SAN JOSE, Peru, April 4, 2012 - A catastrophe has hit the dolphins of Peru. Hundreds of them have washed ashore dead between San Jose and Piura on the country's north coast.
Hardy Jones, executive director of BlueVoice.org and Dr. Carlos Yaipen Llanos of ORCA Peru covered 135 kilometers of beach running north from the fishing village of San Jose. They counted 615 dead dolphins ranging in age from newborns to fully mature males. Most of the dead are of the species long beaked common dolphins (delphinus capensis).
"If you can count 615 dead dolphins you can be sure there are a great many more out at sea and the total will reach into the thousands," said Jones.
ORCA's study of the dolphin die-off was sanctioned by the Peruvian Ecological Police.
The die-off, or Unusual Mortality Event (UME), was first noticed in January by fishermen who reported it to authorities. So far there is no definitive explanation for the extraordinary mass mortality. However initial tests conducted by Dr. Yaipen Llanos show evidence of acoustical impact from sonic blasts used in exploration for oil. "But I hasten to state that we have no definitive evidence of what is killing the dolphins," said Dr. Yaipen Llanos.
Dolphins have highly sensitive auditory systems and loud noises essentially blind them. No signs would be visible on the exterior of the dolphin. Damage to the inner ear could only be detected through necropsy of the inner ear. "It is a horrifying thought that these dolphins would die in agony over a prolonged period if they were impacted by sonic blast," said Jones.
The United States government agency that governs permits for oil exploration has just prohibited similar sonic tests in an area of the Gulf of Mexico where dolphins are calving.
Other possible explanations for the Peruvian UME include viral infection and toxins produced by algal blooms. However Dr. Yaipen Llanos's initial forensic investigations found no lesions that would justify a cause of toxic poisoning.
The UME in Peru represents one of the largest mass die-offs of marine mammals ever recorded. But it is not unique. During the period of 1987 – 88 hundreds of dolphins washed ashore along the east coast of the United States. And during the period thousands of seals died in northern Europe from a cause that was eventually determined to be distemper virus.