The USS Shoup did not kill or hurt marine mammals when it used its sonar in May during routine training in Haro Strait, a just-released Navy report concludes.
The inquiry comes on the heels of a preliminary report published Monday by the National Marine Fisheries Service that studied the deaths of 11 porpoises that washed ashore near the time the Shoup passed through the strait.
While some whale watchers and marine mammal experts thought the porpoise strandings were tied to the Shoup’s passage through the area between Vancouver Island and San Juan Island, the fisheries service report was inconclusive. It said scientists could not find any definitive evidence of ear damage in the porpoises that could be linked to the Shoup’s sonar.
The Navy report, however, was more clear-cut.
It took a broader view of the Shoup’s use of sonar in Haro Strait on May 5, said Navy Rear Adm. Len Hering, commander of Navy Region Northwest.
The Shoup’s sonar, the Navy report said, apparently did not affect orcas or other marine mammals near Haro Strait. And the destroyer did not cause a mass stranding of porpoises.
While the potential exists that Navy sonar can harm marine mammals, Hering said, that wasn’t found in the Shoup incident. The porpoises found dead probably didn’t die from their exposure to the Shoup’s sonar.
"There is a potential. But for this particular incident, the possibility of us having created any of these deaths is pretty slim," Hering said.
Whale experts who had been critical of the Navy when the National Marine Fisheries Service’s report was released said they couldn’t comment on the Navy report because they hadn’t read it yet.
The Navy analysis was led by investigators from the Pacific Fleet. It included the results of the previous report, but went further. It also relied on three independent sound studies using the Naval Undersea Warfare Center in Newport, R.I., the Naval Research Laboratory, and anti-submarine warfare experts from the Pacific Fleet to determine just how damaging the noise level from sonar was at the time of the Shoup’s training exercise.
While the fisheries report focused on what killed the 11 porpoises brought in for necropsies, the Navy report detailed where the marine mammals were found, and when.
Seven porpoises died before the Shoup ever left the pier at Naval Station Everett, the report said. Eight others found stranded were discovered up to three weeks after the Shoup had left the area.
One porpoise could be linked to the time the Shoup was training near San Juan Island. But the report said the necropsy on the mammal found no evidence of ear damage.
The inquiry also said the Shoup’s sonar did not harm killer whales in the area.
That’s significant, because southern resident orcas were designated a depleted stock by the National Marine Fisheries Service last year. The agency has begun work on a recovery plan to restore the orcas, an icon of the Pacific Northwest.
The Shoup came closest to the orca J-Pod as it passed Andrews Bay on San Juan Island in Haro Strait just after 2:30 p.m. May 5. The killer whales were about 1.5 nautical miles away, and experts who reviewed videotapes of the orcas taken as the Shoup passed by said the orcas appeared to act normal.
The Shoup returned to Everett from training on Tuesday. An Oscar Austin-class guided-missile destroyer, it’s the only Navy ship in Puget Sound that uses midrange frequency sonar.
Overall, Hering said, active sonar isn’t used often by Navy ships.
"We don’t like to use active sonar, It’s like a flashlight in the middle of a field," he said. "We prefer to do 99.9 percent of our acoustic work in the passive mode."
Hering said the Navy is committed to continuing its research on the effects of sonar on marine mammals. The Shoup will still need to get approval from the Pacific Fleet before using sonar in Puget Sound.
"The Navy will continue to look at the process for how we conduct operations at sea. We will always make sure that the Marine Mammal Protection Act is at the forefront of our decision-making process," he said.
Reporter Brian Kelly: 425-339-3422 or kelly@heraldnet.com.
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