Every year, at least some dead dolphins wash up onto beaches. Some get hit by boat propellers. Others get caught in fishing nets. Still others succumb to viruses, bacteria, lungworms, fungal infections and other diseases.
From 2007 to 2012, according to NOAA data, between 88 and 113 dolphins washed ashore in the area of the current East Coast die-off. As of last week, the current tally is 299, with a large spike since early July.
In New Jersey, there are usually between half a dozen and dozen strandings each year, said Bob Schoelkopf, founding director of the Marine Mammal Stranding Center in Brigantine, N.J. So far this year, there have been 74 dead dolphins found on the state's beaches. In Virginia, there were 45 strandings last month, compared to the state's annual average of just seven in July.
Accidents with boats and commercial fisheries leave telltale signs on dolphin corpses, Schoelkopf said, allowing experts to rule those out as possible explanations for the recent rash of deaths. Water quality and temperature also appear normal this year.