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Deepwater dolphin strands during SoCal sonar exercises

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Dolpin Strands on Navy Island at End of Recent Sonar Exercises – A single deep-water Northern right whale dolphin was found live-beached on San Nicolas Island on January 29, during a heavily scrutinized Naval training exercise. Navy personnel returned it to the water several times, but it did not survive. Curators at the Santa Barbara Museum of Natural History worked all night to perform a necropsy because clues are lost to rapid decomposition. The head was removed and refrigerated, then taken to the nearby Alamo Pintado Equine Medical Center for magnetic resonance imaging. “At this point, we cannot rule in or rule out sonar or any other kind of intense noise,” said Teri Rowles, a veterinarian with the National Oceanic and Atmospheric Administration and head of the nation’s Marine Mammal Health and Stranding Response Program. Rowles said the initial review confirmed increased fluid in the ears. “That could be blood; it could be infection or parasites — those are the three more common causes of fluid in the ears,” she said. Or it could be trauma related to sonar, though Rowles cautioned against jumping to conclusions until more detailed studies are completed. “The lesions that we have seen to date are consistent to what has been found in whales in the Canary Islands and the Bahamas,” Rowles said. More conclusive results will not come until pathologists can complete microscopic examination of the brain, the ears, and other tissues to look for gas or fat bubbles and related hemorrhaging. Such injury has been termed “gas and fat embolic syndrome,” and is considered nearly synonymous with sonar exposure injuries, though it is not entirely clear whether the sound, or a behavioral reaction such as changed dive patterns, causes the damage. The microscopic analysis of most tissues should take about a month, Rowles said. It could take as long as a year to examine the ears because the bones must be slowly dissolved in fluid to reveal soft tissues inside. Previous sonar-induced strandings have involved multiple animals; northern right whale dolphins live in groups of 100-1000 animals, making this single stranding somewhat unusual. A Navy spokesman said that the nearest ship using mid-frequency active sonar was 62 miles away the previous day, and was not part of the exercise. Source: LA Times, 2/22/08 [READ ARTICLE]

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