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News | March 29, 2006

No Definitive Cause for 2005 North Carolina Stranding: Injuries Not Consistent With Sonar Use

Navy News Service

The National Oceanic & Atmospheric Administration (NOAA) released the final National Marine Fisheries Service (NMFS) report March 29 regarding the marine mammal stranding that occured at Oregon Inlet, N.C. on Jan. 15, 2005.

NOAA's investigation found no physical evidence of sonar involvement in the stranding. 

Highlights of the examination findings include the following: 

  • NMFS investigators did not find commonalities in injury across species that would indicate a single cause for the event.
  • Gas emboli lesions, or bubbles similar to "the bends," which some have associated with past sonar-correlated strandings of beaked whales, were not found. 
  • Differences in operational and environmental characteristics exist between this event and previous events where sonar apparently played a role. 
  • Evidence supporting a definitive association with sonar is lacking in this event.

"The NOAA report clearly acknowledges that there is no pathology implicating sonar as a cause of the stranding," said Rear Adm. James Symonds, director of the Navy's environmental programs. "We continue to remain sensitive to environmental concerns during our training and operations. 

"We recognize and appreciate the fact that NMFS had to meticulously consider all possibilities for why these animals stranded," he added. "We believe the timeframe and the distance at which active sonar was used, two to three days prior to the stranding and over 50 nautical miles from Oregon Inlet, make it extremely unlikely that our sonar affected the animals in any way." 

There are many well-documented causes of whale strandings, and scientists are learning more every year. The NOAA report noted that "environmental conditions, including strong winds, changes in upwelling- to downwelling-favorable conditions, and gently sloping bathymetry were consistent with conditions which have been correlated with other mass strandings." These factors, combined with pollution, commercial shipping, fishery entanglements, disease, parasite infection, trauma, and other natural factors, lead to a rate of approximately 3,500 strandings every year on U.S. shores, according to NOAA's Web site. 

While continuing to train to meet its national security requirements under U.S. law, the Navy remains dedicated to the stewardship of ocean resources. The Navy continues to work with NOAA toward this mutual goal, including environmental planning efforts for future training exercises. The Navy also implements protective measures to minimize the potential for sonar to affect marine mammals at sea, and funds ongoing scientific research to better understand how marine mammals are affected by sound.