Mass dolphin deaths in Peru caused by acoustic trauma
BY CANDACE CALLOWAY WHITING MAY 17, 2012 IN ENVIRONMENT Dr. Carlos Yaipen Llanos of ORCA in Peru informed Hardy Jones of Blue Voice that acoustical trauma is the cause of the Mass Mortality Event (MME) that killed an estimated one thousand dolphins along the coast of northern Peru in March 2012.
In her article, Hundreds of dead dolphins wash up along the coastline in Peru, Elizabeth Batt describes the devastating loss of the dolphins and porpoises, and the swift action by filmmaker and author Hardy Jones to document the event.
Now the necropsy results are in, and there is unequivocal evidence that the dolphins were killed by an acoustic trauma, such as loud sonar or explosive blasts (more information on potential sources of the loud sound in that region can be found here). Dr. Llanos doesn’t identify the source of the trauma, but all other tests (virus, contaminants, parasites etc) are not considered factors.
The following tissue samples, provided to Blue voice by Dr. Llanos show evidence of rapid ascent, (though the scientists are not willing to speculate on what caused the dolphins to race to the surface, their bodies are adapted to adjust to depth, and normally do not aggregate bubbles in their tissues).
Bubbles replaced normal tissue in the dolphin’s liver.
A large bubble is compressing a vein and artery in this dolphin’s bladder.
The jaw blubber of this baby porpoise is spread by bubbles. The blood vessels show congestion and hemorrhage.
Blue Voice Necropsies were performed on site. Macroscopic findings include: hemorrhagic lesions in the middle including the acoustic chamber, fractures in the periotic bones, bubbles in blood filling liver and kidneys (animals were diving, so the main organs were congested), lesion in the lungs compatible with pulmonary emphysema, sponge-like liver. So far we have 12 periotic samples from different animals, all with different degree of fractures and 80% of them with fracture in the right periotic bones, compatible with acoustic impact and decompression syndrome.
In a February stranding in the same region of Peru, Dr. Llanos found that:
10 of the 17 animals found dead had broken periotic bones, that is, due to acoustic impact. The source of the impact was from the right side of the pod, since hemorragic internal ear was found in the right side of the stranded animals.
We know that the use of dynamite is common among fishermen, and that fishermen are taking the meat of the stranded dolphins. This could be the cause of death of the animals…however, the signs do not correspond to that of explosive impact in their bodies. We talked today with people from the oil company and they say they haven’t performed any seismic exploration in the area this month. However, here in Peru these companies don’t need to do the seismic assessment themselves. Update 5/18/12 : Dynamite has been ruled out as a possible cause (via Hardy Jones),
To compare with some of the stranded dolphins Dr. Llanos examined the remains of healthy dolphins that had been stabbed at sea and eaten by the local fishermen and found “intact periotic (ear) bones, (with no fractures), so it was a good “control” sample to compare with previously collected (and fractured) ones.”
Hardy Jones explained to Digital Journal that “traveling to and within Peru is expensive and testing samples from the dead dolphins is very costly, yet highly important.” Blue Voice and Dr. Llanos (ORCA) will continue to investigate the mortality event, and will post updates.
It doesn’t happen often that whales can be returned to the ocean after stranding, but thanks to the dedicated effort of authorities and trained volunteers this young gray whale is among the lucky few. Please be aware that NOAA is facing budget cutbacks, and their ability to help whales and dolphins in need will be curtailed without funding. Please see this page, and contact your legislators (contact information is provided).
Information on the rescue provided by NOAA spokesman Michael Milstein:
A rescue effort during high tide late Friday night freed a young gray whale that had been stranded on a remote beach in Olympic National Park and Olympic Coast National Marine Sanctuary for about three days.
Responders from NOAA Fisheries’ West Coast Marine Mammal Stranding Network and Olympic National Park fashioned a harness around the whale linked to pulleys anchored lower on the beach and on the shore. Experts from Cascadia Research Collective, SR3 [SeaLife Response, Rehabilitation, and Research] , and the Washington Department of Fish and Wildlife led responders in using the pulley system to turn the whale seaward and pull it into deeper water.
The team also dug a shallow trench around the whale to help float and position the whale as the tide came in. They had hoped the especially high tide at 10:19 p.m. would give the 24-foot whale its best chance of returning to the open ocean.
“The mission at one point seemed like it was failing with little progress made and the whale not seeming to be able to help and even appearing to turn back toward shore,” said John Calambokidis of Cascadia Research Collective. “Then, at the last possible moment, with the whale in about four feet of water in the surf and the harness released, the whale started to swim.”
“A cheer went up in the darkness and the assembled team stood shining lights into the darkness and mist, stunned at the apparent turn of events and success,” Calambokidis recalled.
Experts estimated the whale as one to two years old, and in fair condition. Although the whale was earlier described as female, it is now believed to be a male. The whale remained alert throughout the stranding and tried aggressively to free itself several times during earlier high tides.
Historically it is unusual for large stranded whales to be successfully freed. The National Park Service and NOAA Fisheries thank the many volunteers and staff who assisted in the response.
“Whales are not designed to be out of water so their organ systems rapidly decline when beached and medical care is essential,” said Lesanna Lahner, wildlife veterinarian from SR3, a marine mammal rescue organization. “To help him over these hurdles, supportive medications such as B vitamins and anti-inflammatories were administered.”
Lahner and Washington Department of Fish and Wildlife marine mammal biologist Dyanna Lambourn administered the medications.
NOAA Fisheries removed gray whales from the endangered species list in 1994 and estimates the population that migrates along the West Coast of the United States at about 20,000. Gray whales typically travel north from their Mexican breeding grounds to Arctic feeding grounds in spring and early summer.
Gray whales are unusual among whales in that they regularly feed in shallow waters. Several gray whales have been seen in recent months feeding in the vicinity of the stranding, which is in Olympic National Park and Olympic Coast National Marine Sanctuary.
Rescuing large whales is inherently dangerous for both the animals and responders, and members of the marine mammal stranding network are highly trained in marine mammal biology and health, safety protocols, and emergency response procedures. NOAA Fisheries reminds the public not to approach stranded marine mammals and instead report them to the West Coast Marine Mammal Stranding Network hotline at 1-866-767-6114.