (See Updated Technical Guidance’s companion optional User Spreadsheet tool).
These criteria do not represent the entirety of a comprehensive analysis of the effects of a proposed action, but rather serve as one tool (along with, e.g., behavioral disturbance criteria, auditory masking assessments, evaluations to help understand the ultimate effects of any particular type of impact on an individual’s fitness, population assessments, etc.) to help evaluate the effects of a proposed action and make the relevant findings required by NOAA’s various statutes. The Updated Technical Guidance may inform decisions related to mitigation and monitoring requirements, but it does not mandate any specific mitigation measures. The Updated Technical Guidance does not address or change NMFS’s application of these criteria in the regulatory context under applicable statutes and does not create or confer any rights for or on any person, or operate to bind the public. It only updates NMFS’s criteria based on the most recent science.
Independent peer review was required prior to broad public dissemination by the Federal Government. Details of the peer review, associated with the Updated Technical Guidance, are within this document (Appendix C).