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GOVERNMENT REPORT ON MASS WHALE STRANDING IN N.C. IDENTIFIES NAVAL SONAR AS POSSIBLE CAUSE
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."
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Q. What does the North Carolina event have in common with previous mass strandings known to be associated with sonar? How does it differ?
A. According to the report, the North Carolina event shares "a number of features" with sonar-related events in other parts of the world. It involved several different offshore species, and most of the whales stranded alive and were broadly distributed, with no sign of infectious disease. During at least one of the transmissions, which occurred the day before the strandings occurred, a "surface duct" seems to have been present, forming a natural acoustic channel in the water that helped propagate the sound. The same condition was present during the 2000 mass stranding in the Bahamas.
The North Carolina event differs from previous strandings primarily in providing no sign of the "bends"-like trauma seen in deep-diving beaked whales. Sonar does not appear to have induced the same physiological symptoms in these species; as NMFS acknowledges, however, it could have caused the strandings by affecting the animals' behavior.
Q. The Navy was operating sonar in the area for just a few minutes to a few hours each day before the strandings occurred. Is that sufficient time to do this kind of damage?
A. Yes. The whales that died in the best-documented incident to date -- a stranding that took place in the Bahamas, in 2000 -- were exposed to moderately intense sounds (over 160 dB) for no more than 30 seconds. In Greece, whales began to strand during a single 3-hour run by a single sonar vessel. Under the right circumstances, it does not appear to take long for sonar to harm marine mammals.
Q. What does all this mean for the debate over the Navy's proposed Undersea Warfare Training Range in North Carolina? The Navy has said it would reopen the public comment period if any significant new information emerged on these strandings. Do you think the information presented in NMFS' report rises to that level?
A. In its draft environmental impact statement, the Navy does not even consider the possibility that sonar caused these strandings, or could cause any whales to die off North Carolina. This position is insupportable. NMFS itself has told the Navy that, in light of various sonar-related events, "the Navy should seriously reconsider the potential for mortality of cetaceans due to strandings related to activities in [the training range]" (NMFS' Jan. 31 comments on the proposed range). While the information presented today is not conclusive, it indicates that sonar may have caused these strandings as well -- and underscores the need to properly evaluate the risk of mortalities on the range.
Related NRDC Pages
Protecting Whales from Dangerous Sonar
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