On the shores of the Chesapeake Bay and the Atlantic Ocean in the Washington region, troubling signs have been spotted indicating that all is not well with one of the most popular species of mammals with which humans share the planet.

More than the expected number of dead dolphins have washed up. “It has definitely been unusual,” said Kate Hendrickson, spokeswoman for the National Aquarium in Baltimore.

Usually, according to Virginia aquatic animal specialists, an average of 64 bottlenose dolphins are picked up on or near shore in a year.

But this year, the Virginia Aquarium Stranding Response Team said it has been called to the scene of the stranding of 82 dolphins.

Last month alone, the team counted 44 dead dolphins. The average number for the month is seven, according to an online post by the stranding team.

The cause of the deaths has not been determined, the group said.

Many of the animals have decomposed too much to provide much information.

Jennifer Dittmar, the stranding coordinator for the Baltimore aquarium, provided figures indicating a similar trend.

She said Maryland’s natural resources department has recorded 15 dolphin deaths this year, with seven coming last month. Some dolphins were apparently found on the shores of the bay and others in the ocean.

She said data from the National Oceanic and Atmospheric Administration indicates that there has been an increase in dolphin mortality along the Atlantic coast.

As in Virginia, she said, many of the dolphin carcasses were “pretty decomposed.” But, she said, tissue samples from some of the more recent deaths have been sent for analysis to find a possible cause.

The Virginia group said in its posting that it would take time for results of its tissue samples to arrive. Even then, the group said, “they may be inconclusive.”

According to the Virginia group, the most recent strandings there appeared to be almost exclusively male, with all ages and sizes represented.

According to NOAA, the bottlenose dolphin, which is found along the North Atlantic coast of the United States, can range in weight from 300 to 1,400 pounds and normally lives for up to 40 to 50 years. They are protected under the Marine Mammal Protection Act of 1972.

In a related matter, the National Aquarium completed on July 12 its annual one-day count of dolphins off Maryland’s Atlantic coast.

The number spotted, in a three-hour “snapshot” , made by observers at four places along shore, was 113, which Dittmar said was about average.