On the morning of July 3, 2004, approximately 200 melon-headed whales came near the shore of Hanalei Bay, on the Hawaiian island of Kauai. Around the same time the whales were spotted in Hanalei Bay, RIMPAC exercise participants began conducting anti-submarine warfare exercises about 20 to 60 nautical miles from the Bay. At the request of the National Oceanographic and Atmospheric Administration (NOAA), the exercises involving active sonar were suspended that afternoon as a precaution. The whales were “herded” out of the bay the next day by volunteers in canoes and kayaks. Two days later, NOAA Fisheries reported finding one juvenile whale that had been separated from the pod and that had subsequently died of malnutrition.
According to the NOAA Fisheries report into the Hanalei Bay incident, it was not possible to determine whether sonar was the cause of this incident. Furthermore, the report did not conclude that there was a causal relationship between the incident and the use of sonar. As a clarification, one of NOAA’s authors stated “that there may have been a number of coincident factors (one of which may have been active sonar) that ultimately resulted in the stranding event.”
Here is the final NOAA report on the incident.