Thirteenth right whale found dead in waters near Cape Cod

A right whale found dead in waters near Cape Cod this week has been identified as a frequent visitor to the area that was first spotted off the Cape in 1992.

The Cape Cod Times reports the 26-year-old female whale named Couplet was identified Thursday through photos in a database at the New England Aquarium.

It was at least the 13th North Atlantic right whale to be found dead this year off the coasts of Canada and Massachusetts. Couplet's carcass was discovered Monday. 

The cause of death is under investigation.

Right whales are among the most imperiled marine mammals. No more than 500 of them still exist in the wild.

Experts say some of the dead whales showed signs of being struck by ships or entangled in fishing lines.