The U.S. Navy has been given authorisation to impact whales and dolphins while conducting their sonar training exercises around the main Hawaiian Islands. The letter of authorisation and accompanying rules from NOAA's Fisheries Service allow for injury or death of up to 10 animals of each of 11 species over the next five years covered by the regulations.

The exercises can range from large multi-national, month-long training exercises using multiple submarines, ships, and aircraft conducted every other year, known as Pacific Rim Training Exercises, to two- to three-day exercises to test the readiness of battle groups, known as Undersea Warfare Exercises, and shorter exercises that last less than a day.

The Navy requested authorisation under the Marine Mammal Protection Act because mid-frequency active sonar can emit continuous sound well above 235 decibels and has the potential to affect the behaviour of some marine mammals including temporary loss of their hearing.

Some protective measures outlined by NOAA include the Navy establishing marine mammal safety zones around each vessel using sonar and shut down sonar operations if dolphins and whales are seen within designated safety zones. They must use exclusion zones to ensure that explosives are not detonated when animals are detected within a certain distance and also implement a stranding response plan that includes a training shutdown provision in certain circumstances and a memorandum of agreement to allow the Navy to contribute in-kind services to NOAA's Fisheries Service if the agency has to conduct a stranding response and investigation. NOAA Fisheries Service said in a statement that these measures "should minimise the potential for injury or death and significantly reduce the number of marine mammals exposed to levels of sound likely to cause temporary loss of hearing."

The regulations establish an area of extra caution in the Maui Basin because of its high density of humpback whales. The Hawaiian Islands National Marine Sanctuary covers the four island area of Maui; Penguin Bank; and extends off the north shore of Kauai, the north and south shores of Oahu, and the north Kona and Kohala coasts of the Big Island. Hawaii is one of the few areas where humpbacks breed, calve, and nurse their young. Approximately 4,000-5,000 whales migrate to the Hawaiian Islands each winter. Although the population of humpbacks is increasing, these whales remain endangered.

NOAA's Fisheries Service acknowledges that exposure to sonar has been associated with the stranding of some marine mammals, and some injury or death could occur.