Methods for studying large whales fall into the following general categories: visual observations via boat or aircraft; underwater acoustics to record whale calls and other vocalizations and clicks; physiological and biological sampling to understand more about whales’ health, such as stress levels, reproductive status, and diet; biologging or tagging animals to gather information about their movements and behavior; and resighting of individual animals (e.g., cataloging) to monitor individuals over long periods of time. Permits are required to ensure that scientific research on whales is conducted by highly experienced scientists and is as safe as possible. Research scientists and natural resource managers carefully consider which methodologies may be able to answer their specific research question with the least possible impact to the animals.

Studying the habitat and movement of whales can be difficult as they spend considerable amounts of time below the surface, out of sight. Satellite tags can help researchers understand where whales go when they are not visible (e.g., when they are underwater, inhabiting understudied or novel habitats, at night, in bad weather, etc.). However, researchers must also consider the potential for negative impacts of tagging. Research on whales using tags requires permits under the Marine Mammal Protection Act (MMPA) and the Endangered Species Act (ESA). Decisions regarding whether to deploy a tag on an individual, the type of tag attachment, and other logistical decisions depend on a number of factors, including the animal’s health and age class, the size of its population (e.g., the importance of the individual to maintaining the population), other existing risk factors like vessel strike and entanglement, species-specific impacts, and gaps in available scientific data for the species. Ultimately, the decision to deploy tags depends on the relative benefit of obtaining tag data compared to other data collection means, specifically regarding whether the scientific questions can be answered with less invasive methods. Tags are generally divided into two categories, non-invasive tags that are for short-term studies that generally use suction cups or other exterior attachment methods and invasive tags that are anchored to the skin or implanted for longer-term deployments. Care is taken to ensure that tag designs and choices should not risk the health, welfare, and reproductive status of the tagged animal.

Humans and marine mammals experience sound differently because air and water have different physical properties that influence sound propagation and because we have different anatomies for hearing and producing sound living above- vs. underwater. Sound travels much faster and farther in water than it does in air due to the different densities of the two mediums. In general, human and marine mammal hearing are optimized for different frequency ranges.

Protected Species Observers (PSOs) are trained professionals who monitor marine animals that are federally protected under the Endangered Species Act (ESA) and/or Marine Mammal Protection Act (MMPA). This monitoring occurs in relation to anthropogenic activities and helps a wide range of entities comply with federal requirements. There is a certification process and standards for PSO training, and credentials of individuals are reviewed by NOAA Fisheries for specific projects to ensure they have appropriate training and/or experience to perform the necessary duties. PSOs collect data to inform implementation of marine mammal mitigation measures for a variety of activities associated with offshore wind energy development and to enhance the understanding of potential offshore wind impacts on marine mammals. Data include sightings of live, entangled, or dead marine mammals; marine mammal sightings to inform implementation of a mitigation measure (such as changing a vessel speed/trajectory or shutting down a sound-generating activity when animals are present in the vicinity); a record of PSO observation effort and methods; and offshore wind farm operations data (e.g., project name, location, details about active acoustic sources). The federal agencies who receive PSO data and reports from offshore wind projects include NOAA Fisheries, the Bureau of Ocean Energy Management (BOEM), and the Bureau of Safety and Environmental Enforcement (BSEE).

Protected Species Observers (PSOs) are trained professionals who implement a range of mitigation and monitoring measures to reduce impacts to protected species from human activities. PSOs also collect data to support broader federal agency goals (e.g., recording sightings of live, entangled, or dead marine mammals). While the main focus of PSOs is to monitor for protected species and implement mitigation measures, as required, PSO data can also theoretically be used to help inform our understanding of species presence, abundance, and distributions, though limitations exist on the utility of this data for broader research purposes. A recent scientific publication (Ganley et al. 2024) examined publicly available PSO data related to offshore wind energy development from 2017–2022 and indicated that data formatting and reporting protocols were not standardized; therefore, PSO data could not be used to meet broader scientific goals. Data formatting and standardization processes for PSO data reporting have improved since 2022. Offshore wind developers are required to submit all PSO datasets and summary reports to NOAA Fisheries. However, not all data have been made publicly available on the NOAA website (as of November 2024).

There are various ways in which offshore wind developers may be involved with research and monitoring, including (1) monitoring for the purposes of mitigation and (2) monitoring and research to understand baselines and potential effects, which may be funded by individual developers or other groups, for which developers contribute site access, staff time, and/or other resources. Major types of marine mammal monitoring and research activities conducted in relation to offshore wind energy development include passive acoustic monitoring (PAM), use of Protected Species Observers (PSOs), near-real time incidental reporting of important sightings, boat-based and aerial surveys, biologging (e.g., individual tracking using GPS tags or other transmitters), and biological sampling. Federal agencies, state agencies, and regional science groups generally recommend that all marine mammal data collected by developers be made publicly available. Monitoring datacollected as part of federal permitting are shared with federal agencies and made publicly available. However, data sharing can be complicated in cases where there is no public database for a particular type of data.