NOAA Fisheries has issued regulations and a letter of authorization (LOA) to the U.S. Navy that require protective measures to minimize impacts to marine mammals while conducting training and testing activities in the Mariana Islands Training and Testing Study Area in the South Pacific.
The Navy requested an authorization under the Marine Mammal Protection Act (MMPA) because the sound generated by mid-frequency active sonar and the pressure generated by detonating explosives may affect the behavior of some marine mammals or cause temporary loss of their hearing sensitivity or other injury.
The Navy is currently operating under a rulemaking that NOAA Fisheries issued in 2010 for the Mariana Islands Range Complex. Since then, the Navy has submitted annual monitoring and exercise reports, which are available to the public and on the Navy website.
They are required to renew their MMPA authorization every five years.
Under the authorization the Navy is required to follow mitigation measures to minimize effects on marine mammals including:
- Establishing marine mammal safety zones around each vessel using sonar;
- Using Navy observers to shut down sonar operations if marine mammals are seen within designated safety zones;
- Using exclusion zones, to ensure that explosives are not detonated when animals are detected within a certain distance; and
- Implementing a stranding response plan that includes a training shutdown provision in certain circumstances and allows for the Navy to contribute in-kind services to NOAA Fisheries if the agency has to conduct a stranding response and investigation.
No mortality is anticipated or authorized, and the measures included in the final rule should minimize the potential for injury, and significantly reduce the number of marine mammals exposed to levels of sound likely to cause behavioral reactions and temporary loss of hearing sensitivity. Additionally, the final rule includes an adaptive management component that requires that the Navy and NOAA Fisheries to meet yearly to discuss new science, Navy research and development, and Navy monitoring results to determine if modifications to mitigation or monitoring measures are appropriate.
NOAA Fisheries and the Navy have worked to develop a robust monitoring plan that includes extensive survey and photo-identification databases that will strengthen the marine mammal density and distribution data available in the Mariana Islands. Additionally, the Navy has developed (with input from NOAA Fisheries) an integrated comprehensive monitoring plan to prioritize monitoring goals and standardize data collection methods across all of their U.S. range complexes.
The Navy has been conducting training exercises, including the use of mid-frequency sonar, in the Mariana Islands for more than 60 years. Exercises range from large, 10-day long joint multi-strike group exercises using multiple surface vessels, submarines and aircraft, to multi-hour exercises designed to target specific skills or weapons systems, such as missile tracking. Some exercises involve explosives.