The Report Also Excludes Most Other Potential Causes
LOS ANGELES (March 29, 2006) -- A report today by the National Marine Fisheries Service (NMFS) on the 2005 mass stranding of whales in North Carolina identifies sonar operated by the U.S. Navy as a possible cause of the incident. The report also excludes most other causes. The following is a statement about the report by Michael Jasny, a senior consultant to NRDC:
"Today's report by the federal government establishes that sonar was a possible cause of the January 2005 mass stranding in which 37 whales of three different species died, and that most other possible causes were not in play.
"The report establishes that sonar was used in the vicinity of the strandings and that the timing was right for sonar to have caused them. It confirms that the event itself was highly unusual, being the only mass stranding of offshore species ever to have been reported in the region; and that it shared 'a number of features' with other sonar-related mass stranding events (offshore species, stranding alive, atypically distributed). Finally, investigators appear to have eliminated many other potential causes, including viral, bacterial, and protozoal infection, direct blunt trauma, and fishery interactions.
"However, it is rare that a stranding investigation gives definitive proof of a connection with sonar. The report released by NMFS today shows once again that this problem endemic to stranding investigations remains true.
"We sometimes know when sonar has killed marine mammals because it leaves a calling card: bleeding around the brain, holes in the organs, symptoms similar to those seen in human divers with 'the bends.' That is what we have seen in deep-diving beaked whales. But in other species the signs are less clear. Sonar can cause animals to strand simply by disorienting them; by comparison to the beaked whale strandings, however, those cases are more difficult to prove.
"Thus, while NMFS has concluded that sonar may have caused the North Carolina strandings by affecting the whales' behavior, and has pointed to some suggestive evidence, we will probably never know for certain.
"In a related matter, the scientific journal 'Nature' reports today on a mass stranding of beaked whales that occurred along the Costa del Sol in southern Spain this January ("More whale strandings are linked to sonar"). Scientists investigating these strandings have concluded that a noise event, probably naval sonar, was the 'most likely' cause of those deaths."